Broccoli.

Broccoli

Brassica oleracea var. italica · also called Brócoli (Spanish), calabrese

Broccoli is a green vegetable of the cabbage family. We eat the flower heads and stalk. It is a good source of vitamin C, vitamin K and folate. People who eat more broccoli have somewhat lower cancer risk in observational studies, but no trial shows it prevents cancer. The main cautions are vitamin K if you take warfarin, wind and bloating, and food poisoning from raw sprouts.

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

About Broccoli

Broccoli is a nutritious vegetable with vitamin C, vitamin K and folate. The studies are mostly about eating patterns and small short trials. It is not a proven remedy.

What it is

Broccoli (Brassica oleracea var. italica) is a vegetable in the cabbage family. People eat the green flower heads and the tender stalk, raw or cooked.

USDA data for raw broccoli: 34 kcal per 100 g. One cup chopped (91 g) has about 31 kcal, 2.4 g fibre, 81 mg vitamin C, 93 micrograms vitamin K, 57 micrograms folate and 288 mg potassium. It also holds lutein and zeaxanthin. Values vary with variety and storage.

Its sulfur-containing compounds, called glucosinolates, give broccoli its sharp smell and bitter taste. When broccoli is chopped or chewed they turn into compounds such as sulforaphane.

^{17 24 19}

What the research shows

People who ate more broccoli had somewhat lower cancer risk in a 2024 review of observational studies. These studies cannot show that broccoli is the reason, and the National Cancer Institute says human results are mixed. No trial shows that eating broccoli prevents cancer.

A few small, short randomised trials used cruciferous vegetables or special broccoli. 18 older adults saw a small fall in blood pressure and in after-meal blood sugar. Two trials of a special high-glucoraphanin broccoli lowered LDL cholesterol. Ordinary broccoli did not lower it significantly.

A broccoli sprout extract missed its main goal in prediabetes, and the study had industry links. An 18-person study found broccoli changed gut bacteria, but not symptoms.

^{3 19 6 7 1 8 12}

Raw, cooked and frozen

Sulforaphane forms when a plant enzyme called myrosinase meets glucoraphanin, as raw broccoli is chopped or chewed. Heat destroys the enzyme. In a lab study, stir-frying cut enzyme activity by 80% in 3 minutes. Letting chopped broccoli stand for 90 minutes before stir-frying gave 2.8 times more sulforaphane.

In 18 people, sulforaphane absorption was about tenfold higher from soup made with fresh broccoli than with commercially frozen broccoli, because the blanching before freezing destroys the enzyme. Gut bacteria can make some sulforaphane when the enzyme is gone.

These are findings about chemistry and absorption, not proof of better health. For vitamins, a lab comparison found frozen produce comparable to fresh and sometimes higher.

^{14 13 15 4 5}

The vegetable versus extracts and special varieties

The cholesterol trials used a special variety bred for more glucoraphanin. The prediabetes trial used a sprout extract. The blood pressure and blood sugar trials used soups of mixed cruciferous vegetables. Results for one form do not carry over to another.

^{1 8 6}

Amounts

This page gives no amounts to eat. Ask a doctor, pharmacist or dietitian what is right for you, especially if you take warfarin or other medicine.

At a glance

Traditional uses history, not proof

Eaten as an everyday vegetable, raw or cooked
Eaten for its vitamins and fibre; a common food is not proof that it prevents or treats any condition

Studied for research

Cancer risk, low certainty (observational studies only)
Heart disease and early death, very low certainty (vegetables as a group)
Blood pressure, low certainty (one tiny trial, a mix of cruciferous vegetables)
LDL cholesterol, low certainty (two trials of a special high-glucoraphanin broccoli)
Blood sugar and type 2 diabetes risk, low to very low certainty
Gut bacteria, very low certainty

Main compounds

Vitamin C
Vitamin K (phylloquinone)
Folate
Fibre
Lutein and zeaxanthin
Glucosinolates, including glucoraphanin
Sulforaphane (formed when raw broccoli is chopped or chewed)

Common forms

Raw florets and stalk
Cooked (steamed, stir-fried, boiled, in soup)
Frozen (blanched first)
Broccoli sprouts and sprout extract (a different product, used in one trial)

Research links: National Cancer Institute: Cruciferous vegetables and cancer prevention · Broccoli consumption and cancer risk, 2024 meta-analysis · MedlinePlus: Warfarin · Research Library · Genes & Biomarkers Library

What it is and its history

Accepted scientific name: Brassica oleracea var. italica
Naming authority: Plenck (listed by GBIF as a synonym of the accepted species Brassica oleracea L.; usageKey 3042863, accepted key 3042845)
Common names: Broccoli (English); Brócoli (Spanish)
Family or group: Brassicaceae (the cabbage or mustard family), which also includes cabbage, cauliflower, kale and Brussels sprouts.
Classification: Plantae > Tracheophyta > Magnoliopsida > Brassicales > Brassicaceae > Brassica > Brassica oleracea
Native range: Not verified from a source read.
Habitat: Not verified from a source read.
What it looks like: Roots: Not verified.; Stems: The tender stalk is eaten as well as the flower heads (our earlier summary; not re-verified).; Leaves: Not verified.; Flowers: The green flower heads (florets) are the main part eaten; not re-verified from a botanical source.
Cultivation: Not verified from a source read.
Harvest and processing: Eaten raw or cooked (steamed, stir-fried, soup). Sold fresh or frozen; commercial frozen broccoli is blanched first. Trials used cooked or soup forms.
Look-alikes and adulterants: Name: Cauliflower and other cruciferous vegetables; Note: Related Brassica vegetables with similar glucosinolates. Results for one do not always carry over to another; several studies here used a mix of cruciferous vegetables.; Name: Broccoli sprouts and sprout extract; Note: A different product from the mature vegetable. The prediabetes trial used an extract, not the vegetable.
Sustainability and conservation: Not assessed.

Photographs

Fresh broccoli close-up — Fresh broccoli.

Traditional use and history history, not clinical proof

Tradition or era	Documented use	Source
Modern food use	No historical source was read. Broccoli is a common vegetable eaten for its vitamins, fibre and plant compounds.	Not verified

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
Glucoraphanin PubChem 9548634	glucosinolate	Florets and sprouts (our earlier summary; not re-verified) Not stated in the sources read	The parent compound of sulforaphane. Broken down by the plant enzyme myrosinase or by gut bacteria. ^{15 13 1}	Human data
Sulforaphane PubChem 5350	isothiocyanate	Formed from glucoraphanin when broccoli is chopped or chewed Not stated in the sources read	Studied for cancer, blood sugar and heart effects. In animals and cell studies it protects cells from DNA damage (NCI). Human results are mixed. Sulforaphane is destroyed by heat along with myrosinase. ^{19 15 14 13}	Animal research
Vitamin K (phylloquinone)	vitamin	Florets and stalk USDA: 102 micrograms per 100 g raw broccoli	Needed for blood clotting (NHS). Affects warfarin. ^{24 23 18}	Human data
Vitamin C and folate	vitamins	Florets and stalk USDA: 89.2 mg vitamin C and 63 micrograms folate (DFE) per 100 g raw broccoli	Nutrients. A lab comparison found frozen broccoli vitamin content comparable to fresh. ^{24 5}	Human data
Goitrin (from progoitrin)	goitrogen	Brassica vegetables Under 10 micromol per 100 g in commercial broccoli (industry-linked review)	Can lower thyroid iodine uptake at high amounts; commercial broccoli is below the level that did so. ^{9 10}	Human data

Mechanisms, receptors and pathways

Target or pathway	Gene or receptor	What was found	Level
Myrosinase and sulforaphane formation	Myrosinase; ESP (epithiospecifier protein)	Chopping or chewing raw broccoli lets myrosinase turn glucoraphanin into sulforaphane. Heat destroys myrosinase. Stir-frying cut myrosinase activity by 80% in 3 minutes in a lab study; commercial blanching and freezing cut sulforaphane absorption about tenfold in 18 people. Gut bacteria can make some sulforaphane when the enzyme is gone. ^{14 13 15 4}	Human data
Anticancer effects of isothiocyanates	Not specified	In rats, mice and cell experiments, indoles and isothiocyanates reduced cancer development in several organs. Human studies show mixed results (NCI). ¹⁹	Animal research
Gut bacteria	Bacteroides gene operon (sprout extract trial)	Broccoli changed gut bacteria composition in 18 adults; in a prediabetes trial, a Bacteroides gene needed to make active sulforaphane was more common in people who responded. ^{12 8}	Human data
Thyroid	Not specified	Goitrin and thiocyanate could lower iodine uptake in theory, but a 2024 systematic review found no harm to thyroid function in humans from brassica vegetables in the diet. ^{10 9}	Human data

Absorption, metabolism and elimination

Absorption: Sulforaphane absorption was about tenfold higher from soup made with fresh broccoli than from commercially frozen broccoli.
Distribution: Not found.
Metabolism: Sulforaphane appeared in plasma and urine as free sulforaphane and as thio-conjugates, and part was converted to erucin.
Elimination: Excreted in urine as conjugates.
Bioavailability: Raw vegetables are broken down by the plant enzyme in the upper gut. Cooked ones reach the colon where bacteria break them down. Storage, temperature and packaging also change what is absorbed.

