B-Complex Formulas

Q: Does a B-complex give you energy?

B vitamins help the body release energy from food, but this normal role does not show that extra amounts raise energy when intake is enough. One very small trial of a four-vitamin tablet reported longer running time in healthy young adults. A review found too little data on everyday tiredness to judge.

Q: Is methylated B12 or folate better?

Not shown for health outcomes. One trial found the methyl form of folate raised red blood cell folate more than folic acid. A review says the two act alike at equal molar amounts. A review of B12 forms gives no head-to-head result in its abstract.

Q: Does a B-complex help with stress or mood?

A 2019 pooled review found a small benefit for stress, no clear benefit for depression and none for anxiety. Results were low-certainty and some authors report industry funding.

Q: Does it help memory?

Reviews found no benefit for thinking skills from B12 alone or B complex in people without deficiency, and a Cochrane review found B vitamins probably have little or no effect on overall thinking in healthy older adults.

Q: Does it protect the heart?

A Cochrane review of 15 trials found no difference in heart attack or death from any cause; stroke was slightly lower, near the edge of chance. Folic acid trials found no effect on vascular events, cancer or death.

Q: Why does niacin cause flushing?

MedlinePlus describes flushing as warmth, redness, itching or tingling of the face, neck, arms or upper chest, reported when niacin is given for high cholesterol. Nicotinamide does not appear to cause it. The NHS says high-dose nicotinic acid can also harm the liver over time.

Q: Can too much vitamin B6 be harmful?

Yes. A 2023 review says higher B6 levels, usually from supplements, can cause a sensory nerve damage. The NHS says 200 mg or more a day can cause numbness in the arms and legs, sometimes permanent, and advises no more than 10 mg a day in supplements unless a doctor advises.

Q: Can folic acid hide B12 deficiency?

The NHS says more than 1 mg a day of folic acid can hide the symptoms of B12 deficiency, a particular concern for older people. A 2024 review calls the evidence mostly correlative but enough to watch for B12 deficiency.

Q: Can biotin affect blood tests?

Yes. High biotin can cause falsely high or low results in some laboratory tests, depending on the test and the maker. Tell the doctor or lab you take it.

B-complex products (several B vitamins in one product) · also called Vitamin B complex, B-complex, complejo B, vitaminas del complejo B

B-complex products combine several of the eight B vitamins in one tablet, capsule, gummy or drink. No trial tested these finished products for most of the claims on labels. Pooled trials of B vitamins found a small stress benefit, no thinking or memory benefit in people who are not deficient, and no effect on heart attacks. The main cautions are vitamin B6 nerve damage, niacin flushing, folic acid hiding B12 deficiency, and biotin changing blood tests.

General information, not medical advice. Last substantive update October 26, 2026 · Not medically reviewed. A named clinician has not signed off on this page. How this page is made

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About B-Complex Formulas

B-complex products bundle several B vitamins. No trial of a finished product settles most label claims. Stress benefit is small, memory benefit is not found in people who are not deficient, and 'methylated' is not shown to be better. B6, niacin, folic acid and biotin each carry specific cautions.

What a B-complex product is

A B-complex product combines several of the eight B vitamins: thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), B6, biotin (B7), folate or folic acid (B9) and B12.

Which ones it holds, in which forms and in what amounts, differs from product to product. Some are sold as capsules or gummies, some as powders or drinks. Read the Supplement Facts panel.

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What is usually inside, and in which forms

Niacin may be nicotinic acid, which can cause flushing, or nicotinamide, which does not appear to (MedlinePlus). B6 may be pyridoxine or its active form, pyridoxal-5'-phosphate. Folate may be folic acid (synthetic) or methylfolate (5-MTHF). B12 may be cyanocobalamin or methylcobalamin.

'Methylated' on a label usually means methylfolate and methylcobalamin. One 24-week trial found the methyl form of folate raised red blood cell folate more than equal-molar folic acid. No source read compared health outcomes, and the finding is about folate only. Each B vitamin has its own page under Related.

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Who these products are sold to

They are marketed for energy, stress, mood and memory, the claims this page checks, and to people who think their diet is short on B vitamins. The NHS says most people can get what they need from a varied diet. B12 is not naturally in plant foods, so vegans may not get enough (NHS). Older people absorb B12 less well (NHS).

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Reading the label

Supplement Facts lists each vitamin with its amount and a percent Daily Value (%DV). The FDA says the Daily Value is the reference amount and %DV shows how much one serving contributes. Label Daily Values for the B vitamins include biotin 30 mcg, folate 400 mcg DFE, niacin 16 mg NE, pantothenic acid 5 mg, riboflavin 1.3 mg, thiamin 1.2 mg, B6 1.7 mg and B12 2.4 mcg. These are label reference values, not advice.

Check the form of niacin and folate, whether a 'proprietary blend' hides amounts, and what a serving means (one gummy or two). Gummies and drinks have their own pages.

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What the research shows

For stress, a 2019 review of 16 trials found a small benefit and no clear benefit for depression or anxiety. For memory and thinking, reviews of B12 and B complex found no benefit in people without deficiency. For energy, one very small trial of a four-vitamin tablet reported longer running time; everyday tiredness is untested.

For the heart, a Cochrane review of 15 trials found no difference in heart attack or death from any cause; stroke was slightly lower. Evidence for 'methylated' being better is limited to blood folate.

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Food versus pills

The NHS names food sources for each B vitamin: for example meat, fish, eggs, milk, wholegrains, peas, nuts and leafy greens. Amounts per portion were not read from USDA or NIH, so none are stated.

The trials here tested pills, not foods. No trial comparing food B vitamins with pills was read.

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At a glance

Traditional uses history, not proof

B vitamins are sold to support energy, mood and nerves
Methylated 'active' forms are sold as an alternative to folic acid and cyanocobalamin

Studied for research

Stress ratings, low certainty
Thinking and memory in people without deficiency, evidence against
Energy and exercise endurance, insufficient evidence
Heart attack and stroke, mixed evidence
Methylfolate versus folic acid for blood folate, low certainty
Folic acid before pregnancy, supported by the NHS

Main compounds

Thiamin (B1)
Riboflavin (B2)
Niacin (B3)
Pantothenic acid (B5)
Vitamin B6
Biotin (B7)
Folate or folic acid (B9)
Vitamin B12

Common forms

Tablets and capsules
Gummies
Powders and drinks
Methylated forms (methylfolate, methylcobalamin)
Ordinary forms (folic acid, cyanocobalamin)

Research links: 2021 review: B12 and B complex for thinking, mood and fatigue (16 trials) · 2019 review: B vitamins for stress, mood and anxiety (16 trials) · 2017 Cochrane review: homocysteine-lowering B vitamins and heart events · 2023 review: vitamin B6 and nerve damage · 2020 laboratory guidance: biotin and blood tests · Research Library · Genes & Biomarkers Library

What it is and its history

Accepted scientific name: B-complex products (supplements that combine several B vitamins)
Common names: B-complex (English); Vitamin B complex (English); B vitamins (English); Complejo B (Spanish); Vitaminas del complejo B (Spanish)
Family or group: Product type. The NHS lists eight B vitamins: thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid, B6, biotin (B7), folate or folic acid and B12.
Look-alikes and adulterants: Name: Multivitamin; Note: Adds many vitamins and minerals beyond the B group. Has its own page.; Name: Single B vitamins; Note: One B vitamin on its own, such as B12 or folate. Each has its own page.; Name: Energy drinks, shots and gummies; Note: Often contain B vitamins with caffeine or sugar. Have their own page.; Name: Prenatal vitamins; Note: Contain folic acid and other nutrients for pregnancy. Have their own page.
Sustainability and conservation: Not assessed.

Traditional use and history history, not clinical proof

Tradition or era	Documented use	Source
1940s to 1950s: folic acid for pernicious anaemia	A 2024 review says high-dose folic acid (above 5 mg a day) was used then to reverse the anaemia of B12 deficiency from pernicious anaemia, but this hid the B12 deficiency and may have worsened nerve damage. The practice was stopped in the 1970s.	p38987872

Traditional use shows how it was used. It does not show that it works or is safe today.

What is inside, and how it may work

What it contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.

Main compounds

Compound	Family	Where it is concentrated	Activity studied	Level of evidence
Thiamin (vitamin B1)	B vitamin	Not read from a source.	NHS: helps the body break down and release energy from food and keeps the nervous system healthy. Food sources named: peas, some fruits, nuts, wholegrain bread, fortified cereals, liver. ²⁷	Human data
Riboflavin (vitamin B2)	B vitamin	Not read from a source.	NHS: keeps skin, eyes and the nervous system healthy and helps release energy from food. Food sources named: milk, eggs, fortified cereals, mushrooms, plain yoghurt. ²⁷	Human data
Niacin (vitamin B3): nicotinic acid and nicotinamide	B vitamin; two forms	Not read from a source.	NHS: helps release energy from food and keeps the nervous system and skin healthy. Nicotinic acid can cause flushing; nicotinamide does not appear to (MedlinePlus). Food sources named: meat, fish, wheat flour, eggs. ^{27 26}	Human data
Pantothenic acid (vitamin B5)	B vitamin	Not read from a source.	NHS: helps release energy from food. Food sources named: chicken, beef, liver and kidneys, eggs, mushrooms, avocado. ²⁷	Human data
Vitamin B6 (pyridoxine; active form pyridoxal-5'-phosphate)	B vitamin	Not read from a source.	NHS: helps the body use and store energy from protein and carbohydrate and form haemoglobin. Food sources named: pork, poultry, some fish, peanuts, soya beans, wheatgerm, oats, bananas, milk. ^{27 15}	Human data
Biotin (vitamin B7)	B vitamin	Not read from a source.	NHS: needed in very small amounts to help the body make fatty acids; found in a wide range of foods at very low levels. High doses can disturb some blood tests. ^{27 9}	Human data
Folate, folic acid and methylfolate (5-MTHF)	B vitamin; natural, synthetic and 'methyl' forms	Not read from a source.	NHS: folate helps form red blood cells and lowers the risk of neural tube defects; folic acid is the manmade form. Pietrzik review: folic acid is synthetic and must be converted in cells; L-5-methyl-THF is the main natural form and the form found in blood. Food sources named: broccoli, Brussels sprouts, leafy greens, peas, chickpeas and kidney beans, liver, fortified cereals. ^{27 16}	Human data
Vitamin B12 (cyanocobalamin, methylcobalamin, adenosylcobalamin)	B vitamin; synthetic and natural forms	Not read from a source.	NHS: helps make red blood cells, keeps the nervous system healthy, releases energy from food and helps the body use folate. Food sources named: meat, fish, milk, cheese, eggs, fortified cereals; the NHS says vegans may not get enough. ^{27 2}	Human data

Mechanisms, receptors and pathways

Target or pathway	Gene or receptor	What was found	Level
Release of energy from food	Not specified in the sources read	The NHS says thiamin, riboflavin, niacin, pantothenic acid and B12 help the body release energy from food, and B6 helps it use and store energy from protein and carbohydrate. This describes a normal role. It does not show that extra amounts raise energy when intake is enough. ²⁷	Human data
Homocysteine handling	MTHFR, MTR and MTRR genes (named in the 2024 trial)	Homocysteine is an amino acid in methionine handling (Cochrane). Folate, B6 and B12 lower it in trials. A 2024 trial of a methylated blend studied people with variants in MTHFR, MTR and MTRR; in a 2023 trial the MTHFR 677TT variant went with a larger fall in homocysteine. ^{11 17 13}	Human data
Biotin binding in laboratory tests	Not applicable	Some blood tests rely on biotin binding. High circulating biotin can produce falsely high results in competitive tests and falsely low ones in sandwich tests. ⁹	Laboratory

Absorption, metabolism and elimination

Absorption: A 2025 review says supplements raise blood B12 to a similar extent as dietary B12 in healthy people. The NHS says B12 absorption gets harder with age. In one trial the methyl form of folate raised red blood cell folate more than equal-molar folic acid.
Distribution: Not found.
Metabolism: Folic acid is synthetic and must be reduced to the active form inside cells; L-5-methyl-THF is the main form found in blood (review).
Elimination: MedlinePlus says water-soluble vitamins such as niacin are not stored in the body and leftover amounts leave in urine. The biotin guidance says biotin is eliminated relatively fast.
Bioavailability: B12 forms were not compared in the sources read. Folic acid and 5-MTHF are comparable at equal molar amounts (review) with one trial showing a larger red blood cell folate rise for the methyl form.

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Isolated compounds versus whole extracts

B vitamins in foods come with protein, fibre and other nutrients, and the NHS says most people get what they need from a varied diet. Trials on this page tested pills, not foods. Food sources named by the NHS are listed under each vitamin. B12 is not naturally in plant foods, so vegans may not get enough from diet alone (NHS).

Nutritional composition

No USDA or NIH amounts of B vitamins per food portion were read for this page, so no food amounts are stated; foods are named from the NHS page. Label Daily Values are from the FDA page read. A B-complex pill and a food are not the same thing.

