Cabbage and collard greens: one family, very different numbers

Across 23 dietary intervention trials, eating cruciferous vegetables, cabbage among them, raised the activity of the drug-handling enzyme CYP1A2 by 20 to 40 percent and of GST-alpha by 15 to 35 percent. The authors call the clinical meaning unclear, and collards were not among the vegetables tested. As foods the two greens are far apart. In USDA lab samples, 8 of each, raw collards carry about 276 mg of calcium per 3.5 oz (100 g) against about 42 mg in raw green cabbage, and the ranges do not overlap. Raw collards also hold about 89 mg of vitamin C per 3.5 oz (100 g) against about 40 mg. The widest gap is vitamin K: a cup of cooked collards gives about 618 micrograms and a cup of raw green cabbage about 54, both scaled from 100 g values.

How much is actually in it

• Raw collards carry about 276 mg of calcium per 3.5 oz (100 g) against about 42 mg in raw green cabbage, roughly six times more, in USDA lab samples. — USDA Foundation Foods samples, Collards raw and Cabbage green raw, 8 samples each (n = 8 + 8 samples) Evidence E source
  Calcium collards 276.4 mg (range 170-340) vs green cabbage 41.84 mg (range 23.1-64.1) per 3.5 oz (100 g)
• Raw collards hold about 89 mg of vitamin C per 3.5 oz (100 g) against about 40 mg in raw green cabbage, with collards ranging from 64 to 111 mg across samples. — USDA Foundation Foods samples, 8 per food (n = 8 + 8 samples) Evidence E source
  Vitamin C collards 89.4 mg (64-111) vs green cabbage 40.34 mg (34.8-56.3) per 3.5 oz (100 g); red cabbage 53.88 mg

What a real portion looks like

• One cup of cooked collards gives about 618 micrograms of vitamin K, while one cup of raw green cabbage gives about 54. — US survey food portions, FNDDS (n = 3 food codes) Evidence E source
  Vitamin K per cup: collards cooked with oil 618.4 microg (135 g), collards raw 157.4 microg (36 g), green cabbage raw 53.5 microg (90 g)

What your body absorbs

• In 5 men eating 3.5 oz (100 g) of labeled collard greens with a 24 g fat breakfast, plasma vitamin K peaked at 6 to 9 hours and returned to baseline within 24 hours. — 5 men aged 26-71, single 3.5 oz (100 g) serving with 24 g fat (n = 5) Evidence C source
  Peak 10.51 +/- 4.38 nmol/L at 6-9 h, baseline 1.26 nmol/L by 24 h
• In a crossover trial of 25 people eating 1.8 oz (50 g) a day of raw vegetable for 3 days, a low-glucobrassicin cabbage produced less urinary DIM than Brussels sprouts by 8.73 pmol/mg creatinine. — 25 subjects, 50 g raw vegetable daily for 3 days, crossover (n = 25) Evidence B source
  Difference 8.73 pmol/mg creatinine (95% CI 5.36-12.10), P = 0.00002
• In 45 people fed Brussels sprouts and cabbage at seven glucobrassicin doses, urinary DIM rose with dose and plateaued between 200 and 300 micromol. — 45 subjects, vegetables once daily for 2 days at 25-500 micromol glucobrassicin (n = 45) Evidence B source
  R2 = 0.68 dose vs urinary DIM; plateau 200-300 micromol

What cooking and storage change

• By the USDA retention table for vegetables boiled in water and drained, greens keep about 55% of vitamin C and 60% of folate but 95% of calcium. — USDA retention factors for the group Vegetables and Vegetable Products (n = -) Evidence E source
  Boiled, water to cover, drained: vitamin C 55%, folate 60%, thiamin 80%, potassium 85%, calcium 95% retained
• UK food tables give raw green cabbage 48 mg of vitamin C per 3.5 oz (100 g) and boiled green cabbage 45 mg, a second number close to the USDA raw figure. — CoFID items Cabbage green raw and boiled in unsalted water (n = 2 items) Evidence E source
  Vitamin C 48 mg raw vs 45 mg boiled; calcium 56 vs 54 mg per 3.5 oz (100 g)