^{13 4}

Isolated compounds versus whole extracts

The LDL trials used a special high-glucoraphanin broccoli. The prediabetes trial used a broccoli sprout extract. The blood pressure and blood sugar trials used a mix of cruciferous vegetable soups. The cancer data come from people who ate broccoli as food. Results from one form do not carry over to another.

Nutritional composition

Nutrition from USDA FoodData Central (raw broccoli, FDC 170379, last updated 4/1/2019). Per 100 g: 34 kcal, 2.8 g protein, 0.37 g fat, 6.6 g carbohydrate, 2.6 g fibre, 1.7 g sugars, 89 mg vitamin C, 102 micrograms vitamin K, 63 micrograms folate (DFE), 316 mg potassium, 47 mg calcium, 0.17 mg vitamin B-6, 0.21 mg manganese and 31 micrograms vitamin A (RAE), with 1,400 micrograms of lutein plus zeaxanthin. One cup chopped (91 g) therefore gives about 31 kcal, 2.4 g fibre, 81 mg vitamin C, 93 micrograms vitamin K, 57 micrograms folate, 288 mg potassium and 43 mg calcium (our arithmetic from the per-100 g values). Values vary with variety, ripeness and storage. This is a description of the food, not advice on how much to eat.

8benefits and uses looked at

24studies and sources checked

Low certaintybest evidence rating found

5lab markers tracked in trials

5 low certainty3 very low certainty

What was looked at

The 8 benefits and uses checked for Broccoli, each with how strong the evidence is. Tap one to open it.

Cancer risk (people who eat more broccoli)Low certainty
Heart disease and early death (vegetables as a group)Very low certainty
Blood pressure (a mix of cruciferous vegetables)Low certainty
LDL cholesterol (special high-glucoraphanin broccoli)Low certainty
Blood sugar after meals (cruciferous vegetable soups)Low certainty
Type 2 diabetes risk (cruciferous vegetables, observational)Very low certainty
Fasting blood sugar in prediabetes (broccoli sprout extract, a supplement)Low certainty
Gut bacteriaVery low certainty

Lab markers tracked in the studies

24-hour systolic blood pressureLDL cholesterolTriglyceridesFasting blood glucoseBlood sugar after meals

What is Broccoli good for?

The main studied uses and how strong the human evidence is for each. Several results come from a mix of cruciferous vegetables, a special broccoli variety or sprout extract, not ordinary broccoli alone.

Cancer risk (people who eat more broccoli)Low certaintyA 2024 review found lower cancer risk with more broccoli: OR 0.64 in case-control studies, RR 0.89 in cohort studies. Observational only; no trial shows prevention. Heart disease and early death (vegetables as a group)Very low certaintyIn 95 prospective studies, more vegetables and fruit went with lower heart disease, cancer and death risk. Cruciferous vegetables were linked too, but broccoli was not analysed alone. Blood pressure (a mix of cruciferous vegetables)Low certaintyIn 18 older adults, 300 g a day of cruciferous vegetables for 2 weeks lowered 24-hour systolic pressure 2.5 mmHg versus root and squash vegetables. Tiny trial. LDL cholesterol (special high-glucoraphanin broccoli)Low certaintyTwo trials (130 people) found 400 g a week of the special broccoli lowered LDL 5 to 7%. Standard broccoli did not change it significantly. Blood sugar after mealsLow certaintyThe same 18 adults had 0.14 mmol/L lower 2-hour after-meal glucose and steadier glucose on cruciferous soups. Average glucose was unchanged. Type 2 diabetes risk (observational)Very low certaintyFour cohort studies linked the highest cruciferous vegetable intake with 16% lower diabetes risk (SRR 0.84). Cannot show cause. Fasting blood sugar in prediabetes (sprout extract, a supplement)Low certaintyA 12-week trial of a broccoli sprout extract missed its main goal. Fasting glucose fell 0.2 mmol/L overall. The study had industry links and was not about the vegetable. Gut bacteriaVery low certaintyIn 18 healthy adults, 200 g a day of cooked broccoli for 18 days changed the mix of gut bacteria. No health outcome was measured.

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.

Cancer risk (people who eat more broccoli)

Low certainty

People who ate more broccoli had somewhat lower odds of cancer in a 2024 review of observational studies. The link was weaker in the better-designed cohort studies. These studies cannot prove that broccoli is the reason, and no trial shows that eating broccoli prevents cancer.

2 studiesStudies looked at broccoli eaten as a food. Cooked and raw were not s…

Studies, doses and limits

What the trials found

A 2024 meta-analysis pooled 23 case-control studies (12,929 cases, 18,363 controls) and 12 cohort studies (699,482 people). Higher broccoli intake was linked to lower cancer risk: odds ratio 0.64 in case-control studies and relative risk 0.89 in cohort studies. Benefits for single cancer sites appeared only in case-control studies. The National Cancer Institute reports that cohort studies of cruciferous vegetables found little or no link to prostate or colorectal cancer, varied results for lung cancer, and no link to breast cancer in a pooled analysis, while some case-control studies found lower risk. It also notes that recall errors and other healthy habits of vegetable eaters make results hard to read.

Results

Lower cancer risk in people who eat more broccoli, in observational studies only. Mixed results for specific cancers. No trial of broccoli for preventing cancer.

Effect sizes as reported

Case-control OR 0.64 (95% CI 0.58 to 0.70); cohort RR 0.89 (0.82 to 0.96).

Why this rating

Observational evidence only. Case-control studies are open to recall bias and the effect shrinks in cohorts. The National Cancer Institute calls human results mixed.

Form and dose studied

Studies looked at broccoli eaten as a food. Cooked and raw were not separated in the abstracts.

Who was studied

Adults in many countries.

Limits

Cannot show cause. Healthier people may eat more vegetables. Specific cancer sites were not consistent.

Why researchers looked

Broccoli holds glucosinolates, which the body turns into compounds such as sulforaphane that slow tumours in rats, mice and cell experiments.

Traditional use

Broccoli is an everyday vegetable, so there is no long traditional remedy use to report here; being a common food is not proof that it prevents or treats any condition.

Proposed mechanism Preliminary mechanism

Glucosinolates in broccoli are broken down into isothiocyanates such as sulforaphane. In animals and cell studies these compounds protect cells from DNA damage and trigger cell death in cancer cells (National Cancer Institute). Human studies have shown mixed results.

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

See the Safety tab. This page does not suggest broccoli prevents or treats cancer.

^{3 19}

Heart disease and early death (vegetables as a group)

Very low certainty

In a large review of 95 long-term studies, people who ate more vegetables and fruit had lower risk of heart disease, stroke, cancer and early death. Cruciferous vegetables, the group that includes broccoli, were linked to lower heart disease and death, but broccoli was not studied alone.

1 studiesNot about broccoli alone.

Studies, doses and limits

What the trials found

A 2017 meta-analysis of prospective studies found that for fruit and vegetables combined, each 200 g per day was linked to a lower risk of coronary heart disease (RR 0.92), stroke (0.84), cardiovascular disease (0.92), total cancer (0.97) and death from any cause (0.90). Similar links were seen for cruciferous vegetables with cardiovascular disease and all-cause death, and for cruciferous vegetables with total cancer risk. The abstract does not give numbers for the cruciferous group.

Results

Lower risk of heart disease and early death in people who eat more vegetables. For the cruciferous group the abstract gives no numbers.

Effect sizes as reported

Combined fruit and vegetables per 200 g/day: CVD RR 0.92 (0.90 to 0.95); all-cause mortality RR 0.90 (0.87 to 0.93).

Why this rating

Observational, and the key figures are for fruit and vegetables combined. Broccoli itself was not analysed.

Form and dose studied

Not about broccoli alone.

Who was studied

Adults in prospective cohorts.

Limits

Observational. Healthier lifestyles go with eating more vegetables. High heterogeneity for deaths (I2 83%).

