Black radish: are its benefits for the liver proven?

Search for “black radish benefits” online and the same promise often appears: this large winter radish supposedly “drains” the liver and “detoxifies” the body. Black radish is primarily a very low-calorie vegetable, rich in pungent sulphur compounds. Its effect on the human liver has only been measured in one small trial. Here is what it provides, what studies actually show, how to eat it and the precautions to know.

What is black radish?

Black radish (Raphanus sativus var. niger) belongs to the cruciferous family, like cabbage, broccoli and mustard. It is a winter radish: traditional varieties include the round black winter radish and the long black winter radish of Paris. Beneath its black skin is firm, white, pungent flesh.

It can be eaten raw or cooked, but is also available as juice, in drinkable ampoules or in capsules. In France, its root is included in the official list of plants permitted in food supplements. For example, it is part of the Hexagon® Detox complex, alongside artichoke, milk thistle and NAC.

What does black radish contain?

It is a water-rich, low-calorie vegetable: 28.2 kcal per 100 g. According to the ANSES Ciqual database, 100 g of raw black radish provides 300mg of potassium, or 15% of the nutrient reference value, and 9.58mg of vitamin C, around 12%. Compared with small red radishes, it contains more potassium and calcium, but less vitamin C and folate.

Why is black radish pungent?

Its pungency comes from sulphur compounds. Like all cruciferous vegetables, black radish contains glucosinolates, and one of them, glucoraphasatin, accounts for more than 65% of the total. In the intact root, these molecules are kept separate from an enzyme called myrosinase.

When the radish is cut, grated or chewed, the two meet. Myrosinase then converts glucoraphasatin into an isothiocyanate, raphasatin, with a pungent and sometimes irritating taste. This compound is very unstable: in water, its half-life is no more than 30 minutes. Heat inactivates myrosinase.

Does black radish really cleanse the liver?

There is no evidence that it does. Its reputation comes from tradition: the root has been used since antiquity to stimulate biliary function. Herbal medicine classifies it among choleretic plants, supposed to increase bile production by the liver, and cholagogues, supposed to facilitate bile release from the gallbladder.

But stimulating bile is not the same as “cleansing” the liver. This organ continuously transforms and eliminates unwanted substances without needing outside assistance, as we explain in our article liver detox: myth or reality.

“Drain”, “detoxify” and “depurative”: none of these terms corresponds to an authorised claim, and no health claim is authorised for black radish in the European Union. The only one mentioning the liver concerns a nutrient, choline: “Choline contributes to the maintenance of normal liver function”, for a product providing at least 82.5mg per 100 g, 100 ml or portion.

Black radish benefits: what do studies show?

Most evidence comes from laboratory and animal studies. Only one human study has been published.

In the laboratory: activation of liver enzymes

In laboratory-grown human liver cancer cells (the HepG2 cell line), an aqueous black radish extract stimulated “phase I” and “phase II” enzymes, which transform and then neutralise foreign substances. Glucoraphasatin alone had no effect: its isothiocyanate triggered the response at 10 µM. A second study by the same team showed that raphasatin was more active than its breakdown products. Both studies came from the research department of the manufacturer that funded the human trial described below.

In animals: effects at high doses

In mice, two weeks of a diet containing 20% freeze-dried radish, an amount far beyond a portion of vegetables, increased the expression of several liver enzymes. Other research points in the same direction:

• in mice fed a diet designed to produce cholesterol stones, 6 days of black radish juice eliminated the stones, but not gallbladder inflammation (6 mice per group);
• in rats fed a diet high in fat and cholesterol, the juice improved markers of oxidative stress;
• in mice with experimentally induced fatty liver, fermented black radish (50 to 400mg/kg per day for 2 weeks) reduced liver transaminases, inflammation and fibrosis.

These results justify further research, not conclusions. The doses, extracts and animal models remain very different from human consumption.

In humans: just one pilot trial

In Canada in 2011, 20 healthy men aged 25 to 35 took 6 tablets per day for 4 weeks. Each tablet contained 370mg of black radish, with a little acerola and camu camu, and there was no placebo group. Before and after the intervention, they received 1 g of paracetamol to track its fate in the body.