10benefits and uses looked at

28studies and sources checked

Low certaintybest evidence rating found

4lab markers tracked in trials

1 mixed findings6 low certainty2 not enough evidence1 evidence against

What was looked at

The 10 benefits and uses checked for B-Complex Formulas, each with how strong the evidence is. Tap one to open it.

Stress and moodLow certainty
Thinking skills and memoryEvidence against
Energy, tiredness and exercise enduranceNot enough evidence
Heart attack, stroke and homocysteineMixed findings
'Methylated' folate versus folic acid: blood folateLow certainty
A methylated B blend in people with certain gene variantsLow certainty
B12 forms: methylcobalamin versus cyanocobalaminNot enough evidence
L-methylfolate added to antidepressantsLow certainty
Nerve symptoms (neuropathy)Low certainty
Folic acid before and during pregnancyLow certainty

Lab markers tracked in the studies

Perceived Stress ScaleBlood lactate and ammonia during exerciseHomocysteineRed blood cell folate

What is B-Complex Formulas good for?

What research on B vitamins found, by use, and how strong it is. Most trials tested single B vitamins or mixed products that differ from the one you may be holding, so a result for one product does not carry over to another. Several trials were small or linked to makers.

Stress and moodLow certaintyA 2019 pooled review of 16 trials (2,015 people) of products with three or more B vitamins found a small gain on stress, no clear gain on depression and no gain on anxiety. One trial of 215 working men on a high-dose B-complex with vitamin C and minerals found better stress ratings after 33 days. Products and groups differed a lot, so this is low-certainty. Thinking skills and memoryEvidence againstReviews of randomised trials found no benefit from B12 alone or from B complex on thinking skills in people without B12 deficiency or advanced brain disease. A Cochrane review found B vitamins given to healthy adults in their 60s and 70s probably have little or no effect on overall thinking function. Energy, tiredness and exercise enduranceNot enough evidenceB vitamins help the body release energy from food, but that does not show that extra amounts raise energy when intake is already enough. One small 28-day trial of 32 healthy young adults using a B1, B2, B6 and B12 tablet reported longer running time to exhaustion and lower lactate and ammonia. A review found only one trial that measured everyday tiredness, so it could not judge it. Heart attack, stroke and homocysteineMixed findingsFolic acid, B6 and B12 lower homocysteine, a blood marker linked to heart disease. But a 2017 Cochrane review of 15 trials (71,422 people) found no difference in heart attack or death from any cause. Stroke was slightly lower (RR 0.90). A 2010 pooled analysis of 8 folic acid trials found no effect on vascular events, cancer or death. 'Methylated' folate versus folic acid: blood folateLow certaintyIn a 24-week trial of 144 women, the methyl form of folate raised red blood cell folate more than an equal amount of folic acid. A review says the two forms act alike at equal molar amounts. No trial in the sources read compared health outcomes such as birth defects. A methylated B blend in people with certain gene variantsLow certaintyOne 6-month trial of 54 adults with raised homocysteine and MTHFR, MTR or MTRR gene variants found that methylfolate, active B6 and methylcobalamin lowered homocysteine by 30% and LDL cholesterol by 7.5% more than placebo. It was small, run by authors employed by the product company, and had no comparison with plain folic acid. B12 forms: methylcobalamin versus cyanocobalaminNot enough evidenceLabels often say methylcobalamin is better than cyanocobalamin. The review read compares the forms but its abstract states no head-to-head result. No trial comparing health outcomes was read. L-methylfolate added to antidepressantsLow certaintyA 2022 review found that L-methylfolate added to an antidepressant gave a small extra effect in adults with major depression who were already on medicine. This is one folate form given with a prescription, not a B-complex, and not a treatment for people who are not on an antidepressant. Nerve symptoms (neuropathy)Low certaintyPeople with nerve damage (peripheral neuropathy) tend to have lower B12 and higher markers of low B12. In treatment trials, B12 showed a non-significant link to symptom improvement and B1 a link to improvement; seven trials combined were also non-significant. For B6, high amounts cause nerve damage and a treatment role could not be confirmed. Folic acid before and during pregnancyLow certaintyThe NHS recommends a 400 microgram folic acid supplement for anyone pregnant or who could become pregnant, to help prevent neural tube defects such as spina bifida. A 2023 evidence review of observational studies for a US task force found fewer neural tube defects with folic acid in one cohort, no significant harms, and results consistent with earlier evidence.

Benefits, one by one

Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.

Stress and mood

Low certainty

A 2019 pooled review of 16 trials (2,015 people) of products with three or more B vitamins found a small gain on stress, no clear gain on depression and no gain on anxiety. One trial of 215 working men on a high-dose B-complex with vitamin C and minerals found better stress ratings after 33 days. Products and groups differed a lot, so this is low-certainty.

2 studiesProducts differ. The forms and amounts tested are in the studies tabl…

Studies, doses and limits

What the trials found

The 2019 review pooled trials that gave three or more B vitamins for at least four weeks. Eleven of 18 articles reported better overall mood or a mood facet than placebo. The stress result pooled 958 people (SMD 0.23); depression pooled 568 people (SMD 0.15, not significant, p = 0.07); anxiety pooled 562 people (SMD 0.03, no effect). In the 215-man trial, ratings of stress (PSS), general health (GHQ-12) and the 'vigour' mood scale improved with the product. That product also held vitamin C and minerals.

Results

Low-certainty small benefit for stress ratings. No clear benefit for depression or anxiety.

Effect sizes as reported

Stress SMD 0.23 (95% CI 0.02 to 0.45); depressive symptoms SMD 0.15 (-0.01 to 0.32); anxiety SMD 0.03 (-0.13 to 0.20).

Why this rating

Low because the stress effect is small with a range of uncertainty that nearly includes zero, products and people vary, and authors of the pooled review report industry funding. The single trial was one branded product with other ingredients.

Form and dose studied

Products differ. The forms and amounts tested are in the studies table, not a suggestion.

Who was studied

Healthy adults and 'at-risk' groups (poor nutrient or mood status); the single trial was in working men aged 30 to 55.

Limits

Self-rated scores. Mixed products mean the trials cannot say which vitamin did what. Short trials (4 weeks or more; one of 33 days).

Why researchers looked

People often take B vitamins hoping to feel less stressed or low, so researchers tested whether a mix of B vitamins changes mood scores.

Traditional use

B-complex products bundle several of the eight B vitamins in one tablet, capsule or gummy. Which vitamins, in what forms and amounts, differs by product.

Proposed mechanism Not established

Not established. The B vitamins have known roles in how the body handles food energy and nerve function, but the trials read do not show how a mood effect would work.

A proposed mechanism does not show that the effect happens in people.

No safety problem was noted in the abstracts read. See the Safety tab for B6, niacin and folic acid cautions.

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Thinking skills and memory

Evidence against

Reviews of randomised trials found no benefit from B12 alone or from B complex on thinking skills in people without B12 deficiency or advanced brain disease. A Cochrane review found B vitamins given to healthy adults in their 60s and 70s probably have little or no effect on overall thinking function.

2 studiesProducts differ. The forms and amounts tested are in the studies tabl…

Studies, doses and limits

What the trials found

Markun 2021 pooled 16 trials (6,276 people) and found no effect of B12 alone or B complex on any thinking skill and no overall effect on depression measures. The 2018 Cochrane review included 14 trials (27,882 people) of folic acid, B12 or B6; most people were over 60 and many had heart or vessel disease. Effects on global thinking were near zero up to 5 years (SMD -0.03 to 0.06) and at 5 to 10 years (SMD -0.01). Three trials of combined B-vitamin, antioxidant and mineral products (6,306 people) also found little or no effect.

Results

Evidence against a benefit in people without deficiency. Moderate or low certainty of little or no effect.

Effect sizes as reported

B vitamins up to 5 years: SMD -0.03 to 0.06; 5 to 10 years: SMD -0.01. Complex supplements: mean difference 0.12 TICS points (-0.14 to 0.38).

Why this rating

Two independent reviews agree on no benefit. The Cochrane authors rate most results as moderate or low certainty and say the evidence does not allow definitive conclusions.

Form and dose studied

Products differ. The forms and amounts tested are in the studies table, not a suggestion.

Who was studied

Cognitively healthy adults, mostly aged 60 and over, often with heart or vessel disease; people without advanced brain disease or overt B12 deficiency.

Limits

Most trials were not designed to test thinking skills, used brief tests, and few included people younger than 60. Trials in people who are actually deficient are a different question.

Why researchers looked

B12, B6 and folate are linked to brain health and to homocysteine, so many trials asked whether supplements protect memory.

Traditional use

B-complex products bundle several of the eight B vitamins in one tablet, capsule or gummy. Which vitamins, in what forms and amounts, differs by product.

Proposed mechanism Not established

Not established. Homocysteine was the proposed link, but lowering it did not change thinking scores in these trials.

A proposed mechanism does not show that the effect happens in people.

Very sparse data on side effects in these reviews.

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Energy, tiredness and exercise endurance

Not enough evidence

B vitamins help the body release energy from food, but that does not show that extra amounts raise energy when intake is already enough. One small 28-day trial of 32 healthy young adults using a B1, B2, B6 and B12 tablet reported longer running time to exhaustion and lower lactate and ammonia. A review found only one trial that measured everyday tiredness, so it could not judge it.

4 studiesProducts differ. The forms and amounts tested are in the studies tabl…

Studies, doses and limits

What the trials found

The 28-day crossover trial in 32 healthy adults aged 20 to 30 reported a 1.26-fold longer running time to exhaustion than before and than placebo, and lower blood lactate and ammonia during and after exercise. The 215-man trial found men rated themselves less mentally tired on a thinking battery. The B12 and B-complex review (Markun 2021) found only one trial of unexplained fatigue, so no analysis was possible.

Results

Insufficient evidence. One very small trial gives a promising treadmill result; everyday tiredness is not tested.

Effect sizes as reported

Running time to exhaustion 1.26-fold (p < 0.05); lower lactate and ammonia (p < 0.05).

Why this rating

Insufficient: one very small trial with an unclear design, no repeat by other groups, and no pooled evidence on everyday tiredness.

Form and dose studied

Products differ. The forms and amounts tested are in the studies table, not a suggestion.

Who was studied

Healthy young adults (the exercise trial); working men aged 30 to 55 (the mood trial).

Limits

Small sample, short time, treadmill and blood tests rather than daily energy. A person who is deficient in a B vitamin is a different case from these healthy volunteers.

Why researchers looked

Energy and tiredness are the most common reasons printed on B-complex labels.

Traditional use

B-complex products bundle several of the eight B vitamins in one tablet, capsule or gummy. Which vitamins, in what forms and amounts, differs by product.

Proposed mechanism Authoritative guidance

The NHS says thiamin, riboflavin, niacin, pantothenic acid and B12 help release energy from food. That is a normal-role statement, not a test of a boost from extra amounts.

A proposed mechanism does not show that the effect happens in people.

The exercise trial reported no side effects.

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Heart attack, stroke and homocysteine

Mixed findings

Folic acid, B6 and B12 lower homocysteine, a blood marker linked to heart disease. But a 2017 Cochrane review of 15 trials (71,422 people) found no difference in heart attack or death from any cause. Stroke was slightly lower (RR 0.90). A 2010 pooled analysis of 8 folic acid trials found no effect on vascular events, cancer or death.

2 studiesTrials used B6, folate and B12 alone or in pairs and triples; they we…

Studies, doses and limits

What the trials found

Cochrane 2017: heart attack RR 1.02 (0.95 to 1.10); death from any cause RR 1.01 (0.96 to 1.06); serious adverse events RR 1.07 (1.00 to 1.14); stroke RR 0.90 (0.82 to 0.99, 10 trials, 44,224 people). Clarke 2010 (8 trials, 37,485 people at raised heart risk): folic acid lowered homocysteine about 25%; major vascular events RR 1.01 (0.97 to 1.05), stroke RR 0.96 (0.87 to 1.06), cancer RR 1.05 (0.98 to 1.13), death RR 1.02 (0.97 to 1.08).

Results

Mixed. High-quality evidence of no effect on heart attack or death; a small stroke signal at the edge of chance in one review and none in the other.

Effect sizes as reported

Stroke RR 0.90 (0.82 to 0.99) in Cochrane 2017; RR 0.96 (0.87 to 1.06) in Clarke 2010.

Why this rating

Mixed because the two reviews disagree slightly on stroke. The Cochrane authors rate the heart attack and death findings as high-quality evidence of no difference.

Form and dose studied

Trials used B6, folate and B12 alone or in pairs and triples; they were not tests of finished B-complex products. Amounts are in the studies table.

Who was studied

People with or at high risk of heart or blood-vessel disease, mostly older adults.

Limits

These are not trials of healthy people or of B-complex products. The stroke difference is small and sits near chance.

Why researchers looked

High homocysteine is linked to heart disease, so researchers tested whether lowering it with B vitamins prevents heart attacks and strokes.