What it does to your health

• Observational data from 22 studies link high cruciferous vegetable intake, including cabbage, with a lower gastric cancer risk (RR 0.81, 95% CI 0.75-0.88). — 16 case-control and 6 prospective studies (n = 22 studies) Evidence C source
  RR 0.81 (95% CI 0.75-0.88); cabbage alone similar; prospective studies borderline

Safety, limits and interactions

• Among 17 patients allergic to cabbage, 5 reported anaphylaxis, and the main allergen Bra o 3 cross-reacted with mugwort pollen and peach. — 17 patients allergic to cabbage, Spain (n = 17) Evidence C source
  5 of 17 anaphylaxis; Bra o 3 skin test positive in 12 of 14 (86%)

What people believe that the data does not support

• According to the NIH calcium fact sheet, collard greens are among foods high in oxalic acid, while calcium from cabbage is absorbed about as well as from milk, though with much less calcium per serving. — general population (n = -) Evidence E source
  No number for collards; spinach 5% vs milk 27% absorption given as contrast
• The EU did not authorize the claim that cabbage-family vegetables protect cells and DNA from oxidative damage or help the body remove toxins. — EU food labeling (n = -) Evidence E source
  Non-authorized

Who this works differently for

• According to NIH, people taking warfarin and similar anticoagulants should keep their vitamin K intake from food and supplements consistent, because sudden changes can raise or lower the anticoagulant effect. — people taking warfarin and similar anticoagulants (n = -) Evidence E source
  Sudden intake changes can raise or lower anticoagulant effect
• Across 23 dietary intervention trials including cabbage, eating cruciferous vegetables raised CYP1A2 activity by 20-40% and GST-alpha activity by 15-35%. — 23 dietary intervention trials in humans, broccoli, Brussels sprout, cabbage, cauliflower, radish, watercress (n = 23 trials) Evidence B source
  CYP1A2 +20-40%, GST-alpha +15-35%

The bottom line

More calcium in the food does not tell you how much reaches your blood. The NIH calcium fact sheet lists collard greens among foods high in oxalic acid and says calcium from cabbage is absorbed about as well as from milk, with much less of it per serving. We found no study measuring calcium absorption from collards. By a USDA group factor dated 1975, greens boiled in water and drained keep about 95% of their calcium, 60% of folate and 55% of vitamin C. UK tables put boiled green cabbage at 45 mg of vitamin C per 3.5 oz (100 g) against 48 mg raw, counted on cooked weight. We found no measurement of how much vitamin K cooking removes. Observational data from 22 studies, 16 of them case-control, link high cruciferous intake with lower gastric cancer risk (RR 0.81, 95% CI 0.75 to 0.88), and cabbage alone gave a similar result. Case-control designs carry recall bias, and this is an association. The EU did not authorize the claim that this vegetable family protects cells from oxidative damage or helps the body remove toxins. Who should be careful. If you take warfarin, NIH says to keep vitamin K intake steady, because sudden changes can raise or lower the drug's effect, and collards carry far more vitamin K per cup than cabbage. The enzyme rise above involves a drug-handling enzyme, was measured as enzyme activity rather than drug levels, and its authors call the clinical meaning unclear. Cabbage allergy is rare and can be serious: among 17 allergic patients seen in Spain, 5 reported anaphylaxis, and the main allergen cross-reacted with mugwort pollen and peach.

