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Kohlrabi
Kohlrabi · (Brassica oleracea var. gongylodes)
Cabbage family (Brassicaceae)
Description
With kohlrabi you eat neither root nor leaf but the swollen stem — a bulb that sits above the soil, ringed with leaf stalks. It is harvested from May to October; picked young it is tender and almost fibre-free, while large bulbs turn woody. At around 62 milligrams of vitamin C per 100 grams the raw bulb outdoes many citrus fruits, and it also supplies potassium, copper and mustard-oil glycosides such as glucoraphanin, from which chewing releases sulforaphane. The leaves usually go in the bin, yet they hold about twice the vitamin C and many times the provitamin A of the bulb — young and lightly steamed they make a vegetable in their own right. Kohlrabi counts as especially mild and easy to digest; only in very large amounts over weeks can its mustard oils hinder the thyroid's uptake of iodine.
Kohlrabi is exceptionally rich in vitamin C: the swollen stem contains approx. 62 mg/100 g (approx. 69–102 % of daily requirement). This exceeds many citrus fruits. Other important nutrients: potassium (approx. 350–380 mg/100 g), copper (approx. 0.13 mg/100 g, 14 % DV), vitamin B6 (approx. 0.15 mg/100 g) and dietary fibre (approx. 3.6 g/100 g). Eaten raw in slices as a snack, grated in salad or as crudités — raw preserves the highest vitamin C content, as vitamin C is heat-sensitive. The skin is woody-fibrous and peeled before raw consumption.
In German and Central European culinary tradition, kohlrabi is a typical spring and summer vegetable for children and convalescents — mild, easy to digest, low in fibre when young. Folk medicine recommends kohlrabi for digestive complaints and as a gentle diet for stomach problems. Young leaves (especially rich in vitamin C — approx. twice as much as the bulb) are prepared like leaf vegetables. In parts of France the bulbs are grated and preserved by fermentation like sauerkraut.
In the Indian Ayurvedic tradition, kohlrabi (known as 'Ganth Gobi') is recommended for pitta disorders (states of overheating in the body) — as a cooling, refreshing food. In Kashmir, kohlrabi (Mŏnji) is served with leaves and stem as a main dish with light broth over rice. Furthermore, traditional European folk medicine used kohlrabi for cold symptoms and general fatigue — plausible given its high vitamin C content.
Kohlrabi leaves are nutritionally significant: they contain approx. twice as much vitamin C and approximately 100 times the carotin (provitamin A) compared with the bulb. Young leaves can be used raw in salads, as soup or sautéed like cabbage. In the folk medicine of South Asia and the eastern Mediterranean, kohlrabi leaves are used for colds and inflammation. Older leaves are blanched before consumption to reduce bitter compounds.
In traditional Indian medicine and parts of the Middle East, kohlrabi juice is applied externally to the scalp for hair loss — a folk practice without clinical evidence. Internally: the high vitamin C content supports collagen synthesis (relevant for skin, wounds, connective tissue). Kohlrabi also contains glucosinolates that are hydrolysed to isothiocyanates and show chemoprotective activity in laboratory studies.
Kohlrabi contains glucosinolates (sulphur-containing secondary compounds), including glucoraphanin, glucoiberin, glucobrassicin and others. When cut or chewed, these are hydrolysed by the enzyme myrosinase to isothiocyanates (incl. sulforaphane, indole-3-carbinol). These compounds are associated in epidemiological studies and laboratory experiments with prevention of colorectal and prostate cancer. Goitrogenic effect (thyroid inhibition) possible at very high intake.
Kohlrabi is classically steamed or cooked as a side dish (with butter and herbs), processed into purée, used in stews and soups or for stuffings and gratins. In parts of Germany and Austria, kohlrabi cream soup is a classic home recipe. The mild, slightly sweet flavour results from malic acid, citric acid and natural sugars. Steaming and brief cooking preserve glucosinolates better than prolonged boiling.
