Cabbage and greens: plenty of vitamins, fewer proven effects

In a randomized trial in 231 adults aged 50 to 70 with raised blood pressure, five weeks of leafy greens providing 300 mg nitrate a day did not lower 24-hour systolic pressure. The change was -0.5 mmHg with greens and -0.6 mmHg on placebo. Those were nitrate-rich greens, and cabbage was not tested on its own. In 18 older adults with elevated blood pressure, two weeks of 11 oz (300 g) of cruciferous vegetables a day lowered glycemic variability by 2.0 percent (95% CI -2.8 to -1.1) compared with root vegetables. That was a small trial, a secondary outcome, in people without diabetes, and mean glucose did not change. What cabbage reliably gives is vitamins. Eight USDA samples of raw green cabbage averaged 40.34 mg vitamin C and 59.4 micrograms vitamin K per 3.5 oz (100 g), and a cup is coded at 90 g. Raw spring greens in the UK table carry 180 mg vitamin C and 210 mg calcium per 3.5 oz (100 g).

How much is actually in it

• Eight USDA samples of raw green cabbage averaged 40.34 mg vitamin C and 59.4 micrograms vitamin K per 3.5 oz (100 g), with vitamin K ranging from 41.6 to 82.9. — USDA Foundation Foods, Cabbage, green, raw, 8 samples Evidence E source
  Vitamin C 40.34 mg/100 g (range 34.8-56.3); vitamin K1 59.4 ug/100 g (range 41.6-82.9)
• Raw spring greens in the UK composition table carry 180 mg vitamin C, 210 mg calcium and 92 micrograms folate per 3.5 oz (100 g). — CoFID 2021 record 13-348, Spring greens, raw Evidence E source
  Per 100 g: energy 33 calories, protein 3.0 g, vitamin C 180 mg, calcium 210 mg, folate 92 ug, potassium 370 mg

What a real portion looks like

• In US dietary recall coding a cup of raw green cabbage weighs 3.2 oz (90 g) and a single leaf 25 g. — FNDDS food code 75103000, Cabbage, green, raw (fdc_id 2709773) Evidence E source
  1 cup 90 g; 1 leaf 25 g; 1 head 900 g; quantity not specified 45 g

What your body absorbs

• When 5 men ate 3.5 oz (100 g) of isotope-labeled collard greens with 24 g of fat, blood vitamin K peaked at 6 to 9 hours and was back to baseline by 24 hours. — 5 men (26 to 71 years), single bolus (n = 5) Evidence C source
  Peak 10.51 nmol/L at 6-9 h; baseline 1.26 nmol/L by 24 h; t1/2 22.8 h
• NIH notes the body absorbs only 4% to 17% as much vitamin K from spinach as from a tablet, and eating greens with some fat improves absorption. Evidence E source
  4-17% relative absorption from spinach vs tablet

What cooking and storage change

• By the USDA table for greens boiled in a little water and drained, cooking keeps 60% of vitamin C and 65% of folate but 95% of calcium and iron. — USDA retention factors for Vegetables, VEG, GREENS, BOILED, LITTLE WATER, DRAINED (Retn_Code 3004) Evidence E source
  Vitamin C 60%, folate 65%, thiamin 85%, potassium 90%, calcium 95%, iron 95%, magnesium 95%
• In a randomized crossover trial in 22 healthy adults, five days of cooked Ethiopian kale cut aflatoxin-induced DNA damage in blood cells by 35%, while the raw leaves cut it by 21%. — Twenty-two healthy subjects, five days per arm (n = 22) Evidence B source
  Cooked: DNA damage -35% (+S9) and -33% (-S9), p <= 0.01; raw: -21% (p = 0.08); PGE2 lower after raw
• In a randomized double-blind pilot in 34 IBS patients, six weeks of sauerkraut improved symptom scores by 39 to 57 points whether pasteurized or not. — 34 Norwegian IBS patients, 6 weeks (n = 34) Evidence B source
  IBS-SSS -38.57 (pasteurized) vs -56.99 (unpasteurised), both P < 0.04, no difference between groups
• In a crossover trial in 87 healthy adults, four weeks of daily sauerkraut changed only single gut species, and only the pasteurized version raised serum short-chain fatty acids. — 87 participants, 4 weeks per arm (n = 87) Evidence B source
  SCFA increase only with pasteurized sauerkraut; microbiome largely resilient