Traditional use

B-complex products bundle several of the eight B vitamins in one tablet, capsule or gummy. Which vitamins, in what forms and amounts, differs by product.

Proposed mechanism Review statement

Homocysteine is an amino acid in methionine handling (Cochrane). Lowering it was the proposed route; trial results show it lowers homocysteine but does not reduce heart attacks.

A proposed mechanism does not show that the effect happens in people.

No increase in cancer was found in either review.

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'Methylated' folate versus folic acid: blood folate

Low certainty

In a 24-week trial of 144 women, the methyl form of folate raised red blood cell folate more than an equal amount of folic acid. A review says the two forms act alike at equal molar amounts. No trial in the sources read compared health outcomes such as birth defects.

4 studiesThe methyl form (5-MTHF) and folic acid, compared in equal molar amou…

Studies, doses and limits

What the trials found

Lamers 2006: in 144 healthy women aged 19 to 33, red blood cell folate rose more over 24 weeks with 416 micrograms of the methyl form than with 400 micrograms of folic acid or 208 micrograms of the methyl form (P < 0.001). Pietrzik 2010 (narrative review): the forms have comparable activity and availability at equal molar amounts; possible advantages for the methyl form are suggested but not shown by outcome trials. Mazokopakis 2023 (272 adults): L-methylfolate and folinic acid lowered homocysteine equally over three months.

Results

Low-certainty for blood folate (one trial plus a review); insufficient for any health outcome.

Effect sizes as reported

Red blood cell folate rise greater with equimolar methyl form than folic acid (P < 0.001).

Why this rating

Low: one randomised trial of a blood marker, plus a narrative review. Insufficient evidence for any health outcome because none was measured.

Form and dose studied

The methyl form (5-MTHF) and folic acid, compared in equal molar amounts. Amounts are in the studies table.

Who was studied

Healthy women aged 19 to 33 (Lamers); healthy Greek adults with homocysteine of 10 or more (Mazokopakis).

Limits

Blood markers only. The finding is about folate and does not carry over to other 'methylated' B vitamins.

Why researchers looked

Labels often say 'methylated' or 'active' folate and imply it is better than folic acid, so researchers compared the blood response to each.

Traditional use

B-complex products bundle several of the eight B vitamins in one tablet, capsule or gummy. Which vitamins, in what forms and amounts, differs by product.

Proposed mechanism Established physiology

Folic acid is a synthetic form that must be converted in the body. L-5-methyl-THF is the main natural form in food and the form found in blood (Pietrzik review).

A proposed mechanism does not show that the effect happens in people.

No safety problem noted in the abstracts. The NHS advice for pregnancy is a folic acid supplement; ask a clinician about forms.

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A methylated B blend in people with certain gene variants

Low certainty

One 6-month trial of 54 adults with raised homocysteine and MTHFR, MTR or MTRR gene variants found that methylfolate, active B6 and methylcobalamin lowered homocysteine by 30% and LDL cholesterol by 7.5% more than placebo. It was small, run by authors employed by the product company, and had no comparison with plain folic acid.

1 studiesMethylfolate with the active form of B6 and methylcobalamin, one bran…

Studies, doses and limits

What the trials found

Over six months the blend group had homocysteine 30.0% lower (95% CI -39.7% to -20.3%) and LDL cholesterol 7.5% lower (-10.3% to -4.7%) than placebo. Homocysteine fell more in people with two copies of the minor variants (48.3%) than in mixed carriers (18.6%).

Results

Low-certainty marker changes in a very small, company-linked trial. No outcome data.

Effect sizes as reported

Homocysteine -30.0%; LDL cholesterol -7.5% versus placebo.

Why this rating

Low: 54 people, a selected genetic profile, authors employed by the maker, no plain-vitamin comparison and no heart outcomes.

Form and dose studied

Methylfolate with the active form of B6 and methylcobalamin, one branded blend; amounts are in the studies table.

Who was studied

Adults aged 40 to 75 with raised homocysteine, moderate LDL and gene variants.

Limits

Cannot show that methylated forms beat ordinary forms or that people without these variants gain. Blood markers only.

Why researchers looked

Marketing often links 'methylated' vitamins to common gene variants such as MTHFR, so a trial tested one blend in people carrying such variants.

Traditional use

B-complex products bundle several of the eight B vitamins in one tablet, capsule or gummy. Which vitamins, in what forms and amounts, differs by product.

Proposed mechanism Author hypothesis

Not established. The authors link the genes to how the body handles homocysteine; no mechanism was tested in the trial.

A proposed mechanism does not show that the effect happens in people.

No safety findings in the abstract.

¹⁷

B12 forms: methylcobalamin versus cyanocobalamin

Not enough evidence

Labels often say methylcobalamin is better than cyanocobalamin. The review read compares the forms but its abstract states no head-to-head result. No trial comparing health outcomes was read.

1 studiesMethylcobalamin, adenosylcobalamin and cyanocobalamin.

Studies, doses and limits

What the trials found

A 2025 narrative review says supplements raise blood B12 to a similar extent as diet in healthy people, and are required in conditions such as megaloblastic anaemia. It compares the forms in common scenarios, but the abstract states no result favouring either form.

Results

Insufficient evidence for a difference between B12 forms.

Effect sizes as reported

No numbers in the abstract.

Why this rating

Insufficient: one narrative review whose abstract gives no comparison result, and no trial found for health outcomes.

Form and dose studied

Methylcobalamin, adenosylcobalamin and cyanocobalamin.

Who was studied

Healthy people and people with deficiency, as described in the review.

Limits

Only the abstract was read, so the review's detailed comparisons are not reported here.

Why researchers looked

People ask whether the 'natural' B12 form works better than the common synthetic form.

Traditional use

B-complex products bundle several of the eight B vitamins in one tablet, capsule or gummy. Which vitamins, in what forms and amounts, differs by product.

Proposed mechanism Not established

Not established. The review describes the natural forms (methylcobalamin, adenosylcobalamin) and the synthetic form (cyanocobalamin) but its abstract gives no mechanism finding.

A proposed mechanism does not show that the effect happens in people.

No safety comparison read.

L-methylfolate added to antidepressants

Low certainty

A 2022 review found that L-methylfolate added to an antidepressant gave a small extra effect in adults with major depression who were already on medicine. This is one folate form given with a prescription, not a B-complex, and not a treatment for people who are not on an antidepressant.

1 studiesL-methylfolate alone, added to an antidepressant; amounts are not sta…

Studies, doses and limits

What the trials found

Nine articles (6,707 patients) suggested better antidepressant response. Pooled: response RR 1.25 (1.08 to 1.46; 3 studies, 483 people); depression score SMD -0.38 (-0.59 to -0.17; 4 studies, 507 people).

Results

Low-certainty small extra effect as an add-on to antidepressants.

Effect sizes as reported

Response RR 1.25; depression score SMD -0.38.

Why this rating

Low: few small studies, people already on medicine, and authors with links to a genetic-testing company.

Form and dose studied

L-methylfolate alone, added to an antidepressant; amounts are not stated in the abstract.

Who was studied

Adults with major depression taking antidepressants.

Limits

Should not be read as support for B-complex products for depression. Decisions on depression treatment belong with a clinician.

Why researchers looked

L-methylfolate is a prescription-type add-on studied in people whose antidepressant only partly worked.

Traditional use

B-complex products bundle several of the eight B vitamins in one tablet, capsule or gummy. Which vitamins, in what forms and amounts, differs by product.

Proposed mechanism Not established

Not established in the abstract.

A proposed mechanism does not show that the effect happens in people.

Not described in the abstract.

¹²

Nerve symptoms (neuropathy)

Low certainty

People with nerve damage (peripheral neuropathy) tend to have lower B12 and higher markers of low B12. In treatment trials, B12 showed a non-significant link to symptom improvement and B1 a link to improvement; seven trials combined were also non-significant. For B6, high amounts cause nerve damage and a treatment role could not be confirmed.

1 studiesB12, B1 and others as treatment, often in combination; amounts are in…

Studies, doses and limits

What the trials found

Stein 2021: nerve damage was linked to lower B12 (OR 1.51, 1.23 to 1.84), higher methylmalonic acid (2.53, 1.39 to 4.60) and higher homocysteine (3.48, 2.01 to 6.04). Treatment: B12 OR 1.36 (0.66 to 2.79, 4 studies); B1 OR 5.34 (1.87 to 15.19, 3 studies, p = 0.059); all 7 trials OR 2.58 (0.98 to 6.79). Muhamad 2023: no firm evidence that low B6 causes neuropathy; no B6-alone treatment data.

Results

Low-certainty, mixed. Association with low B12 is clear; treatment benefit is not shown.

Effect sizes as reported

B12 treatment OR 1.36 (0.66 to 2.79); all trials OR 2.58 (0.98 to 6.79).

Why this rating

Low: few and mixed-quality trials that mostly did not check vitamin status before treatment and varied widely in results.

Form and dose studied

B12, B1 and others as treatment, often in combination; amounts are in the studies table.

Who was studied

People with peripheral neuropathy, many with diabetes.

Limits

The meta-analysis calls for well-designed trials, especially in neuropathy not caused by diabetes. Too much B6 can itself damage nerves (see Safety).

Why researchers looked

Numbness, tingling and burning in the hands and feet often have a B-vitamin link, so B vitamins have been tested as treatment.

Traditional use

B-complex products bundle several of the eight B vitamins in one tablet, capsule or gummy. Which vitamins, in what forms and amounts, differs by product.

Proposed mechanism Human biomarker

Not established. Low B12 raises methylmalonic acid and homocysteine, which are markers of B12 shortage.

A proposed mechanism does not show that the effect happens in people.

High B6 can cause the problem it is sometimes used for.

¹⁹

Folic acid before and during pregnancy

Low certainty

The NHS recommends a 400 microgram folic acid supplement for anyone pregnant or who could become pregnant, to help prevent neural tube defects such as spina bifida. A 2023 evidence review of observational studies for a US task force found fewer neural tube defects with folic acid in one cohort, no significant harms, and results consistent with earlier evidence.

2 studiesFolic acid. The NHS advice is a specific supplement; higher amounts f…

Studies, doses and limits

What the trials found

The 2023 review included 12 observational studies (1,244,072 people); 3 (990,372) looked at neural tube defects. One cohort found adjusted relative risks of 0.54 (before pregnancy), 0.62 (during) and 0.49 (both) but only in the later of two time periods. No harms for twins, autism or maternal cancer were significant.

Results

Low-certainty from the studies read here (observational); supported by the NHS recommendation.

Effect sizes as reported

aRR 0.49 to 0.62 depending on timing, in one cohort.

Why this rating

Low in the data read here because the update covers observational studies only; earlier evidence it refers to was not read.

Form and dose studied

Folic acid. The NHS advice is a specific supplement; higher amounts for some women only on a doctor's advice.

Who was studied

Women of childbearing age and pregnant women in highly developed countries.

Limits

A B-complex tablet may not contain the amount or form the NHS advice describes; that is a question for a clinician or pharmacist.

Why researchers looked

Folic acid is a B vitamin with a long-established public-health role before and in early pregnancy. This is a single-vitamin finding, not a test of B-complex products.

Traditional use

B-complex products bundle several of the eight B vitamins in one tablet, capsule or gummy. Which vitamins, in what forms and amounts, differs by product.

Proposed mechanism Authoritative guidance

Folate helps the body form healthy red blood cells and reduces the risk of neural tube defects (NHS statement).

A proposed mechanism does not show that the effect happens in people.

See Safety for folic acid and B12 masking.

^{20 27}

Connections to the rest of health

How B-Complex Formulas connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.