Kohlrabi is a mild, well-tolerated vegetable. At very high and regular consumption (several hundred grams daily over weeks), glucosinolate breakdown products can act goitrogenically and inhibit iodine uptake into the thyroid gland — clinically insignificant at normal dietary amounts. Persons with thyroid disorders and iodine deficiency should avoid extreme amounts. On heating, glucosinolates and their breakdown product sulforaphane are partially inactivated — raw or briefly steamed kohlrabi contains the most glucosinolates.
Kohlrabi is safe in normal food amounts in pregnancy and lactation. A valuable source of vitamin C and potassium. Avoid extreme amounts as a precaution (goitrogenic effect at very high intake).
Safe in normal food amounts. Kohlrabi, like other Brassicaceae, may promote flatulence in some infants (via breast milk) — temporarily reduce if intolerance occurs.
Kohlrabi is well suited from weaning age (approx. 7–8 months) — mild, slightly sweet, low in fibre in young bulbs. Steam soft for young children. Suitable as raw snack for older children from approx. 2 years.
Drug interactions
Schilddrüsenhormonpräparate / Jodide
Glucosinolate breakdown products (goitrin, thiocyanates) can competitively inhibit iodine uptake into the thyroid and impair thyroid function in iodine deficiency. Clinically insignificant at normal consumption levels; when taking thyroid medications with very high crucifer intake, consulting a physician is advisable.
Contraindications
- Known thyroid disorder with iodine deficiency — avoid very high consumption amounts; normal food portions are safe.
- Known hypersensitivity to Brassicaceae — avoid kohlrabi.
Harvested part: swollen stem
- Time of day:
- Harvest in dry weather preferred. Optimal size: fist-sized (approx. 5–8 cm diameter for early varieties, up to 15–20 cm for storage varieties). Over-ripe bulbs become woody and bitter — when ripe, tapping produces a hollow sound (similar to ripe watermelon). Weekly harvest possible: early varieties from May, summer varieties June–August, autumn varieties September–October.
- Drying:
- HARVEST: Cut off close to the ground with a sharp knife. Do not immediately remove the leaves — they protect the bulb from drying out. Remove damaged or wilted leaves. Kohlrabi does NOT regrow (not cut-and-come-again). STORAGE: Early varieties last only a few days to max. 2 weeks (refrigerator, damp cloth, 0–4 °C). Late storage varieties: cellar/sand box at 0–4 °C and 90–95 % humidity, up to several months. Remove leaves before storage.
- Storage:
- 3 months — Early varieties: refrigerator 0–4 °C, 1–2 weeks. Storage varieties: cellar in sand box, 0–4 °C, 90–95 % humidity, several months. Remove leaves. Do not store near apples (ethylene sensitivity).
- Time of day:
- Harvest leaves at the same time as the bulb or pick them earlier. Use only fresh, undamaged young leaves. Very nutritious: approx. twice as much vitamin C as the bulb, approx. 100-fold carotin.
- Drying:
- Use leaves fresh (max. 1–2 days in refrigerator). Do not dry — leaves lose flavour and nutrients quickly. Alternatively blanch briefly (1 minute) and freeze.
- Storage:
- 0.25 months — Leaves fresh: max. 1–2 days in refrigerator, wrapped in damp cloth. Frozen after blanching: up to 12 months.
- Ascorbinsäure (Vitamin C)VitaminContent: ca. 62 mg/100 g (Sprossknolle, roh)Fruit
Exceptionally high vitamin C content for a vegetable — approx. 69–102 % of recommended daily intake per 100 g bulb. In the leaves approx. twice as high. Vitamin C is essential for collagen synthesis, immune function and antioxidant protection. Heat-sensitive — raw consumption or brief steaming maximises content.