What it does to your health

• A dose-response meta-analysis of 226 case-control and cohort studies linked cruciferous vegetable intake with lower cancer risk, an odds ratio of 0.77. — 226 relevant case-control and cohort studies Evidence C source
  OR 0.77; RR 0.96; about 5.4 servings/week for colorectal and lung cancer

Safety, limits and interactions

• A systematic review of 11 studies found no support for cutting vitamin K foods on warfarin-type drugs, with effects on clotting seen only above about 150 micrograms a day. — Two dietary interventional trials and 9 observational studies, patients on VKAs Evidence C source
  Median vitamin K1 intake 76-217 ug/day; effect only >150 ug/day
• A meta-analysis of 23 dietary intervention trials found cruciferous vegetables, cabbage included, raised CYP1A2 drug-metabolizing activity by 20% to 40%. — Twenty-three dietary intervention trials Evidence C source
  CYP1A2 +20-40%; GST-alpha +15-35%
• A systematic review of 123 studies concluded that brassica vegetables in the daily diet, with adequate iodine, pose no adverse effect on thyroid function. — 123 articles of in vitro, animal, and human studies Evidence C source
  No adverse thyroid effect with adequate iodine

What people believe that the data does not support

• In a randomized trial in 231 adults aged 50-70 with raised blood pressure, five weeks of leafy greens with 300 mg nitrate a day did not lower 24-hour systolic pressure. — 243 subjects, 50-70 y old, clinic SBP 130-159 mm Hg; 231 completed; 5 weeks (n = 231) Evidence B source
  Ambulatory SBP change -0.5 mm Hg with leafy greens vs -0.6 placebo; no difference
• The EU refused a claim that cabbage-family vegetables protect cells and DNA and help the body eliminate toxins. — EU Register on nutrition and health claims Evidence E source
  Non-authorized

Who this works differently for

• In a randomized crossover trial in 18 older adults with elevated blood pressure, two weeks of 300 g cruciferous vegetables a day lowered glycemic variability by 2.0% versus root vegetables. — Eighteen participants (female = 89%), median age 68, elevated blood pressure, 2-week arms (n = 18) Evidence B source
  Glycemic variability -2.0% (95% CI -2.8, -1.1); 2-h PPGR -2.5 mg/dL (-4.3 to -0.72; metric: -0.14 mmol/L, -0.24 to -0.04); mean glucose unchanged
• Across three cohorts of 18339 adults aged 45 and over, each extra daily serving of green leafy vegetables was linked with 18% lower dementia risk. — 18,339 participants aged >=45 y, 7-13 y follow-up (n = 18339) Evidence C source
  Pooled HR per serving 0.82 (95% CI 0.70, 0.96)

What is still unknown

• The UK composition table lists raw green cabbage with 48 mg vitamin C and 242 micrograms vitamin K per 3.5 oz (100 g), four times the USDA vitamin K figure. — CoFID 2021 record 13-510, Cabbage, green, raw Evidence E source
  Per 100 g: energy 27 calories, AOAC fiber 4.1 g, vitamin C 48 mg, vitamin K1 242 ug, folate 45 ug, potassium 288 mg

