Skip to content
AlternativeMed

Vitamins, Memory and Dementia: What B12, Folate, E and D Trials Found

What trials found about B vitamins, vitamin E, vitamin D and multivitamins for memory and dementia, keeping healthy older adults separate from people with deficiency or impairment.

Content last updated . This page has not been medically reviewed.

Sudden confusion, new trouble speaking, or weakness on one side of the body is an emergency: call 911 (US) or your local emergency service. For memory changes that come on gradually, see a clinician. The NHS lists problems with memory, understanding and judgement among the symptoms of vitamin B12 or folate deficiency, and says some problems caused by these deficiencies can be irreversible. [1] A blood test and clinician assessment, not a supplement bought to see what happens, is the right first step. See memory changes and when to get help. This page is information only.

Quick answer
In people who are not deficient, vitamin supplements have not been shown to reliably protect memory or prevent dementia. The National Center for Complementary and Integrative Health (NCCIH) reports that research shows a multivitamin or high doses of individual vitamins, such as B vitamins and vitamin D, does not have any clear benefits for cognition in well-nourished people. [2] There are a few signals worth knowing about, covered below, and they come with limits.

What the trials found

VitaminGroup and designWhat the source foundLabel
B6, folic acid, B12A Cochrane review of five trials (879 people) with MCI. [3]No evidence of benefit on cognition from B vitamins for six to 24 months. [3]No good evidence of benefit
B6, folic acid, B12VITACOG: 271 people over 70 with MCI took folic acid 0.8 mg, B12 0.5 mg and B6 20 mg a day, or placebo, for 24 months. [4]Brain shrinkage on MRI was 0.76% a year versus 1.08% on placebo. [4] This is a biomarker, not proof of better memory.Promising but limited
B vitaminsA 2022 meta-analysis of 95 studies (46,175 people). [5]Small gain on a screening test score; folate intake, not B12 or B6, was linked with lower dementia risk in observational data. [5]Mixed
B6, B9, B12A 2025 meta-analysis of 17 trials (5,275 people aged 60 or older). [6]The authors reported a very small benefit on global cognition after omitting outlier studies, which they graded as high certainty. [6]Mixed
Vitamin EA Cochrane review in Alzheimer's disease and MCI. [7]No evidence that alpha-tocopherol prevents progression from MCI to dementia, or improves cognition; moderate-quality evidence from one study that it may slow functional decline in Alzheimer's disease. [7]No good evidence of benefit (cognition)
Vitamin D3VITAL substudies: 3,424 older adults assessed by phone and 794 in person. [8]Vitamin D3 at 2000 IU a day was not associated with cognitive decline over two to three years. [8]No good evidence of benefit
Vitamin DA 2024 meta-analysis of 24 trials (7,557 people). [9]A small positive effect on global cognition, with stronger effects in people with baseline deficiency. [9]Mixed
Multivitamin-mineralCOSMOS-Mind: 2,262 adults, mean age 73, for three years. [10]A statistically significant benefit on global cognition (mean z-score 0.07). [10] Incidence of MCI and dementia did not differ, and power was low. [11]Promising but limited

The multivitamin result is the one to watch, but note the authors' own caution that more work is needed to confirm it in a more diverse group. [10] A later analysis pooling three COSMOS cognitive substudies reported benefits on global cognition and episodic memory, and its authors described the global effect as equivalent to reducing cognitive aging by two years. [12] All of this comes from one trial program, so it is not yet a settled answer.

Healthy adults versus deficient groups

  • Healthy, well-nourished adults: supplement benefits for cognition are unproven. [2]
  • Deficiency: B12 and folate deficiency can affect thinking, and diagnosis and treatment are clinician-led. [1] See vitamin B12 deficiency.
  • Vitamin D: the meta-analysis found larger effects where people started out deficient. [9] Trials in deficient groups do not transfer to people with adequate levels.
  • Biomarkers are not outcomes. Lower homocysteine or less brain shrinkage does not by itself mean better memory. See homocysteine and B vitamins.

Other products sold for memory are covered in nootropic evidence by outcome.

Frequently asked questions

Can vitamins prevent dementia?

No supplement has been shown to. NCCIH says multivitamins or high doses of individual vitamins do not have any clear benefits for cognition in well-nourished people. [2]

Does vitamin B12 help memory?