• Unchanged paracetamol in the blood decreased by 40%.
• Urinary mercapturates, produced through the glutathione pathway, increased by 37%.
• Transaminases did not change, and all tests remained normal.

The authors interpreted this as stimulation of liver enzymes. But the study was small, had no placebo, was funded by the supplement manufacturer and measured no clinical benefit. One participant reported mild indigestion, possibly related to the product.

How should black radish be eaten?

Raw and grated, it retains its sulphur compounds: myrosinase remains active and releases isothiocyanates when it is cut. It is best grated just before serving, since raphasatin breaks down quickly. Cooked radish is milder because heat inactivates the enzyme. For broccoli, a close relative, a trial in 8 men measured absorption of its isothiocyanate, sulforaphane, at 37% when raw compared with 3.4% when cooked.

• Peeled or unpeeled? The skin can be eaten if thoroughly scrubbed. In radishes, myrosinase is found particularly in the outer layer of the root: keeping the skin preserves some of the enzyme.
• As juice: no human trial has assessed its effects or tolerability. If you drink it, start with a small amount.
• How much? A normal vegetable portion. An adult serving is 80 to 100 g, roughly a handful of small red radishes. No amount has been validated for an effect on the liver.

What precautions apply to black radish?

Its pungency can irritate a sensitive stomach: start with small amounts as part of a meal. The main precautions concern juices and concentrated extracts.

Gallstones and bile duct obstruction

This is the classic contraindication for plants reputed to stimulate bile. For artichoke, another plant considered choleretic, the European Medicines Agency lists bile duct obstruction, cholangitis, liver disease and gallstones as contraindications. The same caution applies to black radish, traditionally used to stimulate bile.

The mouse findings do not change this rule: no human trial has reproduced them. Pain beneath the ribs on the right, fever or jaundice require prompt medical advice.

Black radish and the thyroid

The concern relates to cruciferous vegetables generally: at high doses, some derivatives of their glucosinolates can interfere with thyroid function. In rats whose diet consisted of one-third fresh or cooked radish for 90 days, TSH increased by 210 to 286% and thyroid hormones decreased, even with iodine intake. In humans, the only available study, using red radish sprouts in women with obesity, showed no significant change in TSH.

A 2024 systematic review of 123 publications concluded that cruciferous vegetables consumed regularly with sufficient iodine intake do not harm the thyroid. Nothing in human evidence justifies excluding this vegetable in hypothyroidism. Juices and extracts have not been assessed: discuss them with your doctor. Iodine's role is explained in our article on iodine deficiency and the thyroid.

Medicines: caution with extracts

The pilot trial suggests that a black radish supplement can change how the body processes paracetamol. The consequences for other medicines have not been studied. If you take medication, seek advice from your doctor or pharmacist before taking drinkable ampoules or capsules. As for vitamin K, monitored with vitamin K antagonist anticoagulants, the root contains very little: less than 0.8 µg per 100 g.

Frequently asked questions

Does black radish help with weight loss?

No human study has shown this. However, it is very low in calories and can replace richer side dishes. No food causes weight loss on its own.

Does black radish lower gamma-GT?

In the pilot trial, the 20 volunteers' gamma-GT decreased on average after 4 weeks, while remaining within normal ranges. This says nothing about effects in someone with elevated gamma-GT. A high level may reflect alcohol consumption, medication or liver disease and must be interpreted by a doctor.

Are black radish ampoules and capsules effective?

None has been assessed for a health benefit. Their black radish content varies between products, and they often combine it with other plants such as artichoke or milk thistle, whose trials we have critically examined. Read the label and be wary of “drainage” promises.

Does black radish syrup relieve a cough?

It is a widespread traditional home remedy, but no published clinical trial has evaluated it. A persistent cough, or one accompanied by fever, breathlessness or coughing up blood, warrants medical advice.

Can you eat black radish every day?

As a vegetable, there is no reason a healthy person cannot, while varying it with other vegetables. Daily juice or extract use has not been assessed over the long term.

Is black radish discouraged during pregnancy?

