Radishes: mostly water, and most of the evidence is about other foods

Radish is the rare vegetable whose strongest evidence is about what it does to other things you swallow. A meta-analysis of 23 human dietary trials found that diets rich in cruciferous vegetables raised the activity of the drug-processing enzyme CYP1A2 by 20 to 40 per cent, with radish one of six vegetables pooled into that figure and none of it belonging to radish alone. The authors say what this means in the clinic is still unclear. Swallowed alongside a beta-carotene supplement, oriental radish cut how much of it reached the blood of 10 healthy men to two thirds of the supplement taken by itself. The one trial that gave radish to patients went the wrong way. In 21 people with metabolic syndrome, 14 days of powdered Sakurajima radish left blood vessel function unchanged (p = 0.58) and raised systolic blood pressure by 9.67 mmHg against their usual diet (p = 0.03), in an open-label crossover whose own authors report a carryover effect that limits the primary outcome. That was a concentrated powder of one Japanese cultivar rather than a salad radish. Neither the United States nor the European Union has ever registered a health claim naming radish, in either direction. Both registers are indexed by substance rather than by food, so that zero means nobody ever applied under the name radish, which is not the same as a regulator having said no.

The numbers, per 100 g

How much is actually in it

• Across eight measured samples of raw red radish, folate ranged threefold from 30 to 95 micrograms per 100 g and potassium ranged from 123 to 298 milligrams. — USDA Foundation Foods, Radishes, red, raw, 8 sampled lots, release 2026-04-30 (n = 8 samples) Evidence E source
  Per 100 g across 8 samples: folate 30.48 to 95.24 mcg (mean 63.2, spread 102%), potassium 123 to 298 mg (mean 197.8, spread 88%), sodium 25.5 to 90.2 mg (spread 126%), manganese 0.0248 to 0.119 mg (spread 134%), vitamin C 12.4 to 23.4 mg (mean 17.76, spread 62%), fibre 1.18 to 1.48 g (spread 23%), water 93.46 to 95.44 g (spread 2%)
• The British and American tables differ by 40 per cent on radish folate, but they are not measuring the same vegetable. — USDA Radishes, red, raw against CoFID 2021 entries Radish, white/mooli, raw (13-331) and Radish, red, flesh and skin, raw (13-656) Evidence E source
  Vitamin C 17.76 mg USDA against 24 mg CoFID, a 26 per cent gap; folate 63.2 mcg against 38 mcg, a 40 per cent gap; the automatic pairing chose the white mooli entry, while a red radish entry exists at code 13-656

What a real portion looks like

• Ten weeks of weekly tastings raised how much raw mooli radish preschool children ate from 4.7 g to 17.0 g, and the gain held nine months later. — 219 children aged 2 to 5 years at 11 preschools in England, cluster randomised to taste exposure, nutrition education, both, or nothing; 140 children had complete intake measurements (n = 140 analysed) Evidence B source
  Taste exposure raised intake from 4.7 plus or minus 1.4 g to 17.0 plus or minus 2.0 g, maintained at week 24 and week 36; nutrition education made noneaters more likely to eat some, odds ratio 6.43 (95% CI 1.5 to 27.8); combining both added nothing
• One radish weighs 5 grams, so the per-100-gram figures on any label describe about twenty of them. — USDA FNDDS household measures for Radish (fdc_id 2709803), WWEIA category Other vegetables and combinations Evidence E source
  1 slice 1 g, 1 whole 5 g, 1 cup 115 g, unspecified quantity 58 g

What your body absorbs

• Eating oriental radish at the same time as a beta-carotene supplement cut how much of it reached the blood to two thirds. — 10 healthy men, single ingestion of stir-fried carrot, stir-fried water convolvulus, deep-fried sweet potato ball, purified beta-carotene beadlets, or beadlets together with beta-carotene free oriental radish, serum followed to 32 hours (n = 10) Evidence C source
  Relative bioavailability 65% for beadlets with radish against 100% for beadlets alone, 33% for carrots, 37% for sweet potatoes and 26% for water convolvulus
• How much sulphoraphane reached the blood from a broccoli and daikon radish meal depended on body mass index, moving in opposite directions above and below a BMI of 26. — 18 adults in a randomised crossover feeding study balanced for BMI and GSTM1 genotype, 200 g cooked broccoli with 20 g raw daikon radish daily for 15 days versus a no-broccoli diet (n = 18) Evidence B source
  Above BMI 26 the plasma AUC and urinary excretion of total metabolites were higher on the no-broccoli diet; below BMI 26 they were higher on the daily broccoli diet; GSTM1 genotype made no difference

