Kohlrabi: Nutrients, What Research Shows and Safety

Kohlrabi (Brassica oleracea var. gongylodes) belongs to the cabbage family (Brassicaceae), the same group as broccoli, cabbage and kale. The part usually eaten is the round, swollen lower stem, raw or cooked. People eat it for its vitamin C and fiber and because it is one of the cruciferous vegetables. This page keeps the food apart from supplements and from hype, and it is honest that very little research looks at kohlrabi on its own.

Read this first

• Kohlrabi is an ordinary food. As with any food, an allergic reaction is possible. For trouble breathing or swelling of the face or throat, call 911. We did not find a source we could read that describes allergy to kohlrabi in particular. See food allergy basics and emergency signs.
• One cup of raw kohlrabi (135 g) gives about 84 mg of vitamin C, which USDA data put at 93% of the Daily Value. It also has about 4.9 g of fiber. [1]
• Kohlrabi has about 350 mg of potassium per 100 g. People with chronic kidney disease, or on medicines that raise potassium, should ask their care team about potassium in food. [1][7]
• Honest summary: the nutrient numbers are solid. Claims about cancer or heart protection come from studies of cruciferous vegetables as a group, mostly observational, and we found no human trial of kohlrabi itself. [2][5]

What is in it (USDA values)

Source: USDA FoodData Central, "Kohlrabi, raw" (SR Legacy, FDC 168424), with the USDA household portion of 1 cup, 135 g. [1] Per-serving numbers are our arithmetic from the per-100 g values. % Daily Value uses the FDA 2016 Daily Values; values vary with variety, ripeness and storage.

Like other cruciferous vegetables, kohlrabi is listed by the Linus Pauling Institute among vegetables rich in glucosinolates, sulfur-containing plant compounds. When raw vegetables are chopped or chewed, glucosinolates break down into compounds such as isothiocyanates. [2] Most of the work on what these compounds do in the body comes from lab, animal and human studies of other crucifers such as broccoli, not kohlrabi. The one kohlrabi-specific lab paper we saw in the literature search measured isothiocyanate compounds in the vegetable; we did not read its abstract, so we do not describe its results. [5]

What research says

Observational studies can show an association but cannot prove that the vegetable caused the result; people who eat more vegetables also differ in other ways. [2]

Eaten as food vs taken as a supplement or extract. The numbers above are for the whole vegetable. We did not find kohlrabi supplements or extracts tested in human trials, so nothing here applies to a pill or powder. The cholesterol trials used a specially bred broccoli, and a result for one crucifer does not automatically hold for another. [2]

How much is a normal serving

• The USDA household portion for kohlrabi is 1 cup, which is 135 g. [1] This is information, not a prescription.
• The NHS counts 80 g of fresh, canned or frozen vegetables as one portion of its 5 A DAY. [11] The World Health Organization advises at least 400 g of fruits and vegetables a day for people older than 10 (fact sheet date shown 26 January 2026). [10]
• Cooking: boiling inactivates myrosinase, the enzyme that starts glucosinolate breakdown, and reduces glucosinolate content more than steaming, microwaving or stir-frying. [2] We did not find a source on cooking losses of vitamin C in kohlrabi specifically.

Safety, allergy and medicines

• Allergy: any food can cause an allergic reaction. For trouble breathing or swelling of the face or throat, call 911. We did not find a source we could read on kohlrabi allergy specifically. See food allergy basics.
• Thyroid ("goitrogens"): very high intakes of cabbage and turnips caused underactive thyroid in animals. The proposed cause is compounds that may compete with iodine uptake. The Linus Pauling Institute says this does not appear to raise risk unless iodine intake is also low, and one human study found no thyroid effects from 150 g a day of cooked Brussels sprouts for four weeks. [2] The NHS lists too little iodine as a rare cause of underactive thyroid in the UK. [8] People with a thyroid condition who eat large amounts of raw crucifers can ask their clinician.
• Potassium and kidneys: with chronic kidney disease the kidneys may not remove extra potassium, and some medicines can also raise potassium; a special diet may be needed. [7] Kohlrabi is not unusually high, but 1 cup gives about 10% of the Daily Value. [1] See kidney disease, potassium and oxalates in foods.
• Blood thinners (vitamin K): USDA lists only 0.1 mcg of vitamin K per 100 g of raw kohlrabi, so it is not a vitamin K source like leafy greens. [1] See foods and medicine interactions.
• Vitamin C from food: the NHS says over 1,000 mg a day from supplements may cause stomach pain, diarrhea or gas. That figure is about supplements; one cup of kohlrabi supplies far less. [4][1]
• Pregnancy and breastfeeding: we did not find a source we could read about kohlrabi in pregnancy. Ask a clinician about any big change in diet. See foods in pregnancy.
• Bloating: some people notice gas from crucifers. We did not find a source we could read that measures this for kohlrabi, so we make no claim.

Choosing, storing and food safety

• Rinse produce under running water before cutting or peeling, even if you will not eat the skin; do not use soap or produce wash. [9]
• Washing reduces bacteria but does not remove them completely. [9]
• Refrigerate cut or packaged produce, and keep fresh produce away from raw meat, poultry and seafood. [9]
• We did not find an official source on how long kohlrabi keeps; trim any bruised or rotten areas. [9]

Related pages

• Cruciferous vegetables
• Sulforaphane and glucosinolates in cruciferous vegetables
• Observational vs trial evidence in nutrition
• Fresh, frozen and canned produce
• Kidney disease, potassium and oxalates in foods