Explore every connection: goals, body systems, organs, symptoms, genes

Kind of connection Connected to Search

A. Wellness goals

Connected to	Evidence status	Context	Studies
Stress Reduction	Low certainty	Stress and mood: A 2019 pooled review of 16 trials (2,015 people) of products with three or more B vitamins found a small gain on stress, no clear gain on depression and no gain on anxiety. One trial of 215 working men on a high-dose B-complex with vitamin C and minerals found better stress ratings after 33 days. Products and groups differed a lot, so this is low-certainty.	^{22 6}
Mood Balance	Low certainty	Stress and mood: A 2019 pooled review of 16 trials (2,015 people) of products with three or more B vitamins found a small gain on stress, no clear gain on depression and no gain on anxiety. One trial of 215 working men on a high-dose B-complex with vitamin C and minerals found better stress ratings after 33 days. Products and groups differed a lot, so this is low-certainty.	^{22 6}
Memory Support	Evidence against	Thinking skills and memory: Reviews of randomised trials found no benefit from B12 alone or from B complex on thinking skills in people without B12 deficiency or advanced brain disease. A Cochrane review found B vitamins given to healthy adults in their 60s and 70s probably have little or no effect on overall thinking function.	^{10 18}
Brain Health	Evidence against	Thinking skills and memory: Reviews of randomised trials found no benefit from B12 alone or from B complex on thinking skills in people without B12 deficiency or advanced brain disease. A Cochrane review found B vitamins given to healthy adults in their 60s and 70s probably have little or no effect on overall thinking function.	^{10 18}
Energy Boost	Not enough evidence	Energy, tiredness and exercise endurance: B vitamins help the body release energy from food, but that does not show that extra amounts raise energy when intake is already enough. One small 28-day trial of 32 healthy young adults using a B1, B2, B6 and B12 tablet reported longer running time to exhaustion and lower lactate and ammonia. A review found only one trial that measured everyday tiredness, so it could not judge it.	^{8 6 10 27}
Reduce Fatigue	Not enough evidence	Energy, tiredness and exercise endurance: B vitamins help the body release energy from food, but that does not show that extra amounts raise energy when intake is already enough. One small 28-day trial of 32 healthy young adults using a B1, B2, B6 and B12 tablet reported longer running time to exhaustion and lower lactate and ammonia. A review found only one trial that measured everyday tiredness, so it could not judge it.	^{8 6 10 27}
Heart Health	Mixed findings	Heart attack, stroke and homocysteine: Folic acid, B6 and B12 lower homocysteine, a blood marker linked to heart disease. But a 2017 Cochrane review of 15 trials (71,422 people) found no difference in heart attack or death from any cause. Stroke was slightly lower (RR 0.90). A 2010 pooled analysis of 8 folic acid trials found no effect on vascular events, cancer or death.	^{11 4}
Cholesterol Balance	Mixed findings	Heart attack, stroke and homocysteine: Folic acid, B6 and B12 lower homocysteine, a blood marker linked to heart disease. But a 2017 Cochrane review of 15 trials (71,422 people) found no difference in heart attack or death from any cause. Stroke was slightly lower (RR 0.90). A 2010 pooled analysis of 8 folic acid trials found no effect on vascular events, cancer or death.	^{11 4}
Balanced Nutrition	Low certainty	'Methylated' folate versus folic acid: blood folate: In a 24-week trial of 144 women, the methyl form of folate raised red blood cell folate more than an equal amount of folic acid. A review says the two forms act alike at equal molar amounts. No trial in the sources read compared health outcomes such as birth defects.	^{7 16 13 27}
Womens Wellness	Low certainty	'Methylated' folate versus folic acid: blood folate: In a 24-week trial of 144 women, the methyl form of folate raised red blood cell folate more than an equal amount of folic acid. A review says the two forms act alike at equal molar amounts. No trial in the sources read compared health outcomes such as birth defects.	^{7 16 13 27}
Heart Health	Low certainty	A methylated B blend in people with certain gene variants: One 6-month trial of 54 adults with raised homocysteine and MTHFR, MTR or MTRR gene variants found that methylfolate, active B6 and methylcobalamin lowered homocysteine by 30% and LDL cholesterol by 7.5% more than placebo. It was small, run by authors employed by the product company, and had no comparison with plain folic acid.	¹⁷
Cholesterol Balance	Low certainty	A methylated B blend in people with certain gene variants: One 6-month trial of 54 adults with raised homocysteine and MTHFR, MTR or MTRR gene variants found that methylfolate, active B6 and methylcobalamin lowered homocysteine by 30% and LDL cholesterol by 7.5% more than placebo. It was small, run by authors employed by the product company, and had no comparison with plain folic acid.	¹⁷
Balanced Nutrition	Not enough evidence	B12 forms: methylcobalamin versus cyanocobalamin: Labels often say methylcobalamin is better than cyanocobalamin. The review read compares the forms but its abstract states no head-to-head result. No trial comparing health outcomes was read.	²
Mood Balance	Low certainty	L-methylfolate added to antidepressants: A 2022 review found that L-methylfolate added to an antidepressant gave a small extra effect in adults with major depression who were already on medicine. This is one folate form given with a prescription, not a B-complex, and not a treatment for people who are not on an antidepressant.	¹²
Healthy Aging	Low certainty	Nerve symptoms (neuropathy): People with nerve damage (peripheral neuropathy) tend to have lower B12 and higher markers of low B12. In treatment trials, B12 showed a non-significant link to symptom improvement and B1 a link to improvement; seven trials combined were also non-significant. For B6, high amounts cause nerve damage and a treatment role could not be confirmed.	¹⁹
Womens Wellness	Low certainty	Folic acid before and during pregnancy: The NHS recommends a 400 microgram folic acid supplement for anyone pregnant or who could become pregnant, to help prevent neural tube defects such as spina bifida. A 2023 evidence review of observational studies for a US task force found fewer neural tube defects with folic acid in one cohort, no significant harms, and results consistent with earlier evidence.	^{20 27}
Preventive Wellness	Low certainty	Folic acid before and during pregnancy: The NHS recommends a 400 microgram folic acid supplement for anyone pregnant or who could become pregnant, to help prevent neural tube defects such as spina bifida. A 2023 evidence review of observational studies for a US task force found fewer neural tube defects with folic acid in one cohort, no significant harms, and results consistent with earlier evidence.	^{20 27}

B. Body systems

Connected to	Kind of connection	Evidence status	Context	Studies
Nervous System	Biological association	Low certainty	Studied for: Stress and mood Studied for: Thinking skills and memory	^{22 6 10 18 12 19 20 27}
Stress Mood	Biological association	Low certainty	Studied for: Stress and mood Studied for: L-methylfolate added to antidepressants	^{22 6 12}
Brain Focus	Biological association	Evidence against	Studied for: Thinking skills and memory	^{10 18}
Energy Fatigue	Biological association	Not enough evidence	Studied for: Energy, tiredness and exercise endurance	^{8 6 10 27}
Metabolism	Biological association	Not enough evidence	Studied for: Energy, tiredness and exercise endurance	^{8 6 10 27}
Cardiovascular System	Biological association	Mixed findings	Studied for: Heart attack, stroke and homocysteine Studied for: A methylated B blend in people with certain gene variants	^{11 4 17}
Heart Circulation	Biological association	Mixed findings	Studied for: Heart attack, stroke and homocysteine	^{11 4}
Nutrition	Biological association	Low certainty	Studied for: 'Methylated' folate versus folic acid: blood folate Studied for: B12 forms: methylcobalamin versus cyanocobalamin	^{7 16 13 27 2}
Reproductive System	Biological association	Low certainty	Studied for: 'Methylated' folate versus folic acid: blood folate Studied for: Folic acid before and during pregnancy	^{7 16 13 27 20}
Blood	Biological association	Low certainty	Studied for: A methylated B blend in people with certain gene variants Studied for: B12 forms: methylcobalamin versus cyanocobalamin	^{17 2}

I. Biomarkers

Connected to	Kind of connection	Evidence status	Context	Studies
Homocysteine		Preliminary	B vitamins lowered homocysteine but did not reduce heart attacks. Preparation or compound: B6, folate, B12	^{11 4}
Perceived Stress Scale	Biological association	Low certainty	Measured in trials: lower stress ratings. A lab change is not the same as a health benefit.	^{6 22}
Blood lactate and ammonia during exercise	Biological association	Not enough evidence	Measured in trials: lower during and after exercise. A lab change is not the same as a health benefit.	⁸
Homocysteine	Biological association	Moderate certainty	Measured in trials: lower with folate, B6, B12. A lab change is not the same as a health benefit.	^{4 17 13 11}
Red blood cell folate	Biological association	Low certainty	Measured in trials: higher. A lab change is not the same as a health benefit.	⁷

J. Genes, receptors and enzymes

Connected to	Kind of connection	Evidence status	Context	Studies
MTHFR	Preliminary mechanism	Human	A gene involved in folate handling. Variants were used to select people in a 2024 trial of a methylated blend and affected homocysteine response in a 2023 trial.	^{17 13}
MTR and MTRR	Preliminary mechanism	Human	Genes in B12-dependent homocysteine handling, named in the 2024 trial.	¹⁷

K. Biological pathways

Connected to	Kind of connection	Evidence status	Context	Studies
Homocysteine	Preliminary mechanism	Human	Lowered by folate, B6 and B12; lowering it did not prevent heart attacks in the Cochrane review.	^{11 4}
Vitamin B12 and folate	Preliminary mechanism	Human	Folic acid can hide B12 deficiency (NHS).	^{27 14}

L. Active compounds

Connected to	Kind of connection	Evidence status	Context	Studies
Thiamin (vitamin B1)	Biological association	Human	NHS: helps the body break down and release energy from food and keeps the nervous system healthy. Food sources named: peas, some fruits, nuts, wholegrain bread, fortified cereals, liver.	²⁷
Riboflavin (vitamin B2)	Biological association	Human	NHS: keeps skin, eyes and the nervous system healthy and helps release energy from food. Food sources named: milk, eggs, fortified cereals, mushrooms, plain yoghurt.	²⁷
Niacin (vitamin B3): nicotinic acid and nicotinamide	Biological association	Human	NHS: helps release energy from food and keeps the nervous system and skin healthy. Nicotinic acid can cause flushing; nicotinamide does not appear to (MedlinePlus). Food sources named: meat, fish, wheat flour, eggs.	^{27 26}
Pantothenic acid (vitamin B5)	Biological association	Human	NHS: helps release energy from food. Food sources named: chicken, beef, liver and kidneys, eggs, mushrooms, avocado.	²⁷
Vitamin B6 (pyridoxine; active form pyridoxal-5'-phosphate)	Biological association	Human	NHS: helps the body use and store energy from protein and carbohydrate and form haemoglobin. Food sources named: pork, poultry, some fish, peanuts, soya beans, wheatgerm, oats, bananas, milk.	^{27 15}
Biotin (vitamin B7)	Biological association	Human	NHS: needed in very small amounts to help the body make fatty acids; found in a wide range of foods at very low levels. High doses can disturb some blood tests.	^{27 9}
Folate, folic acid and methylfolate (5-MTHF)	Biological association	Human	NHS: folate helps form red blood cells and lowers the risk of neural tube defects; folic acid is the manmade form. Pietrzik review: folic acid is synthetic and must be converted in cells; L-5-methyl-THF is the main natural form and the form found in blood. Food sources named: broccoli, Brussels sprouts, leafy greens, peas, chickpeas and kidney beans, liver, fortified cereals.	^{27 16}
Vitamin B12 (cyanocobalamin, methylcobalamin, adenosylcobalamin)	Biological association	Human	NHS: helps make red blood cells, keeps the nervous system healthy, releases energy from food and helps the body use folate. Food sources named: meat, fish, milk, cheese, eggs, fortified cereals; the NHS says vegans may not get enough.	^{27 2}

Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 26, 2026).

Evidence at a glance: what the research found for 10 outcomes

6Low certainty

1Mixed findings

2Not enough evidence

1Evidence against

Each outcome below is one thing researchers measured. Certainty is how far the evidence can be trusted, not how well it works. The full studies are on the next tab.

Stress and mood 2 studies Low certainty Thinking skills and memory 2 studies Evidence against Energy, tiredness and exercise endurance 4 studies Not enough evidence Heart attack, stroke and homocysteine 2 studies Mixed findings 'Methylated' folate versus folic acid: blood folate 4 studies Low certainty A methylated B blend in people with certain gene variants 1 study Low certainty B12 forms: methylcobalamin versus cyanocobalamin 1 study Not enough evidence L-methylfolate added to antidepressants 1 study Low certainty Nerve symptoms (neuropathy) 1 study Low certainty Folic acid before and during pregnancy 2 studies Low certainty

The evidence

The research centre for B-Complex Formulas. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.

Evidence by outcome

Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).

How we rate evidence

High certainty

Several well-run trials or reviews agree; further research is unlikely to change the picture much.

Moderate certainty

Good trials point the same way, but some doubt remains.

Low certainty

Small, short or inconsistent trials. The finding could change with better research.

Very low certainty

Very little or very weak human data. Treat as a possibility only.

Mixed findings

Trials or reviews disagree with each other.

Not enough evidence

Not enough human research to say either way.

Evidence against

Good research found no benefit, or found harm.

We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We re-read PubMed abstracts for every review, trial and laboratory study cited, after checking titles. Only abstracts were read for studies. The NHS, MedlinePlus and FDA pages were read in full. NIH ODS and EFSA pages were blocked, and the FDA biotin communication was not found, so they are marked unverified and nothing is stated from them.