What cooking and storage change

• Boiling root vegetables in a little water and draining them keeps about 70 per cent of the vitamin C and folate, while the minerals stay almost untouched. — USDA retention factors for the food group Vegetables and Vegetable Products, method VEG,ROOTS,ETC,BLD,DRAIND,LITTLE WTR, retention code 3454 Evidence E source
  Vitamin C and folate retained 70 per cent; thiamin 85 per cent; phosphorus and potassium 90 per cent; calcium, iron, magnesium, sodium, zinc, copper, riboflavin, niacin and vitamin B6 95 per cent; choline and vitamin B12 100 per cent

What it does to your health

• A trigonelline-rich radish eaten for 14 days failed to improve blood vessel function in metabolic syndrome and raised systolic blood pressure by 9.67 mmHg instead. — 21 patients with metabolic syndrome, mean age 59.3 years, multicentre three-period crossover, 14 days each of Sakurajima radish powder, Aokubi radish powder and usual diet with 14-day washouts (n = 21) Evidence B source
  Flow-mediated dilation unchanged versus usual diet (p = 0.58); systolic blood pressure higher by 9.67 mmHg versus usual diet (p = 0.03) and by 8.86 mmHg versus the other radish (p = 0.04); urinary nitric oxide metabolites up (p = 0.03) and oxidative stress marker 8-OHdG up (p = 0.02)
• Four weeks of a Spanish black radish supplement cut unchanged paracetamol in plasma by 40 per cent, which means it shifted how the liver handles the drug. — healthy male volunteers, single-centre open-label pilot, one dietary supplement containing Spanish black radish for 4 weeks, paracetamol metabolites measured at baseline and week 4 (n = not reported in abstract) Evidence C source
  Plasma AUC over 8 hours fell 9% for the glucuronide metabolite (P = 0.004) and 40% for unchanged paracetamol (P = 0.010); urinary sulfate rose 11% (P = 0.010) and mercapturate 37% (P = 0.024); serum estradiol fell 10% (P = 0.005)

Safety, limits and interactions

• Diets rich in cruciferous vegetables, radish among them, raised the activity of the drug-processing enzyme CYP1A2 by 20 to 40 per cent. — 23 dietary intervention trials in humans with drug metabolism end points, vegetables including broccoli, Brussels sprout, cabbage, cauliflower, radish and watercress (n = 23 trials) Evidence A source
  CYP1A2 activity raised 20 to 40 per cent and glutathione S-transferase-alpha raised 15 to 35 per cent by cruciferous vegetable intake
• Adding radish to the diet for a week raised urinary calcium oxalate crystal counts in men and women alike. — 36 subjects, 21 with renal stones and 15 without, early morning urine analysed daily for 14 days, one week of self-selected diet then one week of the same diet with radish (n = 36) Evidence C source
  Calcium oxalate excretion and urinary crystal counts significantly higher on the radish diet in both sexes, with no difference between men and women
• Raw Japanese radish caused pollen food allergy syndrome in a 31 year old man with no allergy history, confirmed by skin prick test. — one 31 year old man with stomatitis and pharyngeal pain after frequently eating raw Japanese radish, Raphanus sativus L. (n = 1) Evidence D source
  Oral and epigastric pain with widespread oral erosion, initially mistaken for herpetic gingivostomatitis; skin prick test confirmed the diagnosis
• Of 180 fresh leafy vegetables sampled in Tehran, 19.4 per cent carried parasites, and radish was the only one free of multiple infections. — 180 fresh leafy vegetable samples of 200 g each, collected across five regions of Tehran in 2020 and 2021, examined by light microscope (n = 180 samples) Evidence C source
  Overall parasitic contamination 19.4 per cent, Trichostrongylus and Toxocara eggs most prevalent at 3.9 per cent, spinach highest at 40 per cent, spring onion none; every vegetable except radish carried multiple parasitic infections

What people believe that the data does not support

• Neither the United States nor the European Union has ever authorised a health claim naming radish. — 21 CFR part 101 health and nutrient content claims (United States, 24 sections, 905 provisions) and the EU Register on nutrition and health claims (snapshot 2026-09-21, 2330 claims) Evidence E source
  Zero mentions of radish in 21 CFR 101; zero claims of any status in the EU register, authorised or rejected

Who this works differently for

• Among 225 people with chronic kidney disease, those eating the most vegetables of the cabbage, radish and onion group had 0.28 times the odds of metabolic acidosis. — 225 adults with non-dialysis-dependent chronic kidney disease at three Tokyo hospitals, median age 72 years, 33.8 per cent women, diet by validated history questionnaire (n = 225) Evidence C source
  Highest versus lowest intake of other vegetables, adjusted odds ratio 0.28 (95% CI 0.10 to 0.79, P = 0.016) for metabolic acidosis; 43 patients (19.1 per cent) had acidosis

