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Radish
CautionRadieschen · (Raphanus sativus var. sativus)
Cabbage family (Brassicaceae)
Description
The radish is the fastest root in the garden: ready to pull four to six weeks after sowing, which makes it a useful filler between slower crops. The round to oval root is red, white or two-toned outside and white and crisp within. Its bite comes from glucosinolates that break down into isothiocyanates when the root is cut; how sharp it turns out depends heavily on variety, watering and warmth — drought and heat make it hotter and woodier. Beyond vitamin C and potassium it supplies almost no calories. The leafy tops are edible too and can be turned into soup or pesto, though they usually end up in the bin. Traditionally, like other radishes, it counts as a stimulant to digestion.
The radish is one of the fastest-growing vegetables (harvest after approx. 25–35 days) and is consumed fresh worldwide. The root contains approx. 27–29 mg vitamin C per 100 g (approx. 30 % of daily requirement), potassium (approx. 225–255 mg/100 g), folate and iron (approx. 1.2 mg/100 g) at only 14 kcal/100 g. Eaten raw in salads, as a snack with butter and sea salt (classic French style), in dips or thinly sliced on open sandwiches. The sharp flavour comes from isothiocyanates (especially 4-methylthio-3-butenyl isothiocyanate / glucoraphasatin degradation product), released from glucosinolates by myrosinase upon cell damage.
In the traditional folk medicine of Europe and Asia, radishes are considered digestive-promoting, appetite-stimulating and mildly laxative. The bitter compounds and mustard oils (isothiocyanates) are believed to stimulate bile secretion and promote liver circulation. Folk-medicinal tradition sees grated or pressed radishes as a traditional remedy for bloating, sluggish digestion and flatulence. PFAF references the tonic and laxative effect on the intestines and indirect gallbladder stimulation.
Fresh radish juice or grated radishes were used in folk medicine for colds, coughs and bronchitis. The antibacterially active substance raphanin (a glucosinolate breakdown product with isothiocyanate-like structure) is said to be expectorant and germicidal. PFAF mentions the use of seeds for digestive complaints and bronchitis. Clinical evidence is lacking; folk-medicinal tradition from several European and Asian traditions.
Radish leaves are as edible as the root: they contain (dried) extremely high levels of vitamin C (approx. 704 mg/100 g dry), calcium (approx. 1,913 mg/100 g dry), iron and potassium according to PFAF. Fresh leaves can be sautéed as leafy greens, used in salads or added to soups. In normal households they are usually discarded — an underrated nutrient supplier. Young leaves are milder, older ones somewhat bitter.
Grated or mashed radish root was used in folk medicine as an external compress for minor burns, bruises and skin irritation (PFAF). The cooling, moist mass is said to soothe local inflammatory reactions. Not clinically confirmed; no substitute for medical wound care. Isothiocyanates can cause irritation on sensitive skin — observe short application time.
Sources: [3]
Radishes contain glucosinolates (especially glucoraphasatin, glucoraphenin, glucoerucin) and their breakdown products isothiocyanates (especially sulforaphene, sulforaphane). Sulforaphane activates the transcription factor Nrf2, which induces cellular detoxification enzymes. Preclinical studies (in vitro / animal model) show antiproliferative and antioxidative effects. Anthocyanins (pelargonidin in red radish) act antioxidatively and may inhibit LDL oxidation. Clinical evidence in humans is still outstanding.
Radish seeds contain particularly high concentrations of glucosinolates and isothiocyanates and are used in folk medicine to promote digestion and as an appetite-stimulating spice. Sprouts from radish seeds (microgreens) are a concentrated source of glucosinolates, flavonoids, beta-carotene and vitamin C. PFAF mentions the use of seeds for indigestion, flatulence and bronchitis.
Radishes well tolerated in normal amounts. Contains glucosinolates / isothiocyanates (mustard oils): with gastric ulcers, duodenal ulcers or severe gastritis increased mucosal irritation possible — in these cases consume in moderation or avoid. Very large amounts of radishes may be relevant in thyroid conditions (goitrogenic effect of glucosinolates — inhibit iodine uptake at high doses). Maintain moderate consumption with hypothyroidism.
Radishes as food are considered safe in normal amounts during pregnancy. Valuable source of vitamin C, folate and iron. Avoid large amounts of radishes or concentrated radish extracts as a precaution.
Radishes in normal amounts are considered safe during lactation.
Radishes are suitable from weaning age (approx. 8–10 months) — in small grated pieces. The sharp flavour may require acclimatisation for young children. From approx. 1 year also as finger food in small slices.
Drug interactions
Schilddrüsenhormone (Levothyroxin)
Glucosinolates in very large amounts can inhibit iodine uptake into the thyroid (goitrogenic effect) and thereby influence the effect of thyroid hormone replacement therapies. Clinically not relevant at normal consumption amounts.