Why researchers looked

Vegetable-rich diets are linked to better heart health, so researchers asked which vegetable types matter.

Traditional use

Broccoli is an everyday vegetable, so there is no long traditional remedy use to report here; being a common food is not proof that it prevents or treats any condition.

Proposed mechanism None

The review did not test a mechanism.

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

Nothing specific.

Blood pressure (a mix of cruciferous vegetables)

Low certainty

In one very small trial in older adults with mildly raised blood pressure, eating about 300 g a day of cruciferous vegetables for two weeks lowered 24-hour systolic blood pressure by about 2.5 mmHg compared with root and squash vegetables. The trial used a mix of cruciferous vegetables, not broccoli alone.

1 studiesA mix of cruciferous vegetables, about 300 g a day, eaten as soups wi…

Studies, doses and limits

What the trials found

The VESSEL trial was a randomised crossover trial in 18 adults (median age 68, 16 women) with mildly raised blood pressure. Each person ate about 300 g a day of cruciferous vegetables, and separately root and squash vegetables, for two weeks each. 24-hour systolic blood pressure was 2.5 mmHg lower after cruciferous vegetables (95% CI -4.2 to -0.9; P = 0.002), and daytime pressure was 3.6 mmHg lower. Triglycerides were also lower by 0.2 mmol/L.

Results

A small fall in systolic blood pressure after two weeks of daily cruciferous vegetables, compared with other vegetables.

Effect sizes as reported

24-hour systolic -2.5 mmHg (95% CI -4.2 to -0.9); daytime -3.6 mmHg.

Why this rating

A randomised crossover trial, but only 18 people, 2 weeks, and a mix of vegetables. No one eating no vegetables was tested.

Form and dose studied

A mix of cruciferous vegetables, about 300 g a day, eaten as soups with lunch and dinner. Trial detail, not advice.

Who was studied

Older adults with mildly raised blood pressure, mostly women.

Limits

Tiny trial. Broccoli not separated. The control was another vegetable, not a no-vegetable diet.

Why researchers looked

Observational studies link cruciferous vegetables with fewer heart problems, and researchers wanted to test a possible cause.

Traditional use

Broccoli is an everyday vegetable, so there is no long traditional remedy use to report here; being a common food is not proof that it prevents or treats any condition.

Proposed mechanism None

The authors say the pathways linking cruciferous vegetables and heart disease remain uncertain. The trial did not test a mechanism.

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

If you take blood pressure medicine, do not change it because of a diet study; ask your doctor.

⁶

LDL cholesterol (special high-glucoraphanin broccoli)

Low certainty

In two small trials, eating 400 g a week of a special broccoli bred to hold more glucoraphanin lowered LDL cholesterol by 5 to 7%. Ordinary broccoli did not lower it by a statistically significant amount. The special variety is not the broccoli found in most shops.

1 studies400 g a week of cooked or fresh broccoli florets as food. Trial detai…

Studies, doses and limits

What the trials found

Two independent double-blind trials (130 volunteers in all) gave either 400 g a week of standard broccoli or high-glucoraphanin broccoli for 12 weeks. In study 1 (37 people) the high-glucoraphanin diet cut LDL by 7.1% (95% CI -12.3% to -1.8%) and standard broccoli by 1.8% (not significant). In study 2 (93 people) the figures were 5.1% (-8.1% to -2.1%) and 2.5% (not significant). Combined, the high-glucoraphanin fall was greater than with standard broccoli (p = 0.031).

Results

LDL fell 5 to 7% with the special broccoli. Standard broccoli did not change LDL by a significant amount.

Effect sizes as reported

Study 1: -7.1% HG vs -1.8% standard. Study 2: -5.1% HG vs -2.5% standard.

Why this rating

Two randomised trials, but small, with a special variety and no hard heart outcomes. Funding is not stated in the abstract.

Form and dose studied

400 g a week of cooked or fresh broccoli florets as food. Trial detail, not advice; amounts are not recommended here.

Who was studied

Volunteers in two small trials.

Limits

The result applies to the special variety, not necessarily standard broccoli.

Why researchers looked

Cruciferous-rich diets have been linked to lower LDL cholesterol, and isothiocyanates may be the reason, so researchers tested broccoli with more of their parent compound.

Traditional use

Broccoli is an everyday vegetable, so there is no long traditional remedy use to report here; being a common food is not proof that it prevents or treats any condition.

Proposed mechanism Preliminary mechanism

Isothiocyanates from glucosinolates are proposed to lower LDL. The trial tested the idea but the abstract does not show how it works.

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

If you take cholesterol medicine, keep taking it and ask your doctor.

Blood sugar after meals (cruciferous vegetable soups)

Low certainty

In the same small trial, people who ate cruciferous vegetable soups for two weeks had steadier blood sugar and slightly lower blood sugar for two hours after meals than when they ate root and squash soups. Average blood sugar over the whole period did not change.

1 studiesCruciferous vegetable soups, 300 g a day for 2 weeks. Trial detail, n…

Studies, doses and limits

What the trials found

In the VESSEL randomised crossover trial (18 non-diabetic adults, median age 68, 89% women), 300 g a day of cruciferous vegetable soups for two weeks was compared with root and squash soups. Glucose variability was lower by 2.0 percentage points (95% CI -2.8 to -1.1). Two-hour after-meal glucose was lower by 0.14 mmol/L (95% CI -0.24 to -0.04), driven by dinner. Mean glucose over the whole period was not different (p = 0.411). The authors say the clinical meaning is uncertain. Blood sugar was a pre-specified secondary outcome.

Results

Slightly lower after-meal glucose and less glucose variation, but no change in average glucose.

Effect sizes as reported

After-meal glucose -0.14 mmol/L (95% CI -0.24 to -0.04); variability -2.0%.

Why this rating

A randomised crossover trial but tiny (18 people), short and in people without diabetes, and a secondary outcome.

Form and dose studied

Cruciferous vegetable soups, 300 g a day for 2 weeks. Trial detail, not advice.

Who was studied

Older adults with mildly raised blood pressure, no diabetes.

Limits

Same 18 people as the blood pressure trial. Broccoli not separated from other cruciferous vegetables.

Why researchers looked

Observational studies link cruciferous vegetables with less type 2 diabetes, so researchers tested blood sugar directly.

Traditional use

Broccoli is an everyday vegetable, so there is no long traditional remedy use to report here; being a common food is not proof that it prevents or treats any condition.

Proposed mechanism None

The authors do not report a mechanism in the abstract.

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

If you have diabetes or take diabetes medicine, ask your care team before changing meals.

⁷

Type 2 diabetes risk (cruciferous vegetables, observational)

Very low certainty

A 2016 review of four long-term studies found that people who ate the most cruciferous vegetables had about 16% lower risk of developing type 2 diabetes. Citrus fruit showed no link. This cannot prove cause and broccoli was not analysed alone.

1 studiesCruciferous vegetables eaten as food.

Studies, doses and limits

What the trials found

The meta-analysis included seven prospective cohort studies in all (16,544 cases of type 2 diabetes among 306,723 people, followed 4.6 to 24 years). Four of them covered cruciferous vegetables: highest versus lowest intake gave a summary relative risk of 0.84 (95% CI 0.73 to 0.96), with moderate heterogeneity (I2 54%).

Results

About 16% lower risk with the highest intake of cruciferous vegetables, in four cohort studies.

Effect sizes as reported

SRR 0.84 (95% CI 0.73 to 0.96).

Why this rating

Only four observational studies, moderate heterogeneity, and a vegetable group rather than broccoli.

Form and dose studied

Cruciferous vegetables eaten as food.

Who was studied

Adults followed in prospective cohorts.

Limits

Cannot show cause. Broccoli not separated.

Why researchers looked

Researchers asked whether certain vegetable types, not just vegetables overall, are linked to diabetes.

Traditional use

Broccoli is an everyday vegetable, so there is no long traditional remedy use to report here; being a common food is not proof that it prevents or treats any condition.

Proposed mechanism None

No mechanism was tested in the review.

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

Nothing specific.

¹¹

Fasting blood sugar in prediabetes (broccoli sprout extract, a supplement)

Low certainty

A 12-week trial gave a broccoli sprout extract, not the vegetable, to adults with prediabetes. It missed its main goal. Fasting blood sugar fell slightly overall, and more in a small group found by later analysis. The study had industry links.