Study library: every study we checked 28

Design Research type Year from Search

Study	Design	People	Product, dose, length	Result
Andrews 2018 Dietary Supplement Ingredient Database (DSID) and the Application of Analytically Based Estimates of Ingredient Amount to Intake Calculations. J Nutr · PMID 31505677 · DOI	Laboratory analysis	US government laboratory data on multivitamin-mineral products and others sold in the US	Multivitamin-mineral products (chemical analysis versus label) Oral · vs Label amounts	Makers often add more than the label says, and the extra is not standardised. For several nutrients, predicted amounts more than 20% above the label are expected in 50% to 99% of multivitamin-mineral products (for example iodine and selenium in adult products). Folic acid is predicted to be more than 10% above label in the vast majority of adult and children's multivitamin-mineral products. Folic acid overage above 10% in most adult and children's products (Not applicable) Methods, limits and funding Outcomes: Actual versus labelled ingredient amounts Limitations: About multivitamin-mineral products in general, not B-complex products specifically. B-vitamin results other than folic acid were not given in the abstract. Funding and conflicts: Crown copyright; government authors with academic co-authors. No conflict statement in the record read. Read: abstract
Behringer 2025 Vitamin B12: A Comprehensive Review of Natural vs Synthetic Forms of Consumption and Supplementation. Cureus · PMID 41362547 · DOI	Narrative review	Narrative review of B12 physiology, deficiency and supplement forms	Methylcobalamin, adenosylcobalamin (natural forms) and cyanocobalamin (the widely used synthetic form) Oral	The abstract says that in healthy people supplements raise blood B12 to a similar extent as diet, that supplements are needed in conditions like megaloblastic anaemia, and that it compares the forms, but it states no head-to-head result. No head-to-head result in the abstract (Not applicable) Methods, limits and funding Outcomes: Absorption, metabolism, clinical effect of B12 forms Limitations: A narrative review. The abstract gives no finding on whether one B12 form works better. Only the abstract was read. Funding and conflicts: Authors declare no funding and no conflicts. Read: abstract
Brasky 2017 Long-Term, Supplemental, One-Carbon Metabolism-Related Vitamin B Use in Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort. J Clin Oncol · PMID 28829668 · DOI	Cohort observational	77118 77,118 adults aged 50 to 76 followed for lung cancer (808 cases)	Supplemental vitamins B6, folate and B12, from individual supplements and from multivitamins Oral 10-year average daily amounts from the questionnaire 10-year average use · vs Non-users	In women there was no link. In men, vitamin B6 and B12 from individual supplements (not from multivitamins) was linked with 30% to 40% more lung cancer. At the highest average amounts (B6 above 20 mg a day, B12 above 55 micrograms a day) the risk was nearly double, and higher in men who smoked. Men, B6 above 20 mg a day: HR 1.82; B12 above 55 micrograms a day: HR 1.98 (B6 1.25 to 2.65; B12 1.32 to 2.97) Methods, limits and funding Outcomes: Lung cancer Limitations: Observational: a link, not proof of cause. Supplement use was self-reported. The authors say B vitamins are not protective against lung cancer and may be harmful. Funding and conflicts: No conflict statement in the record read. Read: abstract
Clarke 2010 Effects of lowering homocysteine levels with B vitamins on cardiovascular disease, cancer, and cause-specific mortality: Meta-analysis of 8 randomized trials involving 37 485 individuals. Arch Intern Med · PMID 20937919 · DOI	Systematic review meta analysis	37485 8 large randomised trials in people at increased risk of cardiovascular disease; median follow-up 5 years	Folic acid supplements (as the homocysteine-lowering vitamin) Oral Varied by trial Median 5 years · vs Placebo	Folic acid lowered homocysteine by about 25% on average but had no significant effect on major vascular events, stroke, cancer or death within 5 years. Major vascular events RR 1.01; stroke RR 0.96; cancer RR 1.05; all-cause death RR 1.02 (Major vascular events 0.97 to 1.05; stroke 0.87 to 1.06; cancer 0.98 to 1.13; all-cause death 0.97 to 1.08) Methods, limits and funding Outcomes: Major vascular events, stroke, cancer, death Limitations: Folic acid was the main test vitamin, in people at high heart risk. Not a test of a B-complex product. Funding and conflicts: No conflict statement in the record read. Read: abstract
HPS2-THRIVE Collaborative Group 2014 Effects of extended-release niacin with laropiprant in high-risk patients. N Engl J Med · PMID 25014686 · DOI	Randomised controlled trial	25673 25,673 adults with vascular disease already on statin-based cholesterol treatment	Extended-release niacin (nicotinic acid) with laropiprant, a prescription drug that reduces flushing Oral 2 g niacin with 40 mg laropiprant a day (studied in the trial) Median 3.9 years · vs Matching placebo	Niacin lowered LDL and raised HDL cholesterol a little but did not reduce major vascular events (13.2% versus 13.7%). It increased serious side effects: diabetes-control problems, new diabetes, stomach and gut, muscle, skin, infection and bleeding. Major vascular events rate ratio 0.96; diabetes-control problems +3.7 percentage points; new diabetes +1.3; gut +1.0; muscle +0.7; skin +0.3; infection +1.4; bleeding +0.7 (Major vascular events 0.90 to 1.03) Methods, limits and funding Outcomes: Major vascular events and serious side effects Limitations: A prescription-strength niacin product given to people with heart disease, far above the amounts in ordinary B-complex tablets. It shows what high-dose nicotinic acid can do; it is not a test of B-complex products. Funding and conflicts: Funded by Merck and others, as stated in the abstract. Read: abstract
Kennedy 2010 Effects of high-dose B vitamin complex with vitamin C and minerals on subjective mood and performance in healthy males. Psychopharmacology (Berl) · PMID 20454891 · DOI	Randomised controlled trial	215 215 healthy men aged 30 to 55 in full-time work	High-dose B-complex with vitamin C and minerals (one branded product; name not repeated here) Oral 33 days · vs Placebo	Ratings of stress (PSS), general health (GHQ-12) and the 'vigour' mood scale improved more with the product than with placebo. The product group also did better on one maths task (Serial 3s) and rated themselves less mentally tired. Improvements on PSS, GHQ-12 and POMS vigour; numbers not given in the abstract (Not given in the abstract) Methods, limits and funding Outcomes: Perceived Stress Scale, General Health Questionnaire (GHQ-12), Profile of Mood States, thinking tasks, mental tiredness ratings Limitations: Self-rated measures. The product also contained vitamin C and minerals, so the effect cannot be put down to B vitamins alone. One product, one group (working men), 33 days. Funding and conflicts: Funding not stated in the abstract read. Read: abstract
Lamers 2006 Red blood cell folate concentrations increase more after supplementation with [6S]-5-methyltetrahydrofolate than with folic acid in women of childbearing age. Am J Clin Nutr · PMID 16825690 · DOI	Randomised controlled trial	144 144 healthy women aged 19 to 33	[6S]-5-methyltetrahydrofolate (the 'methyl' form of folate) versus folic acid Oral 416 micrograms of the methyl form, 208 micrograms of the methyl form, or 400 micrograms of folic acid a day (studied in the trial) 24 weeks · vs Placebo	Red blood cell folate rose more with 416 micrograms of the methyl form than with 400 micrograms of folic acid or 208 micrograms of the methyl form. Plasma folate levelled off after 12 weeks; red blood cell folate had not levelled off at 24 weeks. Higher red blood cell folate increase with the equimolar methyl form (P < 0.001) (Not given in the abstract) Methods, limits and funding Outcomes: Red blood cell folate and plasma folate Limitations: Blood folate only; no health outcomes such as birth defects were measured. Women of childbearing age, not other groups. Funding not stated in the abstract. Funding and conflicts: Funding not stated in the abstract read. Read: abstract
Lee 2023 A functional evaluation of anti-fatigue and exercise performance improvement following vitamin B complex supplementation in healthy humans, a randomized double-blind trial. Int J Med Sci · PMID 37786445 · DOI	Randomised crossover trial	32 32 healthy adults aged 20 to 30 (16 men, 16 women), not athletes	One daily tablet with vitamins B1, B2, B6 and B12 (one branded product; name not repeated here) Oral One tablet a day 28 days, then a 14-day washout · vs Placebo	After 28 days the product group ran 1.26 times longer to exhaustion than before and than the placebo group, and had lower blood lactate and ammonia during exercise and in recovery. The authors report no side effects. Running time to exhaustion 1.26-fold (p < 0.05); lower lactate and ammonia (p < 0.05) (Not given in the abstract) Methods, limits and funding Outcomes: Running time to exhaustion, blood lactate and ammonia during and after exercise Limitations: Very small trial. The abstract describes both a crossover design and two groups of 16, which do not fit together cleanly. Treadmill and blood tests, not everyday tiredness. Not repeated by other groups in the sources read. Funding and conflicts: Authors declare no competing financial interests. Read: abstract
Li 2020 AACC Guidance Document on Biotin Interference in Laboratory Tests. J Appl Lab Med · PMID 32445355 · DOI	Guidance document	Guidance for laboratories and clinicians, based on case reports and in vivo and in vitro studies	Biotin (vitamin B7) in high-dose supplements Oral	High circulating biotin can cause falsely high or falsely low results in some blood tests that use biotin binding (biotin-based immunoassays). The amount that causes interference differs by test and by maker. Biotin is cleared fairly quickly, so a repeat test after a pause is an option. Interference shown in case reports and spiking studies (Not applicable) Methods, limits and funding Outcomes: Effect of biotin on blood test results Limitations: A guidance document from a laboratory society. It does not say how many people are affected. Funding and conflicts: No conflict statement in the record read. Read: abstract
Markun 2021 Effects of Vitamin B12 Supplementation on Cognitive Function, Depressive Symptoms, and Fatigue: A Systematic Review, Meta-Analysis, and Meta-Regression. Nutrients · PMID 33809274 · DOI	Systematic review meta analysis	6276 16 randomised trials in people without advanced brain disease or overt B12 deficiency	Vitamin B12 alone, or B12 with folic acid with or without B6 (a B complex) Oral Varied by trial Varied · vs Placebo or control	No evidence of an effect of B12 alone or of a B complex on any thinking skill. No overall effect on depression measures. Only one trial reported fatigue, so no pooled analysis was possible. No effect found on cognition or depression; fatigue not analysable (Not given in the abstract) Methods, limits and funding Outcomes: Thinking skills, depressive symptoms, unexplained fatigue Limitations: Trial products and designs differed. Fatigue was reported by one trial only, so this review cannot say whether B vitamins help with it. Funding and conflicts: Authors declare no conflict of interest. Read: abstract
Martí-Carvajal 2017 Homocysteine-lowering interventions for preventing cardiovascular events. Cochrane Database Syst Rev · PMID 28816346 · DOI	Systematic review meta analysis	71422 15 randomised trials in people with and without existing heart or blood-vessel disease; follow-up 1 to 7.3 years	Supplements of vitamin B6, B9 (folate) or B12, alone or combined, to lower homocysteine Oral Varied by trial 1 to 7.3 years · vs Placebo (and low versus high doses in two trials)	No difference from placebo for heart attack, death from any cause or serious side effects (high-quality evidence). A small difference favoured the vitamins for stroke. Heart attack RR 1.02; death RR 1.01; serious adverse events RR 1.07; stroke RR 0.90 (Heart attack 0.95 to 1.10; death 0.96 to 1.06; serious adverse events 1.00 to 1.14; stroke 0.82 to 0.99) Methods, limits and funding Outcomes: Heart attack, stroke, death from any cause, serious side effects Limitations: These trials used B6, folate and B12, not finished B-complex products, and mostly enrolled people already at high heart risk. The stroke result sits right at the edge of chance. Funding and conflicts: Cochrane review; one author reports past paid teaching workshops for drug companies unrelated to this review. Read: abstract
Maruf 2022 Systematic Review and Meta-Analysis of L-Methylfolate Augmentation in Depressive Disorders. Pharmacopsychiatry · PMID 34794190 · DOI	Systematic review meta analysis	6707 9 articles (6,707 patients) of adults with major depression already taking antidepressants; the pooled analyses used 3 to 4 studies (483 to 507 people)	L-methylfolate added to an antidepressant Oral Varied by study Varied · vs Antidepressant alone	The qualitative review suggests added L-methylfolate improved response to antidepressants. Pooled results showed a small effect. Response RR 1.25 (3 studies, n = 483); depression score SMD -0.38 (4 studies, n = 507) (Response 1.08 to 1.46; depression score -0.59 to -0.17) Methods, limits and funding Outcomes: Depression scores and treatment response Limitations: Few and small studies; people were already on antidepressants. This is one folate form given with medicine, not a B-complex product, and not a treatment for people who are not on an antidepressant. Funding and conflicts: Some authors have links to a genetic-testing company and to pharmacogenomics research groups; no product funding is stated in the record read. Read: abstract