The bottom line

The UK table lists raw green cabbage at 242 micrograms vitamin K per 3.5 oz (100 g), four times the USDA figure, and our sources do not explain the gap. Vitamin K from greens is absorbed poorly. NIH notes the body takes up only 4 to 17 percent as much from spinach as from a tablet, and some fat in the meal helps. In five men who ate 3.5 oz (100 g) of labeled collard greens with 24 g of fat, blood vitamin K peaked at 6 to 9 hours and was back to baseline by 24 hours. By the USDA table for greens boiled in a little water and drained, cooking keeps 60 percent of vitamin C, 65 percent of folate and 95 percent of calcium and iron. In a crossover trial in 22 healthy adults, five days of cooked Ethiopian kale cut aflatoxin-induced DNA damage in blood cells by 35 percent. Raw leaves cut it by 21 percent, which did not reach significance. That was a lab test on blood taken from the volunteers, using Brassica carinata rather than common cabbage. In 34 Norwegian adults with IBS, six weeks of sauerkraut improved symptom scores by 39 points when pasteurized and 57 points when unpasteurised, with no difference between the two and no group without sauerkraut to compare against. In 87 healthy adults, four weeks of daily sauerkraut changed only single gut species, and only the pasteurized version raised short-chain fatty acids in blood. A review of 123 studies found that brassica vegetables in the daily diet, with adequate iodine, did not harm thyroid function. People short of iodine remain the open question. The EU refused a claim that cabbage-family vegetables protect DNA and help the body eliminate toxins. Observational data link more cruciferous vegetables with lower cancer risk (odds ratio 0.77, largely from case-control studies). Three cohorts of 18339 adults aged 45 and over link each extra daily serving of green leafy vegetables with 18 percent lower dementia risk (HR 0.82, 95% CI 0.70 to 0.96). These are associations. If you take warfarin or a similar drug, a review of 11 studies found no support for cutting vitamin K foods, with effects on clotting seen only above about 150 micrograms a day, and the advice that follows is a stable intake. By the UK figure 3.5 oz (100 g) of green cabbage passes that line, and by the USDA figure it does not. In 23 diet trials, cruciferous vegetables raised the activity of CYP1A2, an enzyme that breaks down some drugs, by 20 to 40 percent, with the clinical significance unclear.