1 studiesBroccoli sprout extract capsules or powder: a supplement, not the veg…

Studies, doses and limits

What the trials found

In a randomised, double-blind, placebo-controlled trial, 74 drug-naive adults with prediabetes took a broccoli sprout extract (35 people) or placebo (39 people) once a day for 12 weeks. The extract did not reach the target of a 0.3 mmol/L fall in fasting glucose versus placebo. The overall fall was 0.2 mmol/L (95% CI -0.44 to -0.01; P = 0.04). An exploratory subgroup (mild obesity, low insulin resistance, reduced insulin secretion) had a 0.4 mmol/L fall and a gut-bacteria gene linked to making sulforaphane. Gut side effects occurred; no severe adverse events.

Results

Primary target missed; small overall fall in fasting glucose; subgroup result is exploratory.

Effect sizes as reported

Fasting glucose -0.2 mmol/L (95% CI -0.44 to -0.01).

Why this rating

A good-quality design, but the main goal was missed, subgroups were exploratory, and several authors hold patents or shares in a sulforaphane company.

Form and dose studied

Broccoli sprout extract capsules or powder: a supplement, not the vegetable. The abstract gives no dose.

Who was studied

Adults with prediabetes.

Limits

Supplement results do not carry over to eating broccoli. Exploratory subgroup. Industry-linked.

Why researchers looked

Sulforaphane lowered liver glucose production in earlier work in people with type 2 diabetes.

Traditional use

Broccoli is an everyday vegetable, so there is no long traditional remedy use to report here; being a common food is not proof that it prevents or treats any condition.

Proposed mechanism Preliminary mechanism

Sulforaphane is thought to reduce glucose made by the liver. In this trial, how well gut bacteria turn the precursor into active sulforaphane seemed to matter.

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

Stomach and gut side effects were reported. People with prediabetes should work with their care team.

⁸

Gut bacteria

Very low certainty

In 18 healthy adults, eating cooked broccoli every day for 18 days changed the mix of gut bacteria compared with a control diet. The study measured bacteria, not symptoms or health.

1 studies200 g cooked broccoli a day in the trial. Trial detail, not advice.

Studies, doses and limits

What the trials found

A randomised crossover controlled-feeding study in 18 healthy adults used two 18-day periods with 200 g of cooked broccoli plus 20 g of raw daikon radish a day. Overall bacterial communities differed (P = .03). Firmicutes fell 9% and Bacteroidetes rose 10% relative to control; Bacteroides rose 8%. Effects were strongest in people with a BMI under 26.

Results

Changes in the mix of gut bacteria; no health outcome measured.

Effect sizes as reported

Firmicutes -9% (P = .05); Bacteroidetes +10% (P = .03); Bacteroides +8% (P = .02).

Why this rating

Small trial that measured bacteria only. The test diet included raw daikon radish as well as broccoli.

Form and dose studied

200 g cooked broccoli a day in the trial. Trial detail, not advice.

Who was studied

Healthy adults.

Limits

A change in bacteria is not the same as a health benefit.

Why researchers looked

Gut microbes can break down glucosinolates, so researchers asked whether broccoli changes them.

Traditional use

Broccoli is an everyday vegetable, so there is no long traditional remedy use to report here; being a common food is not proof that it prevents or treats any condition.

Proposed mechanism Preliminary mechanism

Gut bacteria convert glucosinolates; broccoli fibre and compounds may feed some bacteria.

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

Gas and bloating can occur; see the Safety tab.

¹²

Connections to the rest of health

How Broccoli 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

B. Body systems

Connected to	Kind of connection	Evidence status	Context	Studies
Digestive system	Adverse effect or risk	Documented risk	The NHS lists broccoli among foods that can cause wind. Preparation or compound: Broccoli as food	²⁰
Immune System	Biological association	Low certainty	Studied for: Cancer risk (people who eat more broccoli)	^{3 19}
Wellness Prevention	Biological association	Low certainty	Studied for: Cancer risk (people who eat more broccoli)	^{3 19}
Cardiovascular System	Biological association	Very low certainty	Studied for: Heart disease and early death (vegetables as a group) Studied for: Blood pressure (a mix of cruciferous vegetables)	^{2 6 1}
Metabolism Weight	Biological association	Low certainty	Studied for: LDL cholesterol (special high-glucoraphanin broccoli) Studied for: Blood sugar after meals (cruciferous vegetable soups)	^{1 7}
Blood Sugar Support	Biological association	Low certainty	Studied for: Blood sugar after meals (cruciferous vegetable soups) Studied for: Type 2 diabetes risk (cruciferous vegetables, observational)	^{7 11 8}
Gut Health	Biological association	Very low certainty	Studied for: Gut bacteria	¹²

C. Body parts and organs

Connected to	Kind of connection	Evidence status	Context	Studies
Thyroid		Reassuring	A 2024 systematic review found no harm to thyroid function from brassica vegetables in the diet, particularly with enough iodine. Preparation or compound: Brassica vegetables eaten as food	^{10 9}

I. Biomarkers

Connected to	Kind of connection	Evidence status	Context	Studies
24-hour systolic blood pressure	Biological association	Low certainty	Measured in trials: decrease. A lab change is not the same as a health benefit.	⁶
LDL cholesterol	Biological association	Low certainty	Measured in trials: decrease. A lab change is not the same as a health benefit.	¹
Triglycerides	Biological association	Very low certainty	Measured in trials: decrease. A lab change is not the same as a health benefit.	⁶
Fasting blood glucose	Biological association	Low certainty	Measured in trials: mixed. A lab change is not the same as a health benefit.	⁸
Blood sugar after meals	Biological association	Low certainty	Measured in trials: decrease. A lab change is not the same as a health benefit.	⁷

K. Biological pathways

Connected to	Kind of connection	Evidence status	Context	Studies
Vitamin K	Preliminary mechanism	Human	Broccoli is a vitamin K food; vitamin K affects warfarin.	^{24 18}
Sulforaphane	Preliminary mechanism	Human	Formed from glucoraphanin in broccoli; heat reduces how much forms.	^{13 14}

L. Active compounds

Connected to	Kind of connection	Evidence status	Context	Studies
Glucoraphanin	Biological association	Human	The parent compound of sulforaphane. Broken down by the plant enzyme myrosinase or by gut bacteria. Preparation or compound: Florets and sprouts (our earlier summary; not re-verified)	^{15 13 1}
Sulforaphane	Biological association	Animal	Studied for cancer, blood sugar and heart effects. In animals and cell studies it protects cells from DNA damage (NCI). Human results are mixed. Sulforaphane is destroyed by heat along with myrosinase. Preparation or compound: Formed from glucoraphanin when broccoli is chopped or chewed	^{19 15 14 13}
Vitamin K (phylloquinone)	Biological association	Human	Needed for blood clotting (NHS). Affects warfarin. Preparation or compound: Florets and stalk	^{24 23 18}
Vitamin C and folate	Biological association	Human	Nutrients. A lab comparison found frozen broccoli vitamin content comparable to fresh. Preparation or compound: Florets and stalk	^{24 5}
Goitrin (from progoitrin)	Biological association	Human	Can lower thyroid iodine uptake at high amounts; commercial broccoli is below the level that did so. Preparation or compound: Brassica vegetables	^{9 10}

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 changed in 1 lab markers

Tap a number to show only those markers. Counts are markers, not people.

Other1

The evidence

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

Evidence by outcome

Cancer risk (people who eat more broccoli) 2 studies Low certainty Heart disease and early death (vegetables as a group) 1 study Very low certainty Blood pressure (a mix of cruciferous vegetables) 1 study Low certainty LDL cholesterol (special high-glucoraphanin broccoli) 1 study Low certainty Blood sugar after meals (cruciferous vegetable soups) 1 study Low certainty Type 2 diabetes risk (cruciferous vegetables, observational) 1 study Very low certainty Fasting blood sugar in prediabetes (broccoli sprout extract, a supplement) 1 study Low certainty Gut bacteria 1 study Very low certainty

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 started from our existing broccoli summary, re-checked nutrition at USDA FoodData Central, and searched PubMed for human trials, reviews and safety evidence. Only abstracts were read for studies. Items we could not verify are flagged in the research gaps.