- Glucosinolate (Glucoraphanin, Glucoiberin, Glucobrassicin u.a.)GlycosideContent: ca. 4,89 µmol/g Trockengewicht (Gesamtgehalt)Fruit
Sulphur-containing secondary compounds, characteristic of Brassicaceae. In kohlrabi, indolyl glucosinolates (glucobrassicin, neoglucobrassicin) and aliphatic forms (glucoraphanin, glucoiberin) predominate. Myrosinase hydrolyses them on cutting/chewing to isothiocyanates (sulforaphane) and indoles (indole-3-carbinol) — associated with chemoprotective activity in laboratory studies. Goitrogenic in very high amounts.
- KaliumMineralContent: ca. 350–380 mg/100 g (Sprossknolle)Fruit
Well-available potassium source. Potassium is essential for regulation of blood pressure, heart rhythm and neuromuscular excitation conduction. Preparation without prolonged soaking preserves potassium content better.
- KupferMineralContent: ca. 0,13 mg/100 g (ca. 14 % DV)Fruit
Remarkably high copper content for a vegetable. Copper is a cofactor of enzymes in iron metabolism (ceruloplasmin), antioxidant defence (Cu/Zn-SOD) and collagen synthesis (lysyl oxidase). Relevant for immune function and connective tissue integrity.
- Sulforaphan (aus Glucoraphanin)OtherContent: entsteht enzymatisch bei ZellverletzungFruit
Sulforaphane is not a direct plant compound but is formed by myrosinase activation from the glucosinolate glucoraphanin upon cutting or chewing. In laboratory studies, sulforaphane shows phase II enzyme induction (detoxification), antioxidant and anti-inflammatory activity, and inhibition of cancer cell lines. Cooking inactivates myrosinase; raw consumption or light steaming yields higher sulforaphane amounts.
- Ballaststoffe (Cellulose, Pektin, Lignin)PolysaccharideContent: ca. 3,6 g/100 g (Sprossknolle, roh)Fruit
Kohlrabi contains comparatively high dietary fibre for a water-rich vegetable (approx. 91 % water). Insoluble fibres (cellulose, lignin) promote intestinal peristalsis; soluble fibres (pectin) act prebiotically. The outer layer contains woody fibres (lignin) — these are peeled off before consumption.
- Vitamin B6 (Pyridoxin)VitaminContent: ca. 0,15 mg/100 gFruit
Vitamin B6 is a cofactor in amino acid metabolism, neurotransmitter synthesis (serotonin, dopamine, GABA) and haemoglobin synthesis. 100 g kohlrabi covers approx. 11–12 % of daily requirement. Less heat-sensitive than vitamin C.
- Äpfelsäure und Citronensäure (organische Säuren)OtherContent: Hauptträger des charakteristischen GeschmacksFruit
Malic acid and citric acid are the dominant organic acids in kohlrabi and responsible for the mild, slightly sweet-sour flavour of the bulb. They influence mineral bioavailability (chelating agents) and gastric acidity. Both acids are also involved in the citric acid cycle of human metabolism.
- [1]MonographUSDA FoodData Central — Kohlrabi, raw (SR Legacy)(accessed: 2026-05-22)
- [5]MonographKohlrabi Nutrition Facts and Health Benefits — nutrition-and-you.com(accessed: 2026-05-22)
- [6]MonographPlants For A Future (PFAF) — Brassica oleracea database entry(accessed: 2026-05-22)
- [7]MonographCliniTox Giftpflanzen — Brassica oleracea L.: schwach giftig (+) (Institut für Veterinärpharmakologie und -toxikologie, Universität Zürich)(accessed: 2026-08-10)
- [2]WikipediaKohlrabi (Wikipedia EN)(accessed: 2026-05-22)
- [3]WikipediaKohlrabi (Wikipedia DE)(accessed: 2026-05-22)
- [4]WikidataKohlrabi — Wikidata (Q147202)(accessed: 2026-05-22)
🤝 Permaculture Partners
In your garden, this plant acts as:
✨ Best symbiotic partners
Source: Helga und Margarete Langerhorst, Mein gesunder Naturgarten (eigene Kuration)