Sources

1. cbgr-daily-r6-01 · USDA Foundation Foods dataset
   Cabbage, green, raw: Vitamin C, total ascorbic acid 40.34 MG, range 34.8-56.3 (median 39.65), 8 samples; Vitamin K (phylloquinone) 59.4 UG, range 41.6-82.9 (median 58.2), 8 samples
   USDA FoodData Central, Foundation Foods, release 2026-04-30, Cabbage, green, raw · checked 2026-09-29
2. cbgr-daily-r6-03 · CoFID dataset
   CoFID 13-348 Spring greens, raw: Energy (kcal) 33; Protein (g) 3.0; Vitamin C (mg) 180; Calcium (mg) 210; Folate (µg) 92; Potassium (mg) 370
   CoFID 2021 (Public Health England), code 13-348 · checked 2026-09-29
3. cbgr-daily-r6-04 · FNDDS dataset
   FNDDS 75103000 Cabbage, green, raw: 1 cup 90 g; 1 leaf 25 g; 1 head 900 g; Quantity not specified 45 g
   USDA FNDDS 2021-2023, food code 75103000 · checked 2026-09-29
4. cbgr-daily-r6-11 · clinical trial
   A single bolus of 100 g (396 +/- 28 microg phylloquinone) deuterium-labeled collard greens was fed with a breakfast containing 24 g fat to 5 men (26 to 71 years). ... Plasma total phylloquinone concentrations peaked at 6 to 9 hours (10.51 +/- 4.38 to 8.30 +/- 4.64 nmol/L) and returned to baseline by 24 hours (1.26 +/- 0.38 nmol/L).
   Metabolism, 2004 · checked 2026-09-29
5. cbgr-daily-r6-12 · NIH ODS fact sheet
   For example, the body absorbs only 4% to 17% as much phylloquinone from spinach as from a tablet [2]. Consuming vegetables at the same time as some fat improves phylloquinone absorption from the vegetables, but the amount absorbed is still lower than that from oils.
   NIH Office of Dietary Supplements, Vitamin K Fact Sheet for Health Professionals · checked 2026-09-29
6. cbgr-daily-r6-05 · USDA Table of Nutrient Retention Factors, dataset
   USDA-RETN-R6:3004 VEG,GREENS,BOILD,LITTLE WATER DRAIN: vitamin_c_mg 60%; folate_total_ug 65%; thiamin_mg 85%; potassium_mg 90%; calcium_mg 95%; iron_mg 95%; magnesium_mg 95%
   USDA Table of Nutrient Retention Factors, Release 6, 2007, Retn_Code 3004 · checked 2026-09-29
7. cbgr-daily-r6-06 · RCT
   Cooked B. carinata significantly reduced DNA damage induced by AFB1 as compared to baseline levels (+S9 mix: 35%, -S9 mix: 33%, p ≤ 0.01, respectively). Raw B. carinata only reduced DNA damage by S9-activated AFB1 by 21% (p = 0.08).
   Nutrients, 2018 · checked 2026-09-29
8. cbgr-daily-r6-09 · RCT
   The mean change in IBS-SSS was -38.57 ± 17.08 PS vs. -56.99 ± 16.92 UPS and was significantly improved in both groups (P < 0.04), while the improvement in symptoms was not different between the intervention groups.
   Food Funct, 2018 · checked 2026-09-29
9. cbgr-daily-r6-10 · RCT
   Only pasteurized sauerkraut consumption increased serum short-chain fatty acids (SCFAs). CONCLUSIONS: The gut microbiome of healthy individuals is rather resilient to short-term dietary interventions even though single species might be affected by sauerkraut consumption.
   Microbiome, 2025 · checked 2026-09-29
10. cbgr-daily-r6-16 · systematic review and meta-analysis
    Intake of cruciferous vegetables can prevent cancers, with an odds ratio of 0.77 and risk ratio (RR) of 0.96.
    Nutr Rev, 2025 · checked 2026-09-29
11. cbgr-daily-r6-13 · systematic review
    Median dietary intake of vitamin K1 ranged from 76 to 217 μg/day among studies, and an effect on coagulation may be detected only for high amount of vitamin intake (>150 μg/day). ... The available evidence does not support current advice to modify dietary habits when starting therapy with VKAs.
    Medicine (Baltimore), 2016 · checked 2026-09-29
12. cbgr-daily-r6-14 · systematic review and meta-analysis
    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 2026-09-29
13. cbgr-daily-r6-15 · systematic review
    The vast majority of the results cast doubt on previous assumptions claiming that brassica plants have antithyroid effects in humans. Instead, they indicate that including brassica vegetables in the daily diet, particularly when accompanied by adequate iodine intake, poses no adverse effects on thyroid function.
    Int J Mol Sci, 2024 · checked 2026-09-29
14. cbgr-daily-r6-08 · RCT
    The insignificant change in ambulatory SBP (mean ± standard deviation) was -0.6 ± 6.2 mm Hg in the placebo group, -1.2 ± 6.8 mm Hg in the potassium nitrate group, and -0.5 ± 6.6 mm Hg in the leafy green vegetable group. There was no significant difference in change between the 3 groups.
    Am J Clin Nutr, 2020 · checked 2026-09-29
15. cbgr-daily-r6-18 · EU claims register
    POL-HC-6819 Brassicaceae (Cruciferae) (Common Name : Botanical family that include broccoli, couliflower, cabbage, Bruxelles sprouts etc.) Are particularly rich of protective compounds that protect cells and DNA from oxidative damage/are particularly rich of compounds that help our body to eliminate toxic substances Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-6819, snapshot 2026-09-21 · checked 2026-09-29
16. cbgr-daily-r6-07 · RCT
    Glycaemic variability was lower in the active versus control (mean difference: -2.0%, 95% CI -2.8, -1.1, p < 0.001). Overall PPGR 2-h and AUC were lower in the active versus control (mean difference: -0.14 mmol/L, 95% CI -0.24, -0.04, p = 0.005 and -20.1 mmol/L × min, 95% CI -34.1, -6.1, p = 0.005, respectively), driven by the dinner PPGR (p = 0.004 and p = 0.003, respectively).
    Diabetes Obes Metab, 2025 · checked 2026-09-29
17. cbgr-daily-r6-17 · cohort
    Additionally, green leafy vegetables demonstrated a protective association (pooled HR per serving increment: 0.82; 95% CI: 0.70, 0.96, P-trend = 0.015).
    Am J Clin Nutr, 2026 · checked 2026-09-29
18. cbgr-daily-r6-02 · CoFID dataset
    CoFID 13-510 Cabbage, green, raw: Energy (kcal) 27; AOAC fibre (g) 4.1; Vitamin C (mg) 48; Vitamin K1 (µg) 242.00; Folate (µg) 45; Potassium (mg) 288
    CoFID 2021 (Public Health England), code 13-510 · checked 2026-09-29