Study library: every study we checked 24

Design Research type Year from Search

Study	Design	People	Product, dose, length	Result
Armah 2015 Diet rich in high glucoraphanin broccoli reduces plasma LDL cholesterol: Evidence from randomised controlled trials. Mol Nutr Food Res · PMID 25851421 · DOI	Randomised controlled trial	130 Volunteers in two independent double-blind trials (37 and 93 people)	Standard broccoli or high-glucoraphanin (HG) broccoli, a variety bred to hold more glucoraphanin Florets 400 g per week 12 weeks · vs Standard broccoli	In study 1, HG broccoli lowered LDL cholesterol by 7.1% and standard broccoli by 1.8% (not significant). In study 2, HG broccoli lowered it by 5.1% and standard broccoli by 2.5% (not significant). Combined, the HG fall was significantly greater than standard broccoli (p = 0.031). HG broccoli -7.1% (study 1) and -5.1% (study 2); standard -1.8% and -2.5% (not significant) (Study 1 HG: -12.3% to -1.8%; study 2 HG: -8.1% to -2.1%) Methods, limits and funding Outcomes: Plasma LDL cholesterol Limitations: Special high-glucoraphanin variety, not the broccoli on most shelves. Standard broccoli did not change LDL significantly. Two small trials. Funding and conflicts: Funding and conflicts are not stated in the abstract. Read: abstract
Aune 2017 Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality-a systematic review and dose-response meta-analysis of prospective studies. Int J Epidemiol · PMID 28338764 · DOI	Systematic review meta analysis observational	95 prospective studies (142 publications)	Fruit and vegetable intake, with sub-analyses by type (cruciferous vegetables among them) Fruit and vegetables Per 200 g/day (combined analysis) Prospective follow-up · vs Lower versus higher intake	For fruit and vegetables combined, each 200 g/day was linked to lower risk of coronary heart disease, stroke, cardiovascular disease, total cancer and all-cause death. Inverse links were seen for cruciferous vegetables with cardiovascular disease and all-cause death, and with total cancer risk. Combined, per 200 g/day: cardiovascular disease RR 0.92; total cancer RR 0.97; all-cause mortality RR 0.90 (CVD 0.90-0.95; total cancer 0.95-0.99; mortality 0.87-0.93) Methods, limits and funding Outcomes: Cardiovascular disease, total cancer, death from any cause Limitations: Observational. Cruciferous vegetables were analysed as a group, not broccoli alone, and the abstract does not give the numbers for that group. Heterogeneity was high for mortality (I2 83%). Funding and conflicts: Not stated in the abstract. Read: abstract
Baladia 2024 Broccoli Consumption and Risk of Cancer: An Updated Systematic Review and Meta-Analysis of Observational Studies. Nutrients · PMID 38892516 · DOI	Systematic review meta analysis observational	23 case-control studies (12,929 cases, 18,363 controls) and 12 cohort studies (699,482 people)	Broccoli eaten as food Vegetable · vs Lower versus higher broccoli intake	Inverse link in case-control studies (OR 0.64) and in cohort studies (RR 0.89). Site-specific benefit appeared only in case-control studies. OR 0.64 (case-control); RR 0.89 (cohort) (OR 0.58 to 0.70; RR 0.82 to 0.96) Methods, limits and funding Outcomes: Risk of cancer (any type) Limitations: Observational: cannot show cause. Case-control studies compare people with cancer to others, so memory and recall bias are possible, and the authors say people with cancer ate less broccoli. Cohort evidence was smaller and the link weaker. Authors call for more cohort studies. Funding and conflicts: No conflicts declared. Read: abstract
Barba 2016 Bioavailability of Glucosinolates and Their Breakdown Products: Impact of Processing. Front Nutr · PMID 27579302 · DOI	Narrative review n/a	Not applicable	Cruciferous vegetables Vegetables · vs Raw versus cooked	Eaten raw, the plant enzyme breaks glucosinolates down in the upper gut into isothiocyanates, nitriles, and other products. When the vegetable is cooked first, the enzyme is inactivated and glucosinolates pass to the colon, where gut bacteria break them down. Storage time, temperature and packaging also change what reaches the body. Methods, limits and funding Outcomes: Absorption and breakdown of glucosinolates Limitations: Review of processing and bioavailability. No health outcome. Funding and conflicts: Not stated in the abstract. Read: abstract
Bouzari 2015 Vitamin retention in eight fruits and vegetables: a comparison of refrigerated and frozen storage. J Agric Food Chem · PMID 25526594 · DOI	Laboratory n/a	Not applicable (8 foods, broccoli among them)	Fresh refrigerated versus frozen produce Whole produce Three storage times · vs Refrigerated versus frozen	Overall, the vitamin content of frozen foods was comparable to, and occasionally higher than, that of fresh. For broccoli, riboflavin was higher in frozen than in fresh samples. Beta-carotene dropped drastically in some foods, but the abstract does not list broccoli among them. Methods, limits and funding Outcomes: Ascorbic acid, riboflavin, alpha-tocopherol, beta-carotene Limitations: Lab food analysis of four vitamins. Not a health study. Funding and conflicts: Not stated in the abstract. Read: abstract
Connolly 2024 Cruciferous vegetables lower blood pressure in adults with mildly elevated blood pressure in a randomized, controlled, crossover trial: the VEgetableS for vaScular hEaLth (VESSEL) study. BMC Med · PMID 39218859 · DOI	Randomised crossover trial	18 Australian adults with mildly elevated blood pressure (median age 68, 16 of 18 women)	Cruciferous vegetables (about 300 g/day, with lunch and dinner) Vegetables About 300 g/day Two 2-week periods · vs Root and squash vegetables (same weight)	24-hour systolic blood pressure fell by 2.5 mmHg more after cruciferous than after root and squash vegetables, driven by daytime pressure (-3.6 mmHg). Serum triglycerides were lower by 0.2 mmol/L. 24-h systolic -2.5 mmHg; daytime -3.6 mmHg; triglycerides -0.2 mmol/L (-4.2 to -0.9 (24-h systolic); -0.4 to -0.0 (triglycerides, P = 0.047)) Methods, limits and funding Outcomes: 24-hour systolic blood pressure (primary); triglycerides Limitations: Very small trial (18 people, mostly older women), 2 weeks per diet, a mix of cruciferous vegetables and not broccoli alone (the abstract does not name which). Compared with other vegetables, not with no vegetables. Funding and conflicts: No competing interests declared. Registration: ACTRN12619001294145 Read: abstract
Connolly 2025 Cruciferous vegetables improve glycaemic control compared to root/squash vegetables in a randomized, controlled, crossover trial: The VEgetableS for vaScular hEaLth (VESSEL) study. Diabetes Obes Metab · PMID 40375391 · DOI	Randomised crossover trial	18 Non-diabetic adults with elevated blood pressure (median age 68, 89% women)	Cruciferous vegetable soups (300 g/day) Vegetables 300 g/day Two 2-week periods · vs Root and squash vegetable soups	Glucose variability was lower with cruciferous vegetables (-2.0 percentage points). Two-hour after-meal glucose was lower by 0.14 mmol/L, mostly after dinner. Average glucose over the whole period did not differ. Variability -2.0%; 2-h after-meal glucose -0.14 mmol/L (-2.8 to -1.1; -0.24 to -0.04) Methods, limits and funding Outcomes: Glucose variability and after-meal glucose (flash glucose monitor; pre-specified secondary outcome) Limitations: Same 18 people as the blood pressure trial. A secondary outcome. Not people with diabetes. The authors say the clinical meaning is uncertain. Funding and conflicts: No competing interests declared. Registration: ACTRN12619001294145 Read: abstract
Dwibedi 2025 Effect of broccoli sprout extract and baseline gut microbiota on fasting blood glucose in prediabetes: a randomized, placebo-controlled trial. Nat Microbiol · PMID 39929977 · DOI	Randomised placebo controlled trial	74 Drug-naive adults with prediabetes (35 extract, 39 placebo)	Broccoli sprout extract (a supplement, not the vegetable) Sprouts (extract) Once daily 12 weeks · vs Placebo	The extract did not meet the prespecified primary outcome. Overall fasting glucose fell 0.2 mmol/L versus placebo (95% CI -0.44 to -0.01; P = 0.04). A subgroup found only by exploratory analysis (mild obesity, low insulin resistance, lower insulin secretion) had a 0.4 mmol/L fall. Stomach and gut side effects were seen, but no severe adverse events. Fasting glucose -0.2 mmol/L overall (primary target missed) (-0.44 to -0.01) Methods, limits and funding Outcomes: Fasting blood glucose (primary: a 0.3 mmol/L fall versus placebo) Limitations: Extract, not food. Primary outcome missed. Subgroup results are exploratory and need confirming. Funding and conflicts: Industry-linked: two authors hold patents on sulforaphane for glucose control, licensed to Optisan AB, and one owns stock in it. Lantmannen AB supplied the extract and placebo and co-financed the study. One author co-founded a company making a sulforaphane supplement ingredient (not involved in this study). The authors say the sponsors had no influence on analysis. Registration: NCT03763240 Read: abstract