The bottom line

Numbers for radish move more than for most foods. Across eight measured lots of raw red radish, folate ranged from 30 to 95 micrograms per 100 g and potassium from 123 to 298 milligrams, while water content stayed between 93.5 and 95.4 g. The variation is in the vegetable, not in the weighing. Sodium ran from 25.5 to 90.2 milligrams over those same eight lots, all bought in the United States, so the spread reflects those growing conditions and not the world. Any single number for radish folate is a mean covering a threefold range. The British table shows 38 micrograms of folate against the American 63.2, a gap of 40 per cent. Most of that comes from the automatic pairing choosing white mooli, which is a different vegetable from a red salad radish, so the gap is a mismatch and not an error in either table. Portions here are small. One radish weighs 5 grams by the United States survey measures and a cup of slices weighs 115 grams, which means every per-100-gram figure you read describes about twenty radishes. Radish is mostly eaten raw, and the only cooking figures available belong to the root vegetable group as a whole: boiled in a little water and drained, roots keep 70 per cent of their vitamin C and folate and 90 to 95 per cent of their minerals. Those factors are for daikon in a soup rather than for a salad. In an 18-person crossover, 20 g of raw daikon was there to supply myrosinase to 200 g of cooked broccoli, and how much sulphoraphane reached the blood then split by body mass index, running higher on the broccoli diet below a BMI of 26 and higher on the no-broccoli diet above it. The radish itself was never the thing being tested. On caution, one week of radish in the diet raised urinary calcium oxalate crystal counts in 36 people, 21 of them with kidney stones. That study was not randomised, its abstract gives no counts and no p-values, and it does not say how much radish anyone ate. Crystals in urine are a step before a stone rather than a stone. A 31 year old man with no allergy history developed widespread oral erosion and throat pain from raw Japanese radish, confirmed by skin prick test, and the report says such cases are few. A concentrated Spanish black radish supplement taken for four weeks cut unchanged paracetamol in plasma by 40 per cent in healthy men. That pilot had no control group, no sample size in its abstract and the supplement maker as sponsor, and it is a reason to keep concentrated supplements away from medicines rather than a finding about salad. Among 225 Japanese adults with chronic kidney disease, those eating the most of a vegetable group holding cabbage, radish and onions had 0.28 times the odds of metabolic acidosis (95% CI 0.10 to 0.79), which is a cross-sectional association across a whole food group and gives radish no figure of its own. Two friendlier notes to end on. Of 180 leafy vegetable samples in Tehran, 19.4 per cent carried parasites and spinach was worst at 40 per cent, while radish was the only vegetable there that did not carry several parasites at once. That is not the same as clean, and washing is what the paper recommends for all of them. And ten weekly tastings raised how much raw mooli preschool children ate from 4.7 g to 17.0 g, a gain still measurable nine months later. Seventeen grams is a taste rather than a portion, and mooli is not the small round radish that the 5 g measure counts.