Mazokopakis 2023 The effects of folinic acid and l-methylfolate supplementation on serum total homocysteine levels in healthy adults. Clin Nutr ESPEN · PMID 38056998 · DOI	Randomised controlled trial	272 272 healthy Greek adults (mean age 43) with homocysteine of 10 micromoles per litre or more; people with low B12 also had B12 injections in the first month	Folinic acid versus L-methylfolate Oral 3 months · vs The two forms compared with each other; no placebo group	Homocysteine fell in both groups and the size of the fall did not differ between the two forms. Folinic acid raised blood folate more. People with the MTHFR 677TT gene variant had a bigger fall in homocysteine. Homocysteine fell with both forms; no difference between forms (Not given in the abstract) Methods, limits and funding Outcomes: Blood folate, B12 and homocysteine; MTHFR gene variants Limitations: No placebo group and no folic acid group, so it does not test methylfolate against plain folic acid. Blood marker only. Some people also received B12. Funding and conflicts: No conflict statement in the record read. Read: abstract
Miller 2024 Excess Folic Acid and Vitamin B12 Deficiency: Clinical Implications? Food Nutr Bull · PMID 38987872 · DOI	Narrative review	Review of clinical and population studies on folic acid and B12 status	Folic acid (high-dose supplements and fortification) Oral	People with low B12 and high folate had lower thinking scores and higher homocysteine and methylmalonic acid than people with low B12 and normal folate. High-dose folic acid in people with pernicious anaemia or epilepsy lowered blood B12. The authors say the evidence is mainly correlative or from uncontrolled observations and the explanation has not been tested, but it is compelling enough to watch for B12 deficiency in at-risk people, including older adults. Association, not proven cause (Not applicable) Methods, limits and funding Outcomes: B12 status, thinking scores, homocysteine, methylmalonic acid Limitations: Narrative review. Evidence is mostly correlative or uncontrolled. A proposed mechanism is untested. Funding and conflicts: One author is co-inventor on a patent for a B12 absorption assay and is an associate editor of a nutrition journal. Read: abstract
Muhamad 2023 The Role of Vitamin B6 in Peripheral Neuropathy: A Systematic Review. Nutrients · PMID 37447150 · DOI	Systematic review	20 articles on vitamin B6 and peripheral neuropathy	Vitamin B6 (pyridoxine, pyridoxal, pyridoxamine) Oral Varied	Higher B6 levels, usually from supplements, may lead to a mostly or only sensory, axonal neuropathy. Symptoms were reported to improve after stopping pyridoxine. There is no firm evidence that low B6 causes neuropathy, and a treatment role for B6 cannot be confirmed. B6 as part of a multivitamin at permitted daily amounts has not been proven harmful in people who already have neuropathy. Qualitative; no pooled numbers (Not applicable) Methods, limits and funding Outcomes: Nerve damage (peripheral neuropathy) with high or low B6 Limitations: Search of one database (PubMed); mostly case reports and small studies. It cannot give how common the problem is. Funding and conflicts: Authors declare no conflict of interest. Read: abstract
Pietrzik 2010 Folic acid and L-5-methyltetrahydrofolate: comparison of clinical pharmacokinetics and pharmacodynamics. Clin Pharmacokinet · PMID 20608755 · DOI	Narrative review	Review of studies comparing folic acid with the methyl form of folate	Folic acid versus L-5-methyltetrahydrofolate (the methyl form, sold as a calcium salt) Oral Equimolar amounts compared in the studies reviewed Varied · vs Folic acid	The review says the two forms have comparable activity, absorption and availability at equal molar amounts, and that the methyl form is at least as effective as folic acid for blood folate and homocysteine. It suggests possible advantages for the methyl form (less masking of B12 deficiency, fewer interactions with drugs that block folate recycling) but these are stated as possibilities. Comparable at equal molar amounts (Not applicable) Methods, limits and funding Outcomes: Absorption, blood folate, plasma homocysteine Limitations: A narrative review, not a pooled analysis. The abstract names a commercial brand of the methyl form, and funding is not stated in the abstract. The suggested advantages are not shown by outcome trials in the abstract. Funding and conflicts: Funding not stated in the abstract read; the abstract names a commercial brand of the methyl form. Read: abstract
Pokushalov 2024 Effect of Methylfolate, Pyridoxal-5'-Phosphate, and Methylcobalamin (Soloways(TM)) Supplementation on Homocysteine and Low-Density Lipoprotein Cholesterol Levels in Patients with Methylenetetrahydrofolate Reductase, Methionine Synthase, and Methionine Synthase Reductase Polymorphisms: A Randomized Controlled Trial. Nutrients · PMID 38892484 · DOI	Randomised controlled trial	54 54 adults aged 40 to 75 with raised homocysteine, moderate LDL cholesterol and variants in the MTHFR, MTR or MTRR genes	Methylfolate plus pyridoxal-5'-phosphate (the active form of B6) plus methylcobalamin (one branded combination) Oral 6 months · vs Placebo	Homocysteine fell by 30.0% and LDL cholesterol by 7.5% more than with placebo. The fall in homocysteine was larger in people carrying two copies of the minor gene variants (48.3%) than in mixed carriers (18.6%). Homocysteine -30.0%; LDL cholesterol -7.5% versus placebo (Homocysteine -39.7% to -20.3%; LDL cholesterol -10.3% to -4.7%) Methods, limits and funding Outcomes: Homocysteine and LDL cholesterol Limitations: Only 54 people, with a selected genetic profile. Blood markers only, not heart attacks or strokes. No folic acid or plain-B-vitamin comparison group, so it cannot show that methylated forms beat ordinary forms. Funding and conflicts: Four authors were employed by the company named in the record (Scientific Research Laboratory, Triangel Scientific); the others declare no commercial relationships. Read: abstract
Rutjes 2018 Vitamin and mineral supplementation for maintaining cognitive function in cognitively healthy people in mid and late life. Cochrane Database Syst Rev · PMID 30556597 · DOI	Systematic review meta analysis	83000 28 studies with more than 83,000 cognitively healthy people aged 40 or older; 14 of them (27,882 people, mostly over 60 and often with a history of heart or brain-vessel disease) tested folic acid, B12, B6 or a mix	B vitamins (folic acid, B12, B6 alone or combined), antioxidant vitamins, minerals and combinations Oral Varied by trial At least 3 months; up to 10 years or more · vs Placebo	B vitamins given to cognitively healthy adults, mainly in their 60s and 70s, probably have little or no effect on global cognitive function up to 5 years, and may have none at 5 to 10 years. Three trials of combined supplements (B vitamins, antioxidants, minerals; 6,306 people) found low-certainty little or no effect. Very sparse data on side effects and dementia. B vitamins: SMD -0.03 to 0.06 up to 5 years; -0.01 at 5 to 10 years. Complex supplements: MD 0.12 TICS points after about 8.5 years (Complex supplements: -0.14 to 0.38) Methods, limits and funding Outcomes: Global cognitive function, dementia Limitations: Most trials were not designed to test thinking skills, used brief tests, and rarely reported side effects. Few trials included people younger than 60. Certainty mostly moderate or low. Funding and conflicts: Cochrane review; authors list public research grants and, for some, industry consulting fees outside this work. Read: abstract
Stein 2021 Association between neuropathy and B-vitamins: A systematic review and meta-analysis. Eur J Neurol · PMID 33619867 · DOI	Systematic review meta analysis	46 observational and 7 interventional studies of people with peripheral neuropathy (nerve damage causing numbness, tingling or pain)	B vitamins (B12, B1 and others) as treatment Oral Varied by study Varied · vs Control or placebo	Neuropathy was linked to lower B12 and higher methylmalonic acid and homocysteine. B12 treatment showed a non-significant link with symptom improvement. B1 treatment was linked to improvement. The seven trials combined showed a non-significant higher chance of improvement with B vitamins. Low B12 odds ratio 1.51; B12 treatment 1.36 (4 studies); B1 treatment 5.34 (3 studies); all 7 trials 2.58 (Low B12 1.23 to 1.84; B12 treatment 0.66 to 2.79; B1 treatment 1.87 to 15.19; all 7 trials 0.98 to 6.79) Methods, limits and funding Outcomes: Symptom improvement; B12, methylmalonic acid and homocysteine levels Limitations: Trials were few and mixed in quality, generally did not check vitamin status before treatment, and results varied widely. The abstract reports the B1 result as significant but gives p = 0.059. Funding and conflicts: No conflict statement in the record read. Read: abstract
Viswanathan 2023 Folic Acid Supplementation to Prevent Neural Tube Defects: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA · PMID 37526714 · DOI	Systematic review observational	1244072 12 observational studies (1,244,072 people); 3 studies (990,372) looked at neural tube defects	Folic acid supplements before and/or during pregnancy Oral Before and during pregnancy · vs Women not taking folic acid	One cohort found fewer neural tube defects with folic acid taken before pregnancy, during pregnancy, or both, but only in the later of two time periods studied. No other overall benefits reached significance, and no study found significant harms. The authors say the new evidence agrees with what was found earlier. Adjusted relative risk 0.54 (before), 0.62 (during), 0.49 (before and during) (0.31 to 0.91; 0.39 to 0.97; 0.29 to 0.83) Methods, limits and funding Outcomes: Neural tube defects; harms such as twins, autism, maternal cancer Limitations: Observational studies only, in very highly developed countries. A limited update that looked only at studies since 2015, so it adds to earlier evidence that was not read here. Funding and conflicts: No conflict statement in the record read. Read: abstract
Yamada 2008 Degradation of vitamin B12 in dietary supplements. Int J Vitam Nutr Res · PMID 19326342 · DOI	Laboratory analysis	9 5 vitamin-enriched drinks and 4 solid supplements bought at a retail shop (Japan)	Vitamin B12 in drinks and solid supplements Oral Storage tests over time · vs Label amounts	B12 was below the label in 3 of 5 drinks. Some other drinks held much more B12 than labelled, and in those the B12 fell quickly over time. Only 1 of 4 solid supplements had less than the label. B12 content was affected by storage time, light, temperature and vitamin C, and some B12 may have turned into B12 look-alikes or breakdown products. 3 of 5 drinks and 1 of 4 solid supplements below label (Not applicable) Methods, limits and funding Outcomes: Measured B12 content versus label Limitations: Nine products from one shop in one country in 2008. Shows that mixing nutrients can affect B12, not how common the problem is today. Funding and conflicts: No conflict statement in the record read. Read: abstract
Young 2019 A Systematic Review and Meta-Analysis of B Vitamin Supplementation on Depressive Symptoms, Anxiety, and Stress: Effects on Healthy and 'At-Risk' Individuals. Nutrients · PMID 31527485 · DOI	Systematic review meta analysis	2015 16 randomised placebo-controlled trials (18 articles); 12 were eligible for pooling. Healthy and 'at-risk' groups (poor nutrient status or poor mood).	Daily products with three or more B vitamins Oral Varied by trial At least 4 weeks · vs Placebo	11 of 18 articles reported a better overall mood or mood facet than placebo. Pooled results: a small benefit for stress, no significant benefit for depressive symptoms, and no effect on anxiety. Stress SMD 0.23 (n = 958); depressive symptoms SMD 0.15 (n = 568, p = 0.07); anxiety SMD 0.03 (n = 562, p = 0.71) (Stress 0.02 to 0.45; depressive symptoms -0.01 to 0.32; anxiety -0.13 to 0.20) Methods, limits and funding Outcomes: Mood overall, stress, depressive symptoms, anxiety Limitations: Products and populations differ, so the result does not show which B vitamin did what. The stress benefit is small and its range of uncertainty almost touches zero. Funding and conflicts: Three authors report research funding, honoraria and conference support from the nutrition and supplement industry. Read: abstract
s-efsa-b-vitamins European Food Safety Authority: opinions on B6 upper level and 5-MTHF · Source	Reference database n/a			Methods, limits and funding Read: not-read
s-fda-biotin-communication FDA safety communication on biotin and laboratory tests · Source	Reference database n/a			Methods, limits and funding Read: not-read
s-fda-daily-value FDA: Daily Value on the Nutrition and Supplement Facts Labels (content current as of 2024-03-05) · Source	Reference database n/a			Methods, limits and funding Read: full-text
s-medlineplus-niacin MedlinePlus Medical Encyclopedia: Niacin (review date 2025-01-21) · Source	Reference database n/a			Methods, limits and funding Read: full-text
s-nhs-b-vitamins NHS: Vitamins and minerals, B vitamins and folic acid (page last reviewed 2020-08-03) · Source	Reference database n/a			Methods, limits and funding Read: full-text
s-ods-b-vitamins NIH Office of Dietary Supplements: fact sheets for vitamin B6, niacin, folate and vitamin B12 · Source	Reference database n/a			Methods, limits and funding Read: not-read