Felker 2016 Concentrations of thiocyanate and goitrin in human plasma, their precursor concentrations in brassica vegetables, and associated potential risk for hypothyroidism. Nutr Rev · PMID 26946249 · DOI	Narrative review	Not applicable (review and calculations)	Brassica vegetables, including commercial broccoli Vegetables Goitrin per 100 g serving	Radioiodine uptake to the thyroid is inhibited by 194 micromol of goitrin but not by 77 micromol. Commercial broccoli, broccoli rabe and kale of Brassica oleracea contain less than 10 micromol goitrin per 100 g serving and can be considered minimal risk. Collards, Brussels sprouts and some Russian kale contain enough to potentially lower iodine uptake. Broccoli under 10 micromol goitrin per 100 g Methods, limits and funding Outcomes: Goitrin and thiocyanate levels versus thresholds that affect thyroid iodine uptake Limitations: Review with estimates, not a trial of broccoli eaters. Two authors are employed by D'Arrigo Bros. Co., a produce company, so this is an industry-linked source. Funding and conflicts: Two authors are with D'Arrigo Bros. Co. of California (a produce company); the third is a university endocrinologist. Read: abstract
Galanty 2024 Do Brassica Vegetables Affect Thyroid Function?-A Comprehensive Systematic Review. Int J Mol Sci · PMID 38612798 · DOI	Systematic review	123 articles (in vitro, animal and human studies)	Brassica vegetables and extracts Vegetables	The vast majority of results cast doubt on the idea that brassica plants have antithyroid effects in humans. Including brassica vegetables in the daily diet, particularly with adequate iodine intake, poses no adverse effects on thyroid function. No pooled effect size in the abstract Methods, limits and funding Outcomes: Thyroid mass and histology, TSH, T3, T4, iodine uptake Limitations: Mixes lab, animal and human studies. Human data are not broken out in the abstract and broccoli is not analysed alone. Funding and conflicts: No conflicts declared. Read: abstract
Jia 2016 Consumption of citrus and cruciferous vegetables with incident type 2 diabetes mellitus based on a meta-analysis of prospective study. Prim Care Diabetes · PMID 26778708 · DOI	Meta analysis observational	4 prospective cohort studies of cruciferous vegetables (16,544 cases of type 2 diabetes among 306,723 people across the 7 studies in the review)	Cruciferous vegetables eaten as food Vegetables Highest versus lowest intake 4.6 to 24 years · vs Lowest intake	Higher cruciferous vegetable intake was linked to lower risk of type 2 diabetes. Citrus fruit intake was not. SRR 0.84 (cruciferous, highest vs lowest) (0.73 to 0.96) Methods, limits and funding Outcomes: Type 2 diabetes incidence Limitations: Only four cohort studies, observational, moderate heterogeneity (I2 54%). Cruciferous vegetables as a group, not broccoli alone. Funding and conflicts: Not stated in the abstract. Read: abstract
Kaczmarek 2019 Broccoli consumption affects the human gastrointestinal microbiota. J Nutr Biochem · PMID 30317146 · DOI	Randomised crossover controlled feeding	18 18 healthy adults	Cooked broccoli, with a little raw daikon radish Florets 200 g cooked broccoli plus 20 g raw daikon radish per day Two 18-day periods · vs Control diet without them	Bacterial communities differed between diets (P = .03). Broccoli lowered Firmicutes by 9% and raised Bacteroidetes by 10% and Bacteroides by 8% relative to control. Effects were strongest in people with BMI under 26. Firmicutes -9%; Bacteroidetes +10%; Bacteroides +8% Methods, limits and funding Outcomes: Stool bacteria composition Limitations: Small trial. It measured bacteria, not symptoms or health outcomes. The test diet included raw daikon, not broccoli alone. Funding and conflicts: Authors declare no conflict of interest. Read: abstract
Saha 2012 Isothiocyanate concentrations and interconversion of sulforaphane to erucin in human subjects after consumption of commercial frozen broccoli compared to fresh broccoli. Mol Nutr Food Res · PMID 23109475 · DOI	Randomised crossover pharmacokinetic	18 18 healthy volunteers	Lightly cooked broccoli soup made from fresh or commercially frozen florets Florets One portion of soup Single meals · vs Fresh versus frozen broccoli	Sulforaphane bioavailability was about tenfold higher from soups made with fresh than with frozen broccoli. The cause was destruction of myrosinase by the commercial blanching-and-freezing process. Human gut bacteria could also convert glucoraphanin to sulforaphane, erucin and their nitriles. About tenfold difference Methods, limits and funding Outcomes: Sulforaphane in plasma and urine Limitations: Absorption of one compound, not a health outcome. Only 18 people. Funding and conflicts: Not stated in the abstract. Read: abstract
Wu 2018 Hydrolysis before Stir-Frying Increases the Isothiocyanate Content of Broccoli. J Agric Food Chem · PMID 29357241 · DOI	Laboratory n/a	Not applicable (food chemistry)	Stir-fried broccoli Florets Stir-frying for minutes Minutes · vs Direct stir-frying	Half-lives of sulforaphane and total isothiocyanates during stir-frying were 7.7 and 5.9 minutes. Myrosinase activity fell by 80% after 3 minutes of stir-frying. Letting glucosinolates break down for 90 minutes before stir-frying gave 2.8 times more sulforaphane and 2.6 times more total isothiocyanates than direct stir-frying. 2.8 times (sulforaphane) and 2.6 times (total isothiocyanates) Methods, limits and funding Outcomes: Sulforaphane, total isothiocyanates and myrosinase activity Limitations: Lab measurement of chemicals in food. No people were tested and no health outcome was measured. Funding and conflicts: Not stated in the abstract. Read: abstract
Yuanfeng 2021 Approaches for enhancing the stability and formation of sulforaphane. Food Chem · PMID 33601652 · DOI	Narrative review n/a	Not applicable	Sulforaphane from broccoli and other brassicas Vegetables	Ingestion of broccoli releases sulforaphane when the plant enzyme myrosinase, and/or gut bacteria, break down glucoraphanin. Both sulforaphane and myrosinase are damaged by heat, and a protein called ESP can steer the reaction toward sulforaphane nitrile instead. Gut bacteria convert glucoraphanin less efficiently than the plant enzyme. Methods, limits and funding Outcomes: How sulforaphane forms and survives cooking Limitations: Chemistry review. Not a study of health outcomes. Funding and conflicts: Not stated in the abstract. Read: abstract
s-fda-produce FDA: Selecting and Serving Produce Safely · Source	Regulator n/a			Methods, limits and funding Read: full-text
s-gbif-brassica-oleracea GBIF species match: Brassica oleracea var. italica · Source	Reference database n/a			Methods, limits and funding Read: full-text
s-medlineplus-warfarin MedlinePlus: Warfarin · Source	Regulator n/a			Methods, limits and funding Read: full-text
s-nci-cruciferous National Cancer Institute: Cruciferous Vegetables and Cancer Prevention · Source	Health agency n/a			Methods, limits and funding Read: full-text
s-nhs-flatulence NHS: Farting (flatulence) · Source	Health agency n/a			Methods, limits and funding Read: full-text
s-nhs-food-allergy NHS: Food allergy · Source	Health agency n/a			Methods, limits and funding Read: full-text
s-nhs-pregnancy-foods NHS: Foods to avoid in pregnancy · Source	Health agency n/a			Methods, limits and funding Read: full-text
s-nhs-vitamin-k NHS: Vitamin K · Source	Health agency n/a			Methods, limits and funding Read: full-text
s-usda-fdc-170379 USDA FoodData Central: Broccoli, raw (SR Legacy, FDC 170379) · Source	Reference database n/a			Methods, limits and funding Read: full-text