Sources

1. rdsh-r5-11 · dataset
   Radishes, red, raw [USDA Foundation Foods, release 2026-04-30], 8 samples per 100 g: Folate, total 63.2 UG, range 30.48-95.24; Potassium, K 197.8 MG, range 123.0-298.0; Sodium, Na 51.16 MG, range 25.5-90.2; Manganese, Mn 0.07019 MG, range 0.0248-0.119; Vitamin C, total ascorbic acid 17.76 MG, range 12.4-23.4; Fiber, total dietary 1.314 G, range 1.18-1.48; Water 94.68 G, range 93.46-95.44.
   USDA FoodData Central, Foundation Foods, release 2026-04-30, Radishes, red, raw · checked 2026-09-24
2. rdsh-r5-15 · dataset
   CoFID 2021 (Public Health England, OGL v3.0): Radish, white/mooli, raw [13-331]; Radish, red, flesh and skin, raw [13-656]; Radish leaves, raw [13-332]. Against USDA Radishes, red, raw: vitamin C 17.76 vs 24 mg (26% difference); folate 63.2 vs 38 mcg (40% difference).
   CoFID 2021, Public Health England, OGL v3.0, codes 13-331 and 13-656 · checked 2026-09-24
3. rdsh-r5-09 · cluster randomised trial
   TE increased intake from 4.7±1.4 g to 17.0±2.0 g and this was maintained at both follow-ups. Children assigned to the NE conditions were more likely to eat some of the mooli than children who were not in the NE conditions (odds ratio 6.43, 95% CI 1.5 to 27.8).
   J Acad Nutr Diet, 2019 · checked 2026-09-24
4. rdsh-r5-13 · dataset
   Radish [fdc_id 2709803], FNDDS code 75125000: 1 slice 1 g; 1 whole 5 g; 1 cup 115 g; Quantity not specified 58 g.
   USDA FNDDS, Food and Nutrient Database for Dietary Studies, fdc_id 2709803 · checked 2026-09-24
5. rdsh-r5-05 · human absorption study
   Concurrent ingestion of oriental radish reduced the bioavailability of beadlets to two-thirds of its original value, which partially accounted for the difference between the bioavailability of beadlets and natural foods.
   J Nutr, 2000 · checked 2026-09-24
6. rdsh-r5-06 · randomised crossover trial
   For subjects with BMI >26 kg/m2 (median), plasma AUC and urinary excretion rates of total metabolites were higher on the NB diet than on the DB diet, whereas for subjects with BMI <26 kg/m2, plasma AUC and urinary excretion rates were higher on the DB diet than on the NB diet.
   Br J Nutr, 2018 · checked 2026-09-24
7. rdsh-r5-12 · dataset
   VEG,ROOTS,ETC,BLD,DRAIND,LITTLE WTR [USDA-RETN-R6:3454, Vegetables and Vegetable Products, group 11]: vitamin_c_mg 70%, folate_total_ug 70%, thiamin_mg 85%, phosphorus_mg 90%, potassium_mg 90%, calcium_mg 95%, iron_mg 95%, magnesium_mg 95%, sodium_mg 95%, zinc_mg 95%, copper_mg 95%, riboflavin_mg 95%, niacin_mg 95%, vitamin_b6_mg 95%, choline_mg 100%, vitamin_b12_ug 100%.
   USDA Table of Nutrient Retention Factors, Release 6, 2007, retention code 3454 · checked 2026-09-24
8. rdsh-r5-01 · randomised crossover trial
   Despite successfully stimulating NO production (elevated urinary NOx, p = 0.03), the intervention paradoxically increased oxidative stress (elevated 8-OHdG/creatinine, p = 0.02) and significantly elevated systolic BP compared with the usual diet (+9.67 mmHg, p = 0.03) and Aokubi radish (+8.86 mmHg, p = 0.04).
   Nutrients, 2026 · checked 2026-09-24
9. rdsh-r5-07 · open-label pilot study
   Area under the curve (AUC) from 0 to 8 hours for the acetaminophen glucuronide metabolite and unchanged acetaminophen in plasma decreased from baseline to week 4 by 9% (P = 0.004) and 40% (P = 0.010), respectively.
   BMC Complement Altern Med, 2014 · checked 2026-09-24
10. rdsh-r5-02 · meta-analysis of intervention trials
    The meta-analyses performed demonstrated a significant effect on CYP1A2 and glutathione S-transferase-alpha (GST-α), with consumption of Cruciferae increasing the activities of these enzymes by 20-40% and 15-35%, respectively.
    Clin Pharmacol Ther, 2020 · checked 2026-09-24
11. rdsh-r5-03 · controlled clinical trial
    The study reveals that radish containing diet caused increased excretion of calcium oxalate compared to the self-selected diet and the crystals count in the urine were significantly higher in both genders.
    Nepal Med Coll J, 2004 · checked 2026-09-24
12. rdsh-r5-04 · case report
    He reported frequently consuming raw Japanese radish (Raphans sativus L.) which gave rise to his symptoms. Japanese radish was suspected as the allergen. The skin-prick test confirmed the diagnosis of PFAS.
    Indian J Dermatol, 2023 · checked 2026-09-24
13. rdsh-r5-10 · cross-sectional survey
    The overall rate of parasitic contamination was 19.4%, with Trichostrongylus and Toxocara eggs being the most prevalent parasites (3.9%) and the highest rate of parasitic contamination was observed in spinach (40%), whereas no contamination was found in spring onions. Except for radish, other vegetable samples had multiple parasitic infections.
    Foodborne Pathog Dis, 2025 · checked 2026-09-24
14. rdsh-r5-14 · regulatory register
    EU Register on nutrition and health claims, snapshot 2026-09-21, 2330 claims (262 authorised, 2067 non-authorised, 1 revoked), query radishes: nothing. 21 CFR part 101, query radishes: nothing.
    EU Register on nutrition and health claims, European Commission, snapshot 2026-09-21 · checked 2026-09-24
15. rdsh-r5-08 · cohort baseline analysis
    Greater intake of other vegetables was associated with lower odds of metabolic acidosis (highest vs. lowest intake: adjusted odds ratio = 0.28, 95% confidence interval: 0.10, 0.79, P = 0.016); however, such associations were not observed for other food groups, including potatoes, green/yellow vegetables, and pulses.
    BMC Nephrol, 2026 · checked 2026-09-24