Broccoli: Nutrients, What Research Shows and Safety

Broccoli (Brassica oleracea var. italica) is a vegetable in the cabbage family (Brassicaceae). The green flower heads and the tender stalk are eaten, raw or cooked. People eat it for its vitamins, fiber and sulfur-containing plant compounds called glucosinolates. This page covers broccoli as a food and keeps it apart from supplements and from hype.

Read this first

• Warfarin and vitamin K: broccoli is high in vitamin K, which affects how warfarin works. The usual advice is to keep amounts steady from week to week and to tell your care team before big changes, not to avoid it. [1][2]
• Allergy: any food can cause an allergic reaction. For trouble breathing or swelling of the face or throat, call 911. See food allergy basics and emergency signs.
• Gas and bloating: the NHS lists broccoli among foods that can cause gas. [3]
• Evidence in one line: studies of people who eat more broccoli link it with a somewhat lower cancer risk, but these are observational studies and cannot prove cause. We found no trial showing that eating broccoli prevents cancer.

What is in it (USDA values)

USDA FoodData Central, raw broccoli, SR Legacy item 170379. [4] The serving is the USDA household portion of 1 cup chopped (91 g).

% Daily Value uses the FDA 2016 Daily Values; values vary with variety, ripeness and storage. Serving columns are our arithmetic from the USDA per-100 g values.

Broccoli's main plant compounds are glucosinolates, sulfur-containing chemicals that give cruciferous vegetables their pungent smell and bitter taste. During chopping, chewing and digestion they break down into active compounds such as isothiocyanates, including sulforaphane. [5][6] Most evidence that these compounds fight cancer comes from cells and from rats and mice; the National Cancer Institute says human studies have shown mixed results. [5] Broccoli also contains carotenoids; USDA lists lutein plus zeaxanthin in the table above. [4]

What research says

People who eat more broccoli also differ from others in diet, income, exercise and smoking, so a link is not proof that broccoli is the cause. Observational findings cannot show that eating broccoli prevents cancer.

Eaten as food vs taken as a supplement or extract. The studies above looked at the vegetable. Sulforaphane or glucoraphanin capsules and powders are different products, and we did not read supplement trials, so we make no claims about them. See sulforaphane and glucosinolates in cruciferous vegetables and functional foods vs supplements vs medicine. Broccoli sprouts are a separate product with their own food-safety warning; see raw sprouts, raw milk and undercooked foods.

Raw or cooked? Raw broccoli still contains the enzyme myrosinase, which turns glucosinolates into isothiocyanates in the upper gut. When broccoli is cooked, myrosinase is inactivated and the glucosinolates are mostly broken down later in the colon by gut bacteria. [11] A lab study found that myrosinase activity fell by 80% after 3 minutes of stir-frying, and that letting chopped broccoli sit for 90 minutes before stir-frying gave 2.8 times more sulforaphane. [12] These are findings about chemistry, not a recommendation on how to cook it, and no source we read shows that raw or cooked broccoli gives better health results.

How much is a normal serving

• USDA household portion: 1 cup chopped is 91 g; 1 spear (about 5 inches) is 31 g. [4]
• Official figures: the NHS counts 80 g of fresh, canned or frozen vegetables as one portion of its 5 A DAY. [13] The World Health Organization says at least 400 g of fruits and vegetables a day for people older than 10. [14] These figures are information, not a prescription.
• Fresh, frozen and canned: in a lab comparison of eight fruits and vegetables, including broccoli, vitamin content in frozen produce was comparable to fresh and sometimes higher. Riboflavin was higher in frozen broccoli. [15] Commercial freezing includes blanching, which lowers sulforaphane formation as noted above. See fresh, frozen and canned produce.

Safety, allergy and medicines

• Warfarin and other vitamin K questions: NHS names broccoli among sources of vitamin K. [2] MedlinePlus says some foods that contain vitamin K can affect how warfarin works and advises eating consistent amounts of vitamin K foods week to week and not eating large amounts of leafy green vegetables; talk to your doctor before diet changes. [1] For other medicines we did not find a source describing interactions with broccoli as a food. See foods and medicine interactions.
• Gas and bloating: the NHS says cabbage, broccoli, cauliflower and Brussels sprouts can make you pass gas, and that bloating is often caused by gas from some vegetables. [3][16] We did not find a trial of broccoli and gas, so the strength of this effect and who is affected is not established in the sources we read. For persistent bloating, ask a clinician; see foods for gut health and bloating.
• Thyroid: a review found commercial broccoli contains less than 10 µmol of goitrin (a compound that can lower thyroid iodine uptake) per 100 g serving and can be considered of minimal risk; collards, Brussels sprouts and some Russian kale contain more. [17] The 2024 systematic review found no adverse effect on thyroid function from eating brassica vegetables, particularly with adequate iodine. [10] People with thyroid disease or on thyroid medicine should ask their clinician; sources we read give no amounts for them. See cruciferous vegetables.
• Allergy: the sources we read did not give specific data on broccoli allergy, so we make no claim about how common it is. Treat any reaction like any food reaction; see when to seek medical help after a food reaction.
• Kidneys and potassium: broccoli has 6% of the Daily Value for potassium per cup, so it is not a very high-potassium vegetable by this measure. [4] The sources we read did not give broccoli-specific advice for kidney disease; ask your kidney team.
• Pregnancy: the sources we read gave no special caution for broccoli as food. Raw sprouts are a separate food-safety issue (see the sprouts page linked above).
• Pesticide residues: Proper evidence not found; we could not read a USDA Pesticide Data Program or similar source for broccoli this session.

Choosing, storing and food safety

• Choose produce that is not bruised or damaged. Pre-cut or packaged produce should be refrigerated or on ice when you buy it. [18]
• Store perishable produce properly, wash it thoroughly under running water before eating, and cut away damaged or bruised areas. [18]
• Soap, detergent or commercial produce wash is not recommended for washing produce. [18]
• Keep raw produce and cutting boards separate from raw meat, poultry and seafood. [18]

Related pages

• Cruciferous vegetables: broccoli, cabbage, kale and others
• Sulforaphane and glucosinolates in cruciferous vegetables
• Foods and medicine interactions: vitamin K, grapefruit and others
• Raw sprouts, raw milk and undercooked foods: risks
• Fresh, frozen and canned produce
• Foods for gut health and bloating