What we do not know yet

No trial has tested whether eating broccoli prevents cancer or heart disease.
Blood pressure, blood sugar and gut findings come from 18 people, a mix of cruciferous vegetables, and short periods.
Cholesterol trials used a special high-glucoraphanin variety, and funding was not stated in the abstract.
Sulforaphane levels in supermarket broccoli, pesticide residues and heavy metals were not researched.
No source gave the rate of broccoli allergy, and children and breastfeeding were not researched.
Native range, cultivation and history were not verified from a source read.

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".

Metabolic 2

●

LDL cholesterol

Decrease in trials

The cholesterol carried in LDL particles, often called bad cholesterol.

Low certainty

Results and what it means

Why it was measured

High LDL is a risk factor for heart disease.

Statistical vs. clinical meaning

A blood marker, not a heart outcome. Applies to a special variety.

Safety implication

Ask your doctor before changing cholesterol treatment.

Study	Result	People	Product
¹	Down 7.1% (study 1) and 5.1% (study 2) with high-glucoraphanin broccoli; standard broccoli 1.8% and 2.5% (not significant).	130 volunteers in two trials	400 g/week broccoli for 12 weeks

●

Triglycerides

Decrease in trials

Fats carried in the blood.

Very low certainty

Results and what it means

Why it was measured

High triglycerides are linked with heart and metabolic risk.

Statistical vs. clinical meaning

Borderline result in a tiny secondary outcome.

Safety implication

None specific.

Study	Result	People	Product
⁶	0.2 mmol/L lower after cruciferous vegetables (95% CI -0.4 to -0.0; P = 0.047).	18 adults with mildly raised blood pressure	About 300 g/day cruciferous vegetables for 2 weeks

⁶

Other 3

●

24-hour systolic blood pressure

Decrease in trials

The top blood pressure number averaged over a full day on a portable monitor.

Low certainty

Results and what it means

Why it was measured

High blood pressure is a risk factor for heart disease and stroke.

Statistical vs. clinical meaning

A small average change in a short trial; not the same as fewer heart attacks.

Safety implication

Do not change blood pressure medicine because of this result.

Study	Result	People	Product
⁶	2.5 mmHg lower after cruciferous vegetables than after root and squash vegetables (95% CI -4.2 to -0.9); daytime 3.6 mmHg lower.	18 adults with mildly raised blood pressure	About 300 g/day cruciferous vegetables for 2 weeks

⁶

↕

Fasting blood glucose

Mixed results in trials

Blood sugar measured after not eating overnight.

Low certainty

Results and what it means

Why it was measured

It is used to detect prediabetes and diabetes.

Statistical vs. clinical meaning

Small average change; the preset goal was missed.

Safety implication

Supplement, not the vegetable.

Study	Result	People	Product
⁸	Down 0.2 mmol/L overall with broccoli sprout extract versus placebo (95% CI -0.44 to -0.01); main target of 0.3 mmol/L not met.	74 adults with prediabetes	Broccoli sprout extract once daily for 12 weeks

⁸

●

Blood sugar after meals

Decrease in trials

Glucose measured for two hours after a meal with a sensor.

Low certainty

Results and what it means

Why it was measured

Large swings after meals are linked with metabolic risk.

Statistical vs. clinical meaning

A very small change in a tiny trial.

Safety implication

None specific.

Study	Result	People	Product
⁷	Two-hour after-meal glucose 0.14 mmol/L lower after cruciferous than root and squash soups (95% CI -0.24 to -0.04); average glucose unchanged.	18 non-diabetic adults	300 g/day cruciferous vegetable soups for 2 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 4

Warfarin: keep broccoli steady, tell your care team about big changes. Broccoli is a good source of vitamin K (NHS), and vitamin K affects how warfarin works. MedlinePlus says to eat consistent amounts of vitamin K foods from week to week and to talk to your doctor before changing your diet. USDA lists 102 micrograms of vitamin K in 100 g of raw broccoli. This is guidance to keep intake steady, not to avoid the food. Authoritative guidance ^{18 23 24}
Gas and bloating. The NHS lists broccoli among foods that can make you pass wind. No trial specific to broccoli was found. Authoritative guidance ²⁰
Raw sprouts carry a food poisoning risk. The FDA says sprouts eaten raw or lightly cooked can carry Salmonella, Listeria and E. coli, because the warm, humid way they grow suits bacteria, even at home. The page names alfalfa and mung bean sprouts; broccoli sprouts are grown the same way but are not named. Cooking produce thoroughly kills harmful bacteria. Authoritative guidance ¹⁶
Allergy. Any food can cause an allergy. The NHS lists the signs and says to call emergency services for swelling of the lips, mouth or throat, or struggling to breathe. No broccoli-specific allergy source was found. Authoritative guidance ²¹

Side effects 2

Effect	How often	Severity and recovery	Evidence
Wind (gas) and bloating The NHS suggests seeing a GP if it affects your life, or if you also have lasting stomach ache or bloating, weight loss or blood in the stool.	Not established	mild Not stated	Authoritative guidance ²⁰
Stomach and gut side effects with broccoli sprout extract (a supplement) Gut side effects but no severe adverse events in a 12-week trial of the extract. This is not the vegetable.	Not established	Not stated in the abstract Not stated	Controlled trial ⁸

Liver

No liver injury from eating broccoli was found in the sources read. LiverTox was not checked.

How often. No frequency was found.

Monitoring. No agency monitoring advice was found.

This is a safety connection. It is not evidence that Broccoli supports liver health.

Medicines and supplements 2

With	Why it matters	Importance	Evidence	What to do
Warfarin (blood thinner) prescription	Broccoli contains vitamin K, which the body uses for blood clotting, and warfarin works against vitamin K.	MedlinePlus advises consistent weekly amounts of vitamin K foods, not large amounts of leafy green vegetables, and a talk with your doctor before changes. The page text read does not name broccoli, but the NHS lists it as a vitamin K source.	Authoritative guidance Moderate certainty ^{18 23 24}	Do not suddenly eat much more or much less. Tell your clinic about big changes. Do not stop warfarin yourself.
Other blood thinners, thyroid medicines, cholesterol or blood pressure medicines prescription	Not researched for broccoli.	No source read describes an interaction. Absence of evidence is not proof of safety.	None found Not enough evidence	Ask a pharmacist if you take regular medicine and plan to change how much broccoli you eat.

Who should check first 5

Situation	Advice	Evidence
Taking warfarin	Keep broccoli amounts steady week to week and tell your care team about big diet changes.	Authoritative guidance ^{18 23}
Thyroid disease	A 2024 systematic review found no harm to thyroid function from brassica vegetables in the diet, especially with enough iodine, and an industry-linked review calls commercial broccoli minimal risk. If you have a thyroid condition, ask your clinician about large amounts or concentrated products.	Systematic review ^{10 9}
Pregnancy and breastfeeding	The NHS pregnancy foods-to-avoid list does not include broccoli and says most foods are safe. No source read gave a broccoli-specific warning. Breastfeeding was not researched. Ask your midwife or doctor.	Authoritative guidance ²²
Known allergy to broccoli or other brassica vegetables	Avoid the food that triggers symptoms and ask an allergist. Call emergency services for trouble breathing or swelling of the face or throat.	Authoritative guidance ²¹
Children	No broccoli-specific source on children was read. Ask a doctor or dietitian for advice about your child.	None found

Overdose, product quality and regulators

Summary. No toxicity from broccoli as ordinary food was found in the sources read. The questions are warfarin, wind, thyroid and raw sprouts.

Animal. Not reviewed.

Human doses studied. Trials used about 300 g a day of cruciferous vegetables for 2 weeks, 200 g a day of cooked broccoli for 18 days, and 400 g a week for 12 weeks. They were not designed to measure long-term safety.

Overdose response. Not found.

Genotoxicity. Not researched.

Toxic or hazardous parts. No toxic part identified in the sources read.

Washing produce reduces dirt and germs. Pesticide residues and heavy metals on broccoli were not researched.

Food safety handling. The FDA says to wash all produce under running water, not to use soap or commercial produce wash, to refrigerate cut produce at 40 F or below, and that cooking thoroughly kills harmful bacteria. ¹⁶

Raw sprouts. Raw or lightly cooked sprouts can carry Salmonella, Listeria and E. coli, even if grown at home. The FDA page names alfalfa and mung bean sprouts. ¹⁶

Body	Action	Date
FDA (US Food and Drug Administration) (United States)	Consumer page on selecting and serving produce safely: wash under running water, no soap or produce wash, and raw or lightly cooked sprouts can carry bacteria. source
MedlinePlus (US National Library of Medicine) (United States)	Warfarin drug information: keep vitamin K food intake consistent week to week; talk to your doctor before diet changes. source
NHS (UK) (United Kingdom)	Vitamin K page names broccoli as a source; flatulence page lists broccoli among foods that can cause wind; pregnancy foods-to-avoid page does not list it. source	2026-04-02

When to get medical help

Trouble breathing, swelling of the lips, face or throat, or widespread hives after eating broccoli
Severe or lasting vomiting or diarrhoea after eating raw sprouts (possible food poisoning)
Unusual bleeding or bruising if you take warfarin (contact your clinic)

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

Is broccoli good for you?

It is a nutritious vegetable with vitamin C, vitamin K, folate and fibre. Eating more vegetables is linked to better health, but most broccoli-specific claims rest on observational studies or small trials.