What we do not know yet

No trial of a finished B-complex product against everyday tiredness in people who are not deficient was found.
No trial compared health outcomes of methylated forms with ordinary forms.
No head-to-head result for methylcobalamin versus cyanocobalamin was found.
NIH and EFSA fact sheets and opinions could not be read, so official upper limits are not stated.
No survey of heavy metals or undeclared ingredients in B-complex products was found.

How new research is added

New studies are found by a saved PubMed search and placed in a review queue before the page changes.

Lab markers

What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".

Other 4

●

Perceived Stress Scale

Lower stress ratings in trials

A questionnaire in which people rate how stressed they felt in the past month.

Low certainty

Results and what it means

Why it was measured

To see whether a B-vitamin product changes how stressed people feel.

Statistical vs. clinical meaning

A small change in a rating scale, not a medical outcome.

Safety implication

No problem noted in the abstracts.

Study	Result	People	Product
⁶	Better ratings than placebo; numbers not given in the abstract	215 healthy working men aged 30 to 55	High-dose B-complex with vitamin C and minerals for 33 days
²²	Stress SMD 0.23 (95% CI 0.02 to 0.45)	958 people pooled	Three or more B vitamins for at least 4 weeks

^{6 22}

●

Blood lactate and ammonia during exercise

Lower during and after exercise in trials

Chemicals that build up in blood during hard exercise and are used as markers of muscle fatigue.

Not enough evidence

Results and what it means

Why it was measured

To see whether a B-vitamin tablet changes the body's fatigue chemistry during exercise.

Statistical vs. clinical meaning

Lab markers; lower values do not prove people feel less tired in daily life.

Safety implication

No side effects reported.

Study	Result	People	Product
⁸	Lower than placebo (p < 0.05); numbers not given in the abstract	32 healthy adults aged 20 to 30	B1, B2, B6 and B12 tablet for 28 days

⁸

●

Homocysteine

Lower with folate, B6, B12 in trials

An amino acid in blood. Folate, B6 and B12 help the body clear it, so low B vitamins can raise it.

Moderate certainty

Results and what it means

Why it was measured

High levels are linked to heart disease, so B vitamins that lower it were tested.

Statistical vs. clinical meaning

A marker, not a health outcome. Lowering it did not reduce heart attacks in the Cochrane review.

Safety implication

No problem noted.

Study	Result	People	Product
⁴	Folic acid lowered homocysteine by about 25% on average	37,485 people at raised heart risk	Folic acid
¹⁷	-30.0% (95% CI -39.7% to -20.3%) versus placebo	54 adults with raised homocysteine and gene variants	Methylfolate, active B6 and methylcobalamin for 6 months
¹³	Fell in both groups; no difference between folinic acid and L-methylfolate	272 healthy adults	Folinic acid or L-methylfolate for 3 months

^{4 17 13 11}

●

Red blood cell folate

Higher in trials

The folate level inside red blood cells; it reflects folate status over weeks to months.

Low certainty

Results and what it means

Why it was measured

To compare how well folate forms raise folate status.

Statistical vs. clinical meaning

Shows folate status, not birth defects or other outcomes.

Safety implication

No problem noted.

Study	Result	People	Product
⁷	Rose more with 416 micrograms of the methyl form than with 400 micrograms of folic acid (P < 0.001)	144 healthy women aged 19 to 33	Methyl form or folic acid daily for 24 weeks

⁷

Safety

What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.

Main points to know 6

Too much vitamin B6 can damage nerves. A 2023 systematic review says higher B6 levels, usually from supplements, may cause a sensory nerve damage (numbness and tingling). Symptoms were reported to improve after stopping. The NHS says 200 mg or more a day can cause loss of feeling in the arms and legs, that in a few people it became permanent after more than a few months of large amounts, that the effect of 10 mg to 200 mg a day is unclear, and advises not taking more than 10 mg a day of B6 in supplements unless a doctor advises. Many B-complex products contain B6, so check every product you take. Systematic review and authoritative guidance ^{15 27}
High-dose niacin (nicotinic acid) causes flushing and can harm the liver. The NHS says high doses of nicotinic acid can cause skin flushing and, taken for a long time, liver damage. MedlinePlus describes flushing as warmth, redness, itching or tingling of the face, neck, arms or upper chest, reported when niacin is given for high cholesterol, and lists liver damage, higher blood sugar, peptic ulcers and skin rashes with high niacin intake. It says nicotinamide (niacinamide) supplements do not appear to cause flushing. A large trial of prescription-strength extended-release niacin with a flush-blocking drug, in 25,673 people with vascular disease, found more serious side effects (diabetes-control problems, new diabetes, gut, muscle, skin, infection and bleeding) with no drop in major vascular events. That is far above the amounts in ordinary B-complex tablets; it shows what high-dose nicotinic acid can do. Authoritative guidance and randomised trial ^{27 26 5}
Folic acid can hide vitamin B12 deficiency. The NHS says folic acid above 1 mg a day can mask the symptoms of vitamin B12 deficiency, which can eventually damage the nervous system if not found and treated, and that this is a particular concern for older people because B12 is harder to absorb with age. A 2024 review found that high-dose folic acid lowered blood B12 in people with pernicious anaemia or epilepsy, and that people with low B12 and high folate had lower thinking scores; its authors say the evidence is mostly correlative. Authoritative guidance and narrative review ^{27 14}
Biotin can distort blood test results. High circulating biotin can give falsely high or falsely low results in some laboratory tests, depending on the test and the maker. The effect is well documented in case reports and spiking studies. Biotin clears quickly, so a repeat test after a pause is an option. Tell the doctor or laboratory if you take biotin, including in a B complex. Laboratory society guidance ⁹
Single high-dose B6 or B12 supplements and lung cancer in men: a link, not proof. In a cohort of 77,118 adults aged 50 to 76, men who took vitamin B6 or B12 from individual supplements (not from multivitamins) had 30% to 40% more lung cancer. At the highest 10-year average amounts the risk was nearly double, and higher in men who smoked. No link was seen in women. This is observational, so it cannot show cause. The authors conclude B vitamins are not protective and may be harmful. Observational cohort ³
Amounts add up across products and labels can be off. A US government laboratory programme finds that makers often add more than the label says. For multivitamin-mineral products it predicts folic acid is more than 10% above label in the vast majority of adult and children's products. A small 2008 study found B12 below label in 3 of 5 vitamin drinks and, in some drinks, much more than labelled. Taking a B complex with a multivitamin, an energy product and a prenatal can stack B6, niacin and folic acid beyond what any one label shows. Laboratory analysis ^{1 21}

Side effects 6

Effect	How often	Severity and recovery	Evidence
Numbness, tingling or loss of feeling in hands and feet (B6) A 2023 review found no proof that B6 at permitted daily amounts in a multivitamin made existing neuropathy worse.	Not given. NHS: 200 mg or more a day can cause it; effect of 10 to 200 mg a day unclear.	From mild to permanent in a few cases after months of large amounts Usually improves after stopping; can be permanent in a few cases (NHS)	Systematic review and authoritative guidance ^{15 27}
Skin flushing: warmth, redness, itching or tingling of the face, neck and chest (nicotinic acid) Flushing is tied to nicotinic acid, not to nicotinamide (niacinamide), so the form named on the label matters.	Not given in the sources read.	Uncomfortable but not dangerous in itself MedlinePlus: avoid hot drinks and alcohol with niacin to help prevent it; nicotinamide does not appear to cause it.	Authoritative guidance ^{26 27}
Liver damage, higher blood sugar, peptic ulcers, skin rashes with high niacin intake The prescription-strength niacin trial also found more diabetes-control problems and gut, muscle and skin events.	Not given in the sources read.	Can be serious Not stated	Authoritative guidance ^{26 27}
Masked B12 deficiency (folic acid above 1 mg a day) Older adults are more at risk.	Not given.	Can allow nerve damage to progress unnoticed Not stated	Authoritative guidance and narrative review ^{27 14}
Wrong blood test results (biotin) Depends on the test and its maker.	Not given.	Can lead to missed or wrong diagnoses Biotin clears quickly	Laboratory society guidance ⁹
Mild effects in trials of B-complex products Trials were short and small. Rates of stomach upset or nausea were not given in the abstracts read.	The abstracts of the stress, mood and exercise trials report no safety problem; the exercise trial states no side effects.	Not applicable Not applicable	Randomised trials ^{8 22}

Liver

The NHS says taking high doses of nicotinic acid for a long time could lead to liver damage, and MedlinePlus lists liver damage with high niacin intake. Nicotinamide is described by MedlinePlus as not appearing to cause these side effects. A liver-safety reference (LiverTox) was not opened. ^{27 26}

How often. No frequency was found.

Monitoring. No agency monitoring advice was found in the sources read.

This is a safety connection. It is not evidence that B-Complex Formulas supports liver health.

Medicines and supplements 7

With	Why it matters	Importance	Evidence	What to do
Folic acid and vitamin B12 status supplement	Folic acid can correct the anaemia of B12 deficiency without fixing the nerve problem (NHS; 2024 review).	Above 1 mg a day of folic acid can hide B12 deficiency symptoms (NHS).	Authoritative guidance and review Moderate certainty ^{27 14}	Ask a doctor about B12 testing, especially if over 50, vegan, or with stomach or gut disease.
Biotin and laboratory tests laboratory test	Biotin competes in tests that use biotin binding, so results can be falsely high or low (AACC guidance).	Depends on the test and its maker. The abstract read lists no specific tests.	Guidance document Moderate certainty ⁹	Tell the doctor or lab you take biotin before blood tests.
Statin cholesterol medicines plus high-dose nicotinic acid prescription		In people already on statin-based treatment, adding prescription-strength niacin with a flush-blocking drug raised serious side effects compared with placebo.	Randomised trial Moderate certainty ⁵	Ask a doctor or pharmacist before combining niacin with cholesterol medicine.
Drugs that block folate recycling in cells (dihydrofolate reductase inhibitors) prescription	A 2010 review says the methyl form of folate may be associated with a reduced interaction with these drugs.	Stated as a possibility in the review abstract; not tested in outcome trials read here.	Narrative review Not enough evidence ¹⁶	Ask a pharmacist if you take any medicine that works on folate.
Anti-seizure medicines and folic acid prescription	The 2024 review reports high-dose folic acid lowered blood B12 in people with epilepsy.	No interaction with a specific anti-seizure medicine was read.	Narrative review Very low certainty ¹⁴	Ask a doctor before adding folic acid if you have epilepsy.
Prescription medicines in general (other than above) prescription	No mechanism found.	Specific interaction studies for B-complex products with levodopa, methotrexate, metformin, antibiotics, antacids or other medicines were not looked up for this page.	Absence of evidence Not enough evidence	Absence of a study here is not proof of safety. Tell a doctor or pharmacist about all supplements.
Other supplements (multivitamin, energy, prenatal, hair-skin-nails products) supplement	The same B vitamins appear in many products.	Total amounts of B6, niacin, folic acid and biotin can stack; label amounts may also be lower or higher than the real content.	Laboratory analysis Low certainty ^{1 21}	List every product you take and add up each B vitamin with a pharmacist.

Who should check first 6

Situation	Advice	Evidence
Pregnancy and breastfeeding	The NHS recommends a 400 microgram folic acid supplement daily for anyone pregnant, trying, or who could become pregnant, until 12 weeks of pregnancy, and a higher amount for some women with higher risk, on a doctor's advice. A B-complex may or may not match this. Ask a doctor or midwife before using a B-complex while pregnant or breastfeeding. Safety of B6, niacin and other B vitamins at high amounts in pregnancy was not covered in the sources read.	Authoritative guidance ^{27 20}
Children	No trial safety data for B-complex products in children were read. The NHS page read gives its amounts for adults. Children's products have their own page; ask a doctor or pharmacist.	Absence of evidence
Existing nerve symptoms (numbness, tingling)	Numbness can come from low B12 or from too much B6. Ask a doctor before self-treating with B vitamins, and tell them what you take.	Systematic review ^{15 19}
Older adults, vegans, people with stomach or gut disease (B12 risk)	Folic acid can hide B12 deficiency. Ask a doctor about B12 testing.	Authoritative guidance and review ^{27 14}
Liver disease, diabetes, stomach ulcer or taking cholesterol medicine (niacin)	MedlinePlus lists liver damage, higher blood sugar and peptic ulcers with high niacin intake. Ask a doctor first.	Authoritative guidance ²⁶
Planned blood tests	Tell the doctor or lab about biotin before tests.	Guidance document ⁹

Overdose, product quality and regulators

Summary. B vitamins are water-soluble, but several cause harm at high amounts: B6 (nerve damage), nicotinic acid (flushing, liver) and, as a masking problem, folic acid.

Animal. Not reviewed.

High dose or long term signals. B6: nerve damage, sometimes permanent after months of large amounts (NHS). Niacin: liver damage with long-term high doses (NHS, MedlinePlus). Single high-dose B6 and B12 supplements were linked to lung cancer in men in one cohort (observational).

Overdose response. Not found in the sources read. If a child swallows a large number of tablets or gummies, call poison control or emergency services.

Genotoxicity. Not researched.

Label accuracy is better researched than contamination. Heavy-metal or adulterant surveys of B-complex products were not found in the sources read.