If you are deficient, treating the deficiency matters, and a clinician should assess it. [1] In trials of B vitamins in MCI, Cochrane found no evidence of benefit on cognition. [3]

Does vitamin E help Alzheimer's disease?

Cochrane found no evidence that it improves cognition, though one study suggested it may slow functional decline. [7]

Does vitamin D protect thinking?

The VITAL substudies found no effect on cognitive decline over two to three years. [8] Some meta-analyses found small effects, stronger where people started deficient. [9]

Should I take a multivitamin for my memory?

One large trial found a small benefit on cognition tests. [10] The authors said confirmation is needed. [10] Ask a clinician or pharmacist, especially if you take medicines.

More details: evidence, limits and cautions

The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.

How to read the evidence labels

Labels used on this page: established nutritional role / deficiency treatment, evidence in adequately nourished people, promising but limited, mixed, insufficient evidence, no good evidence of benefit. Groups differ: people with a low vitamin level or mild cognitive impairment (MCI) are a different question from healthy adults.

Safety and who should ask a clinician
  • Vitamin E: it may interact with anticoagulant and antiplatelet medications, simvastatin, niacin, chemotherapy and radiotherapy. [2] In the SELECT trial, 400 IU a day of vitamin E significantly increased prostate cancer risk. [13] See vitamin E trials.
  • B6: NCCIH reports 1 to 6 g of oral pyridoxine a day for 12 to 40 months can cause severe sensory neuropathy. [2] See vitamin B6 toxicity.
  • B12 and medicines: several types of medications, including proton pump inhibitors and metformin, might adversely affect B12 levels. [2] See medication interactions.
  • Kidney or liver disease, surgery, pregnancy: ask before starting high-dose products. See vitamins and kidney or liver disease and vitamins before surgery.
References
  1. NHS. Vitamin B12 or folate deficiency anaemia. Read 2026-10-23.
  2. National Center for Complementary and Integrative Health (NCCIH). Dietary Supplements and Cognitive Function, Dementia, and Alzheimer's Disease: What the Science Says. Read 2026-10-23.
  3. Vitamin and mineral supplementation for preventing dementia or delaying cognitive decline in people with mild cognitive impairment. The Cochrane database of systematic reviews 2018. PubMed abstract. Read 2026-10-23.
  4. Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled trial. PloS one 2010. PubMed abstract. Read 2026-10-23.
  5. B vitamins and prevention of cognitive decline and incident dementia: a systematic review and meta-analysis. Nutrition reviews 2022. PubMed abstract. Read 2026-10-23.
  6. Efficacy of B Vitamin Supplementation on Global Cognitive Function in Older Adults: A Systematic Review and Meta-analysis. Nutrition reviews 2025. PubMed abstract. Read 2026-10-23.
  7. Vitamin E for Alzheimer's dementia and mild cognitive impairment. The Cochrane database of systematic reviews 2017. PubMed abstract. Read 2026-10-23.
  8. Effect of vitamin D on cognitive decline: results from two ancillary studies of the VITAL randomized trial. Scientific reports 2021. PubMed abstract. Read 2026-10-23.
  9. Effects of Vitamin D Supplementation on Cognitive Outcomes: A Systematic Review and Meta-Analysis. Neuropsychology review 2024. PubMed abstract. Read 2026-10-23.
  10. Effects of cocoa extract and a multivitamin on cognitive function: A randomized clinical trial. Alzheimer's & dementia : the journal of the Alzheimer's Association 2023. PubMed abstract. Read 2026-10-23.
  11. Impact of multivitamin-mineral and cocoa extract on incidence of mild cognitive impairment and dementia: Results from the COcoa Supplement and Multivitamin Outcomes Study for the Mind (COSMOS-Mind). Alzheimer's & dementia : the journal of the Alzheimer's Association 2023. PubMed abstract. Read 2026-10-23.
  12. Effect of multivitamin-mineral supplementation versus placebo on cognitive function: results from the clinic subcohort of the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial and meta-analysis of 3 cognitive studies within COSMOS. The American journal of clinical nutrition 2024. PubMed abstract. Read 2026-10-23.
  13. Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA 2011. PubMed abstract. Read 2026-10-23.
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.