Contraindications
- Severe gastritis, gastric or duodenal ulcers — isothiocyanates (mustard oils) can irritate the mucosa; avoid radishes or consult a physician.
- Known allergy to Brassicaceae (crucifers) — cross-reaction with other mustard-oil plants possible.
Harvested part: root (fresh)
- Time of day:
- Harvest when the root has reached approx. 2–3 cm diameter (after approx. 25–35 days depending on variety and temperature). Do not harvest too late: overripe radishes become spongy, woody or hollow inside and lose flavour and crunch. Time of day: harvest in the morning or evening in cool weather — radishes bolt faster in heat.
- Drying:
- STORAGE: Separate radishes from their leaves immediately after harvesting (leaves draw moisture from the root). Wrap in a damp cloth or damp paper and store in the vegetable drawer of the refrigerator. Shelf life: approx. 5–7 days. Do not store near apples or bananas (ethylene accelerates maturation and bitterness). Store leaves separately and use quickly (1–2 days).
- Storage:
- 0.25 months — Refrigerator, vegetable drawer (2–5 °C), without leaves, in a damp cloth. Only keeps a few days — harvest fresh and consume promptly.
- Time of day:
- Cut leaves together with the root at harvest. Young leaves (shortly after germination, as microgreens) are particularly tender and nutrient-dense. Older leaves become coarser and more bitter — still usable, but better sautéed than raw. Microgreens (5–7 days after germination) for most intense nutrient content.
- Drying:
- Radish leaves are not storable — use immediately or keep in the refrigerator for only 1–2 days in a damp cloth. Dried they lose most vitamins. Not suitable for tea.
- Glucoraphasatin (Dehydroerucin-Glucosinolat)GlycosideContent: 0,05–0,3 % (Frischgewicht Wurzel)Root
The main glucosinolate of radish. Converted by myrosinase activity upon cell damage to the isothiocyanate 4-methylthio-3-butenyl isothiocyanate (sulforaphene analogue) — primary source of the sharp flavour. Seeds and sprouts contain even higher concentrations.
- RaphaninOtherContent: SpurenRoot
Glucosinolate breakdown product with antibacterial and antifungal properties (PFAF). Structurally related to isothiocyanates. Not investigated in clinical studies; regarded in folk medicine as the germicidal principle of radish juice.
- Pelargonidin (Anthocyan)FlavonoidContent: Spuren–0,02 % (rote Schale)Root
Responsible for the characteristic red colour of radish roots. Pelargonidin is an anthocyanidin with antioxidant properties. Preclinical: inhibits LDL oxidation and shows anti-inflammatory activity. Red radishes contain more anthocyanins than white varieties.
- Ascorbinsäure (Vitamin C)VitaminContent: ca. 27–29 mg/100 gRoot
Remarkably high vitamin C content for a water-rich vegetable (95 % water): 100 g of radishes provide approx. 30 % of the recommended daily intake (EU: 80 mg). Vitamin C is antioxidant, immune-enhancing and promotes collagen synthesis. Best preserved when consumed raw — heating significantly reduces content.
- KaliumMineralContent: ca. 225–255 mg/100 gRoot
Important macronutrient for cardiac rhythm, blood pressure regulation and muscle contraction. Radishes provide a relevant contribution to potassium supply at very low caloric content (14 kcal/100 g).
- EisenMineralContent: ca. 1,2 mg/100 gRoot
Noteworthy iron content for a vegetable with 95 % water content. Non-haem iron is better absorbed when consumed with vitamin C simultaneously — a natural synergism in raw radish. Leaves contain considerably more iron than the root.
- MyrosinaseOtherContent: Enzym (kein Prozentwert)Whole plant
Thioglucosidase that hydrolyses glucosinolates to isothiocyanates, nitriles and other breakdown products upon cell damage (chewing, cutting). Myrosinase is heat-inactivated — cooking inactivates the enzyme so that glucosinolates are not converted to isothiocyanates. Raw radishes are therefore more bioactive than cooked ones.
- Folsäure (Vitamin B9)VitaminContent: ca. 25 µg/100 gRoot
Moderate folate source; contributes to meeting daily requirements (reference value adults: 300 µg/day). Essential for DNA synthesis and cell division. Particularly relevant in early pregnancy.
- [3]MonographPlants For A Future (PFAF) — Raphanus sativus database entry(accessed: 2026-05-22)
- [4]MonographFrontiers in Nutrition — Glucosinolate extract from radish (Raphanus sativus L.) seed attenuates high-fat diet-induced obesity (2024)(accessed: 2026-05-22)
- [1]WikipediaRadieschen (Wikipedia DE)(accessed: 2026-05-22)
- [2]WikipediaRadish (Wikipedia EN)(accessed: 2026-05-22)
🤝 Permaculture Partners
In your garden, this plant acts as:
✨ Best symbiotic partners
📦 Part of these planting sets:
Source: Helga und Margarete Langerhorst, Mein gesunder Naturgarten (eigene Kuration)