Thoroughly washed, raw or cooked black radish can be part of a varied diet. Juices, drinkable ampoules and extracts, however, have not been studied during pregnancy or breastfeeding: it is best to avoid them without medical advice.

Conclusion

Black radish's benefits are primarily those of a winter vegetable: very few calories, plenty of water, potassium and sulphur compounds that give it its pungency. Its reputation as a liver “cleanser” rests on tradition and cell and animal studies. In humans, only one pilot trial without a placebo observed changes in paracetamol elimination, with no measured benefit.

Grated raw just before eating, it retains most of its compounds. Avoid juices and extracts if you have gallstones, and seek advice if you take medication.

Sources

1. ANSES (2025). Ciqual food composition database: raw black radish (code 20089) and raw red radish (code 20045). ciqual.anses.fr
2. Hanlon PR, Webber DM, Barnes DM (2007). Aqueous extract from Spanish black radish (Raphanus sativus L. Var. niger) induces detoxification enzymes in the HepG2 human hepatoma cell line. Journal of Agricultural and Food Chemistry, 55(16), 6439-6446. doi:10.1021/jf070530f
3. Scholl C, Eshelman BD, Barnes DM, Hanlon PR (2011). Raphasatin is a more potent inducer of the detoxification enzymes than its degradation products. Journal of Food Science, 76(3), C504-C511. doi:10.1111/j.1750-3841.2011.02078.x
4. Ishida M et al. (2014). Glucosinolate metabolism, functionality and breeding for the improvement of Brassicaceae vegetables. Breeding Science, 64(1), 48-59. doi:10.1270/jsbbs.64.48
5. Lugasi A et al. (2005). Antioxidant effect of squeezed juice from black radish (Raphanus sativus L. var niger) in alimentary hyperlipidaemia in rats. Phytotherapy Research, 19(7), 587-591. doi:10.1002/ptr.1655
6. Castro-Torres IG et al. (2012). Antilithiasic and hypolipidaemic effects of Raphanus sativus L. var. niger on mice fed with a lithogenic diet. Journal of Biomedicine and Biotechnology, 2012, 161205. doi:10.1155/2012/161205
7. Ahn M et al. (2019). Fermented black radish (Raphanus sativus L. var. niger) attenuates methionine and choline deficient diet-induced nonalcoholic fatty liver disease in mice. Food Science & Nutrition, 7(10), 3327-3337. doi:10.1002/fsn3.1200
8. Evans M, Paterson E, Barnes DM (2014). An open label pilot study to evaluate the efficacy of Spanish black radish on the induction of phase I and phase II enzymes in healthy male subjects. BMC Complementary and Alternative Medicine, 14, 475. doi:10.1186/1472-6882-14-475
9. Vermeulen M et al. (2008). Bioavailability and kinetics of sulforaphane in humans after consumption of cooked versus raw broccoli. Journal of Agricultural and Food Chemistry, 56(22), 10505-10509. doi:10.1021/jf801989e
10. Galanty A et al. (2024). Do Brassica Vegetables Affect Thyroid Function? A Comprehensive Systematic Review. International Journal of Molecular Sciences, 25(7), 3988. doi:10.3390/ijms25073988
11. European Medicines Agency (2018). European Union herbal monograph on Cynara cardunculus L. (syn. Cynara scolymus L.), folium (EMA/HMPC/194014/2017). ema.europa.eu
12. Ministry of the Economy (2014). Order of 24 June 2014 establishing the list of plants, other than fungi, permitted in food supplements and the conditions of their use. Official Journal of the French Republic. legifrance.gouv.fr
13. European Commission (2012). Regulation (EU) No 432/2012 of 16 May 2012 establishing a list of permitted health claims made on foods, other than those referring to the reduction of disease risk and to children's development and health. Official Journal of the European Union, L 136, p. 1 (consolidated version). eur-lex.europa.eu
14. Santé publique France (2023). Fruit and vegetables: at least 5 a day. Manger Bouger, on Santé.fr. sante.fr

Food supplements do not replace a varied, balanced diet or a healthy lifestyle. Ask a healthcare professional for advice if you are taking medication, pregnant or breastfeeding.