Label versus real amounts. US laboratory analyses show makers often add more than the label states; folic acid is predicted to be over label by more than 10% in most multivitamin-mineral products. That is multivitamins in general, not B-complex specifically. ¹

B12 stability. In a small 2008 study of nine products, B12 was below the label in 3 of 5 drinks and 1 of 4 solid products; storage time, light, temperature and vitamin C affected the content. ²¹

Body	Action	Date
NHS / UK Department of Health and Social Care (United Kingdom)	Advice on B-vitamin supplements: unlikely to cause harm at 100 mg or less a day of thiamin, 40 mg or less of riboflavin, 17 mg or less of nicotinic acid or 500 mg or less of nicotinamide, 200 mg or less of pantothenic acid, 0.9 mg or less of biotin, 1 mg or less of folic acid, and 2 mg or less of B12. For vitamin B6 it advises not taking more than 10 mg a day in supplements unless advised by a doctor, and says 200 mg or more a day can cause nerve damage. It says folic acid above 1 mg can mask B12 deficiency, and recommends 400 micrograms of folic acid daily for women who are pregnant or could become pregnant until 12 weeks of pregnancy. These are the regulator's statements, not advice to take any amount. source	2020-08-03
MedlinePlus (US National Library of Medicine) (United States)	Niacin page: describes flushing with niacin given for high cholesterol, says nicotinamide does not appear to cause it, and lists higher blood sugar, liver damage, peptic ulcers and skin rashes with high intake. Lists Recommended Dietary Allowances for niacin: males 14 and over 16 mg a day, females 14 and over 14 mg (18 mg in pregnancy, 17 mg in breastfeeding). source	2025-01-21
US Food and Drug Administration (United States)	Explains that Daily Value (DV) is the reference amount and %DV is how much a serving contributes. Label Daily Values listed for B vitamins: biotin 30 mcg, folate/folic acid 400 mcg DFE, niacin 16 mg NE, pantothenic acid 5 mg, riboflavin 1.3 mg, thiamin 1.2 mg, vitamin B6 1.7 mg, vitamin B12 2.4 mcg. These are label reference values, not advice or limits. source	2024-03-05

When to get medical help

Swelling of the face, lips or tongue, hives, wheezing or trouble breathing after taking a B-complex product: call emergency services.
Numbness, tingling or weakness in the hands or feet that is new, spreading or does not go away: stop the product and see a doctor, and bring the label.
Yellow skin or eyes, dark urine, or pain in the upper right belly after taking high-dose niacin: see a doctor promptly.
A child who has swallowed many tablets or gummies: call poison control or emergency services.
Tiredness with pale skin, sore tongue, or numbness while taking folic acid: ask a doctor about B12 testing.

Stop using the product and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.

General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.

Frequently asked questions

What is a B-complex?

A B-complex product combines several of the eight B vitamins in one product. Which ones, in which forms and in what amounts, differs by product, so read the Supplement Facts panel.

²⁷

Does a B-complex give you energy?

B vitamins help the body release energy from food, but this normal role does not show that extra amounts raise energy when intake is enough. One very small trial of a four-vitamin tablet reported longer running time in healthy young adults. A review found too little data on everyday tiredness to judge.

^{27 8 10}

Is methylated B12 or folate better?

Not shown for health outcomes. One trial found the methyl form of folate raised red blood cell folate more than folic acid. A review says the two act alike at equal molar amounts. A review of B12 forms gives no head-to-head result in its abstract.

^{7 16 2}

Does a B-complex help with stress or mood?

A 2019 pooled review found a small benefit for stress, no clear benefit for depression and none for anxiety. Results were low-certainty and some authors report industry funding.

^{22 6}

Does it help memory?

Reviews found no benefit for thinking skills from B12 alone or B complex in people without deficiency, and a Cochrane review found B vitamins probably have little or no effect on overall thinking in healthy older adults.

^{10 18}

Does it protect the heart?

A Cochrane review of 15 trials found no difference in heart attack or death from any cause; stroke was slightly lower, near the edge of chance. Folic acid trials found no effect on vascular events, cancer or death.

^{11 4}

Why does niacin cause flushing?

MedlinePlus describes flushing as warmth, redness, itching or tingling of the face, neck, arms or upper chest, reported when niacin is given for high cholesterol. Nicotinamide does not appear to cause it. The NHS says high-dose nicotinic acid can also harm the liver over time.

^{26 27}

Can too much vitamin B6 be harmful?

Yes. A 2023 review says higher B6 levels, usually from supplements, can cause a sensory nerve damage. The NHS says 200 mg or more a day can cause numbness in the arms and legs, sometimes permanent, and advises no more than 10 mg a day in supplements unless a doctor advises.

^{15 27}

Can folic acid hide B12 deficiency?

The NHS says more than 1 mg a day of folic acid can hide the symptoms of B12 deficiency, a particular concern for older people. A 2024 review calls the evidence mostly correlative but enough to watch for B12 deficiency.

^{27 14}

Can biotin affect blood tests?

Yes. High biotin can cause falsely high or low results in some laboratory tests, depending on the test and the maker. Tell the doctor or lab you take it.

⁹

Can I take a B-complex in pregnancy?

The NHS recommends a folic acid supplement for anyone pregnant or who could become pregnant. A B-complex may not match that advice, and safety of high amounts of other B vitamins in pregnancy was not covered in the sources read. Ask a doctor or midwife.

^{27 20}

Are the amounts on the label what is in the product?

Not always. A US government laboratory programme predicts multivitamin-mineral products often contain more than the label, including folic acid more than 10% over in most. A small study found B12 below label in some drinks.

^{1 21}

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Editorial transparency

Written by: AlternativeMed editorial team. Research compiled with AI assistance, then checked against the sources listed.
Medical review: None. This page has not been reviewed by a physician or pharmacist.
First published: 2026-10-26
Last substantive update: 2026-10-26
How we research: We re-read PubMed abstracts for every review, trial and laboratory study cited, after checking titles. Only abstracts were read for studies. The NHS, MedlinePlus and FDA pages were read in full. NIH ODS and EFSA pages were blocked, and the FDA biotin communication was not found, so they are marked unverified and nothing is stated from them.
How we rate evidence: See "How we rate evidence" in the Evidence tab.
Independence: No product is promoted on this page. No affiliate links are shown. Some trials and reviews have industry ties, flagged where the abstracts show it.

Sources 28

Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.

Andrews KW, Gusev PA, McNeal M. Dietary Supplement Ingredient Database (DSID) and the Application of Analytically Based Estimates of Ingredient Amount to Intake Calculations.. J Nutr. 2018. PMID 31505677. DOI 10.1093/jn/nxy092. (abstract)
Behringer CR, Kulkarni A, Weinstein A. Vitamin B12: A Comprehensive Review of Natural vs Synthetic Forms of Consumption and Supplementation.. Cureus. 2025. PMID 41362547. DOI 10.7759/cureus.96258. (abstract)
Brasky TM, White E, Chen CL. Long-Term, Supplemental, One-Carbon Metabolism-Related Vitamin B Use in Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort.. J Clin Oncol. 2017. PMID 28829668. DOI 10.1200/JCO.2017.72.7735. (abstract)
Clarke R, Halsey J, Lewington S. Effects of lowering homocysteine levels with B vitamins on cardiovascular disease, cancer, and cause-specific mortality: Meta-analysis of 8 randomized trials involving 37 485 individuals.. Arch Intern Med. 2010. PMID 20937919. DOI 10.1001/archinternmed.2010.348. (abstract)
HPS2-THRIVE Collaborative Group, Landray MJ, Haynes R. Effects of extended-release niacin with laropiprant in high-risk patients.. N Engl J Med. 2014. PMID 25014686. DOI 10.1056/NEJMoa1300955. (abstract)
Kennedy DO, Veasey R, Watson A. Effects of high-dose B vitamin complex with vitamin C and minerals on subjective mood and performance in healthy males.. Psychopharmacology (Berl). 2010. PMID 20454891. DOI 10.1007/s00213-010-1870-3. (abstract)
Lamers Y, Prinz-Langenohl R, Brämswig S. Red blood cell folate concentrations increase more after supplementation with [6S]-5-methyltetrahydrofolate than with folic acid in women of childbearing age.. Am J Clin Nutr. 2006. PMID 16825690. DOI 10.1093/ajcn/84.1.156. (abstract)
Lee MC, Hsu YJ, Shen SY. A functional evaluation of anti-fatigue and exercise performance improvement following vitamin B complex supplementation in healthy humans, a randomized double-blind trial.. Int J Med Sci. 2023. PMID 37786445. DOI 10.7150/ijms.86738. (abstract)
Li D, Ferguson A, Cervinski MA. AACC Guidance Document on Biotin Interference in Laboratory Tests.. J Appl Lab Med. 2020. PMID 32445355. DOI 10.1093/jalm/jfz010. (abstract)
Markun S, Gravestock I, Jäger L. Effects of Vitamin B12 Supplementation on Cognitive Function, Depressive Symptoms, and Fatigue: A Systematic Review, Meta-Analysis, and Meta-Regression.. Nutrients. 2021. PMID 33809274. DOI 10.3390/nu13030923. (abstract)
Martí-Carvajal AJ, Solà I, Lathyris D. Homocysteine-lowering interventions for preventing cardiovascular events.. Cochrane Database Syst Rev. 2017. PMID 28816346. DOI 10.1002/14651858.CD006612.pub5. (abstract)
Maruf AA, Poweleit EA, Brown LC. Systematic Review and Meta-Analysis of L-Methylfolate Augmentation in Depressive Disorders.. Pharmacopsychiatry. 2022. PMID 34794190. DOI 10.1055/a-1681-2047. (abstract)
Mazokopakis EE, Papadomanolaki MG, Papadakis JA. The effects of folinic acid and l-methylfolate supplementation on serum total homocysteine levels in healthy adults.. Clin Nutr ESPEN. 2023. PMID 38056998. DOI 10.1016/j.clnesp.2023.09.002. (abstract)
Miller JW, Smith A, Troen AM. Excess Folic Acid and Vitamin B12 Deficiency: Clinical Implications?. Food Nutr Bull. 2024. PMID 38987872. DOI 10.1177/03795721241229503. (abstract)
Muhamad R, Akrivaki A, Papagiannopoulou G. The Role of Vitamin B6 in Peripheral Neuropathy: A Systematic Review.. Nutrients. 2023. PMID 37447150. DOI 10.3390/nu15132823. (abstract)
Pietrzik K, Bailey L, Shane B. Folic acid and L-5-methyltetrahydrofolate: comparison of clinical pharmacokinetics and pharmacodynamics.. Clin Pharmacokinet. 2010. PMID 20608755. DOI 10.2165/11532990-000000000-00000. (abstract)
Pokushalov E, Ponomarenko A, Bayramova S. Effect of Methylfolate, Pyridoxal-5'-Phosphate, and Methylcobalamin (Soloways(TM)) Supplementation on Homocysteine and Low-Density Lipoprotein Cholesterol Levels in Patients with Methylenetetrahydrofolate Reductase, Methionine Synthase, and Methionine Synthase Reductase Polymorphisms: A Randomized Controlled Trial.. Nutrients. 2024. PMID 38892484. DOI 10.3390/nu16111550. (abstract)
Rutjes AW, Denton DA, Di Nisio M. Vitamin and mineral supplementation for maintaining cognitive function in cognitively healthy people in mid and late life.. Cochrane Database Syst Rev. 2018. PMID 30556597. DOI 10.1002/14651858.CD011906.pub2. (abstract)
Stein J, Geisel J, Obeid R. Association between neuropathy and B-vitamins: A systematic review and meta-analysis.. Eur J Neurol. 2021. PMID 33619867. DOI 10.1111/ene.14786. (abstract)
Viswanathan M, Urrutia RP, Hudson KN. Folic Acid Supplementation to Prevent Neural Tube Defects: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force.. JAMA. 2023. PMID 37526714. DOI 10.1001/jama.2023.9864. (abstract)
Yamada K, Shimodaira M, Chida S. Degradation of vitamin B12 in dietary supplements.. Int J Vitam Nutr Res. 2008. PMID 19326342. DOI 10.1024/0300-9831.78.45.195. (abstract)
Young LM, Pipingas A, White DJ. A Systematic Review and Meta-Analysis of B Vitamin Supplementation on Depressive Symptoms, Anxiety, and Stress: Effects on Healthy and 'At-Risk' Individuals.. Nutrients. 2019. PMID 31527485. DOI 10.3390/nu11092232. (abstract)
. European Food Safety Authority: opinions on B6 upper level and 5-MTHF. . . (not-read)
. FDA safety communication on biotin and laboratory tests. . . (not-read)
. FDA: Daily Value on the Nutrition and Supplement Facts Labels (content current as of 2024-03-05). . . (full-text)
. MedlinePlus Medical Encyclopedia: Niacin (review date 2025-01-21). . . (full-text)
. NHS: Vitamins and minerals, B vitamins and folic acid (page last reviewed 2020-08-03). . . (full-text)
. NIH Office of Dietary Supplements: fact sheets for vitamin B6, niacin, folate and vitamin B12. . . (not-read)

Where to buy

Check the label first. Whatever you buy, look for these:

The amount of the active ingredient per serving, not just the front-label claim
A third-party testing mark (USP, NSF or ConsumerLab)
Other ingredients and allergens
Ask a pharmacist about interactions with your medicines

Talk to a pharmacist or doctor before you start any supplement, especially if you take medicines. See the Safety tab for interactions.

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Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.