^{24 2}

Does broccoli prevent cancer?

Not shown. People who eat more broccoli had somewhat lower cancer risk in observational studies, but they cannot prove cause. No trial shows broccoli prevents cancer, and the National Cancer Institute calls human results mixed.

^{3 19}

What is sulforaphane?

A compound that forms when raw broccoli is chopped or chewed. It is studied in the lab and in some trials, but supplements and food are not the same thing.

^{15 19}

Is raw or cooked broccoli better?

Raw broccoli forms more sulforaphane because heat destroys the enzyme that makes it. That is a chemistry finding, not proof of better health. Gut bacteria can make some sulforaphane from cooked broccoli.

^{14 4}

Is frozen broccoli as healthy as fresh?

For vitamins, a lab study found frozen produce comparable to fresh, sometimes higher. But commercial blanching before freezing cut sulforaphane absorption about tenfold in 18 people.

^{5 13}

Does broccoli lower cholesterol?

In two trials, a special high-glucoraphanin broccoli lowered LDL cholesterol by 5 to 7%. Standard broccoli did not lower it significantly.

Does broccoli lower blood pressure?

One tiny trial found a mix of cruciferous vegetables lowered systolic pressure about 2.5 mmHg in 2 weeks versus other vegetables. Broccoli was not tested alone.

⁶

Does broccoli help with blood sugar or diabetes?

Evidence is weak. Cruciferous vegetable soups lowered after-meal glucose slightly in 18 people, and observational studies link them to less type 2 diabetes. A sprout extract missed its main goal in prediabetes.

^{7 11 8}

Can I eat broccoli if I take warfarin?

Usually yes, if your intake stays steady. Broccoli is high in vitamin K, which affects warfarin. MedlinePlus says to eat consistent amounts week to week and talk to your doctor before diet changes.

^{18 23 24}

Does broccoli cause gas?

It can. The NHS lists broccoli among foods that can make you pass wind. No broccoli-specific trial was found.

²⁰

Is broccoli bad for the thyroid?

A 2024 systematic review found no harm to thyroid function from brassica vegetables in the diet, particularly with enough iodine. If you have a thyroid condition, ask your clinician.

^{10 9}

Are raw broccoli sprouts safe?

Raw or lightly cooked sprouts can carry Salmonella, Listeria and E. coli, says the FDA, even if grown at home. Cooking thoroughly kills harmful bacteria.

¹⁶

Explore by health goal

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 started from our existing broccoli summary, re-checked nutrition at USDA FoodData Central, and searched PubMed for human trials, reviews and safety evidence. Only abstracts were read for studies. Items we could not verify are flagged in the research gaps.
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.

Sources 24

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

Armah CN, Derdemezis C, Traka MH, Dainty JR, Doleman JF, Saha S, Leung W, Potter JF, Lovegrove JA, Mithen RF.. Diet rich in high glucoraphanin broccoli reduces plasma LDL cholesterol: Evidence from randomised controlled trials.. Mol Nutr Food Res. 2015. PMID 25851421. DOI 10.1002/mnfr.201400863. (abstract)
Aune D, Giovannucci E, Boffetta P, Fadnes LT, Keum N, Norat T, Greenwood DC, Riboli E, Vatten LJ, Tonstad S.. Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality-a systematic review and dose-response meta-analysis of prospective studies.. Int J Epidemiol. 2017. PMID 28338764. DOI 10.1093/ije/dyw319. (abstract)
Baladia E, Moñino M, Pleguezuelos E, Russolillo G, Garnacho-Castaño MV.. Broccoli Consumption and Risk of Cancer: An Updated Systematic Review and Meta-Analysis of Observational Studies.. Nutrients. 2024. PMID 38892516. DOI 10.3390/nu16111583. (abstract)
Barba FJ, Nikmaram N, Roohinejad S, Khelfa A, Zhu Z, Koubaa M.. Bioavailability of Glucosinolates and Their Breakdown Products: Impact of Processing.. Front Nutr. 2016. PMID 27579302. DOI 10.3389/fnut.2016.00024. (abstract)
Bouzari A, Holstege D, Barrett DM.. Vitamin retention in eight fruits and vegetables: a comparison of refrigerated and frozen storage.. J Agric Food Chem. 2015. PMID 25526594. DOI 10.1021/jf5058793. (abstract)
Connolly EL, Liu AH, Radavelli-Bagatini S, et al.. Cruciferous vegetables lower blood pressure in adults with mildly elevated blood pressure in a randomized, controlled, crossover trial: the VEgetableS for vaScular hEaLth (VESSEL) study.. BMC Med. 2024. PMID 39218859. DOI 10.1186/s12916-024-03577-8. (abstract)
Connolly EL, Liu AH, Woodman RJ, Shafaei A, Wood LG, Mithen R, James AP, Schultz CJ, Gan SK, Bondonno CP, Lewis JR, Hodgson JM, Blekkenhorst LC.. Cruciferous vegetables improve glycaemic control compared to root/squash vegetables in a randomized, controlled, crossover trial: The VEgetableS for vaScular hEaLth (VESSEL) study.. Diabetes Obes Metab. 2025. PMID 40375391. DOI 10.1111/dom.16467. (abstract)
Dwibedi C, Axelsson AS, Abrahamsson B, Fahey JW, Asplund O, Hansson O, Ahlqvist E, Tremaroli V, Bäckhed F, Rosengren AH.. Effect of broccoli sprout extract and baseline gut microbiota on fasting blood glucose in prediabetes: a randomized, placebo-controlled trial.. Nat Microbiol. 2025. PMID 39929977. DOI 10.1038/s41564-025-01932-w. (abstract)
Felker P, Bunch R, Leung AM.. Concentrations of thiocyanate and goitrin in human plasma, their precursor concentrations in brassica vegetables, and associated potential risk for hypothyroidism.. Nutr Rev. 2016. PMID 26946249. DOI 10.1093/nutrit/nuv110. (abstract)
Galanty A, Grudzińska M, Paździora W, Służały P, Paśko P.. Do Brassica Vegetables Affect Thyroid Function?-A Comprehensive Systematic Review.. Int J Mol Sci. 2024. PMID 38612798. DOI 10.3390/ijms25073988. (abstract)
Jia X, Zhong L, Song Y, Hu Y, Wang G, Sun S.. Consumption of citrus and cruciferous vegetables with incident type 2 diabetes mellitus based on a meta-analysis of prospective study.. Prim Care Diabetes. 2016. PMID 26778708. DOI 10.1016/j.pcd.2015.12.004. (abstract)
Kaczmarek JL, Liu X, Charron CS, Novotny JA, Jeffery EH, Seifried HE, Ross SA, Miller MJ, Swanson KS, Holscher HD.. Broccoli consumption affects the human gastrointestinal microbiota.. J Nutr Biochem. 2019. PMID 30317146. DOI 10.1016/j.jnutbio.2018.09.015. (abstract)
Saha S, Hollands W, Teucher B, Needs PW, Narbad A, Ortori CA, Barrett DA, Rossiter JT, Mithen RF, Kroon PA.. Isothiocyanate concentrations and interconversion of sulforaphane to erucin in human subjects after consumption of commercial frozen broccoli compared to fresh broccoli.. Mol Nutr Food Res. 2012. PMID 23109475. DOI 10.1002/mnfr.201200225. (abstract)
Wu Y, Shen Y, Wu X, Zhu Y, Mupunga J, Bao W, Huang J, Mao J, Liu S, You Y.. Hydrolysis before Stir-Frying Increases the Isothiocyanate Content of Broccoli.. J Agric Food Chem. 2018. PMID 29357241. DOI 10.1021/acs.jafc.7b05913. (abstract)
Yuanfeng W, Chengzhi L, Ligen Z, Juan S, Xinjie S, Yao Z, Jianwei M.. Approaches for enhancing the stability and formation of sulforaphane.. Food Chem. 2021. PMID 33601652. DOI 10.1016/j.foodchem.2020.128771. (abstract)
. FDA: Selecting and Serving Produce Safely. . . (full-text)
. GBIF species match: Brassica oleracea var. italica. . . (full-text)
. MedlinePlus: Warfarin. . . (full-text)
. National Cancer Institute: Cruciferous Vegetables and Cancer Prevention. . . (full-text)
. NHS: Farting (flatulence). . . (full-text)
. NHS: Food allergy. . . (full-text)
. NHS: Foods to avoid in pregnancy. . . (full-text)
. NHS: Vitamin K. . . (full-text)
. USDA FoodData Central: Broccoli, raw (SR Legacy, FDC 170379). . . (full-text)

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.