Sources

1. cbcl-r4-01 · USDA FoodData Central Foundation Foods, dataset
   Collards, raw: Calcium 276.4 mg per 100 g, range 170.0-340.0 (median 293.0), 8 samples; Cabbage, green, raw: Calcium 41.84 mg, range 23.1-64.1 (median 39.4), 8 samples
   USDA FoodData Central, Foundation Foods, release 2026-04-30 (Collards raw FDC 2685574; Cabbage green raw) · checked 2026-10-01
2. cbcl-r4-02 · USDA FoodData Central Foundation Foods, dataset
   Collards, raw: Vitamin C 89.4 mg per 100 g, range 64.0-111.0 (median 87.0), 8 samples; Cabbage, green, raw: Vitamin C 40.34 mg, range 34.8-56.3 (median 39.65), 8 samples; Cabbage, red, raw: 53.88 mg, range 45.4-71.4
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-10-01
3. cbcl-r4-03 · USDA FNDDS 2021-2023, dataset
   Collards, fresh, cooked with oil (FDC 2709582): vitamin K 458.1 ug per 100 g, 1 cup 135 g = 618.4 ug; Collards, raw (FDC 2709576): 437.1 ug, 1 cup 36 g = 157.4 ug; Cabbage, green, raw (FDC 2709773): 59.4 ug, 1 cup 90 g = 53.5 ug
   USDA FNDDS 2021-2023, FDC 2709582, 2709576, 2709773 · checked 2026-10-01
4. cbcl-r4-08 · clinical trial, non-randomized
   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 2026-10-01
5. cbcl-r4-09 · RCT
   Twenty-five subjects were fed 50 g of either raw "Jade Cross" Brussels sprouts (high glucobrassicin concentration) or "Blue Dynasty" cabbage (low glucobrassicin concentration) once daily for 3 days... Urinary DIM was consistently and significantly higher after Brussels sprouts feeding than after cabbage feeding, as evidenced by an average difference of 8.73 pmol/mg creatinine (95% confidence interval, 5.36-12.10; P = 0.00002).
   Cancer Epidemiol Biomarkers Prev, 2014 · checked 2026-10-01
6. cbcl-r4-10 · RCT
   Urinary DIM excretion increased predictably with increasing glucobrassicin dose and plateaued between 200 and 300 μmol of glucobrassicin. The association between glucobrassicin dose and urinary DIM was strong and positive (R2 = 0.68).
   Cancer Prev Res (Phila), 2016 · checked 2026-10-01
7. cbcl-r4-04 · USDA Table of Nutrient Retention Factors, dataset
   USDA-RETN-R6:3005 VEG,GREENS,BOILED,WATER COVER DRAIN, group Vegetables and Vegetable Products: vitamin_c_mg 55% retained, folate_total_ug 60%, thiamin_mg 80%, potassium_mg 85%, calcium_mg 95%
   USDA Table of Nutrient Retention Factors, Release 6, 2007, Retn_Code 3005 · checked 2026-10-01
8. cbcl-r4-05 · CoFID 2021, dataset
   CoFID 13-510 Cabbage, green, raw: Vitamin C 48 mg, Calcium 56 mg per 100 g; CoFID 13-511 Cabbage, green, boiled in unsalted water: Vitamin C 45 mg, Calcium 54 mg
   CoFID 2021, Public Health England, codes 13-510 and 13-511 · checked 2026-10-01
9. cbcl-r4-12 · meta-analysis of observational studies
   When all studies were pooled, we yielded a significantly inverse association between CV (relative risk = 0.81; 95% confidence interval, 0.75-0.88) intake and gastric cancer risk, with little heterogeneity (Q = 27.27, P = 0.292, I(2) = 12.0%). Specific analysis for cabbage intake yielded similar result.
   Cancer Sci, 2013 · checked 2026-10-01
10. cbcl-r4-13 · allergy case study
    Five of them referred anaphylactic reactions when eating cabbage, and in another 5 patients, cabbage allergy was further confirmed by double-blind placebo-controlled food challenge.
    J Allergy Clin Immunol, 2006 · checked 2026-10-01
11. cbcl-r4-06 · fact sheet
    In addition to spinach, foods with high levels of oxalic acid include collard greens, sweet potatoes, rhubarb, and beans [1]. The bioavailability of calcium from other plants that do not contain these compounds—including broccoli, kale, and cabbage—is similar to that of milk, although the amount of calcium per serving is much lower [3].
    NIH Office of Dietary Supplements, Calcium Fact Sheet for Health Professionals · checked 2026-10-01
12. cbcl-r4-14 · 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 2026-10-01
13. cbcl-r4-07 · fact sheet
    People taking warfarin and similar anticoagulants need to maintain a consistent intake of vitamin K from food and supplements because sudden changes in vitamin K intakes can increase or decrease the anticoagulant effect [45].
    NIH Office of Dietary Supplements, Vitamin K Fact Sheet for Health Professionals · checked 2026-10-01
14. cbcl-r4-11 · 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 2026-10-01