Cabbage and kale: one family, very different numbers

The strongest trial here used kale in a form you will not find in the produce aisle. Thirty adults with type 2 diabetes ate either three bars a day of freeze-dried kale, equal to about 12 oz (341 g) of fresh kale, or placebo bars for 12 weeks. HbA1c fell by 1.37 on kale and rose by 1.36 on placebo, in units the paper does not state, and 13 people dropped out. It is one small trial at a very high dose, and nobody has repeated it. We found no trial of cabbage with a clinical outcome at all. On the plate, kale is the denser leaf. Raw kale carries about 390 ug vitamin K, 93 mg vitamin C and 254 mg calcium per 3.5 oz (100 g) in USDA sampling of 3 to 5 samples. Raw green cabbage has about 59 ug, 40 mg and 42 mg. UK tables list kale calcium at 130 mg per 3.5 oz (100 g), about half the US figure, and neither table explains the gap. A cup of raw kale weighs 0.88 oz (25 g) and a cup of shredded cabbage 90 g, so a cup of each is a very different amount of leaf.

How much is actually in it

• Raw kale carries about 390 ug vitamin K, 93 mg vitamin C and 254 mg calcium per 3.5 oz (100 g) in USDA sampling, against about 59 ug, 40 mg and 42 mg for raw green cabbage. — USDA Foundation Foods analytical samples: Kale, raw (3-5 samples) and Cabbage, green, raw (8 samples) (n = 3-8 samples per nutrient) Evidence E source
  Kale vitamin K 369-422 ug, vitamin C 84.4-104 mg, calcium 203-281 mg; green cabbage vitamin K 41.6-82.9 ug, vitamin C 34.8-56.3 mg, calcium 23.1-64.1 mg per 3.5 oz (100 g)
• UK tables give raw curly kale 130 mg calcium and 110 mg vitamin C per 3.5 oz (100 g) and average raw cabbage 56 mg and 48 mg, so the UK calcium figure for kale is about half the US one. — CoFID 2021 entries Curly kale, raw (13-234) and Cabbage, average, raw (13-582) (n = 2 entries) Evidence E source
  Kale calcium 130 vs 254 mg per 3.5 oz (100 g) in USDA Foundation; vitamin C 110 vs 93.4 mg

What a real portion looks like

• A cup of raw kale weighs 0.88 oz (25 g) in the US survey database and a cup of raw green cabbage 90 g, so a cup of shredded cabbage is more than three times heavier. — USDA FNDDS household measures for Kale, raw (72119190) and Cabbage, green, raw (75103000) (n = 5 measures for kale, 4 for cabbage) Evidence E source
  Kale 1 cup 25 g, 1 leaf 10 g, salad guideline amount 50 g; cabbage 1 cup 90 g, 1 leaf 25 g, 1 head 900 g

What your body absorbs

• In 7 healthy adults eating 14 oz (400 g) kale with 30 g oil, only about 4.7% of the labeled kale vitamin K reached the blood. — Seven healthy volunteers, single 14 oz (400 g) serving of kale with 30 g vegetable oil (n = 7) Evidence C source
  Mean bioavailability 4.7% (n 6), peak 2.1 nmol/l at 6-10 h
• In 16 young women, iron absorption from bread with 150 g kale was 10.7% and adding 1.26 g oxalic acid did not change it (11.5%). — Sixteen apparently healthy women (18-45 years, <132 lb (60 kg) body weight) (n = 16) Evidence B source
  10.7% vs 11.5% iron absorption, P=0.86

What cooking and storage change

• In 22 healthy adults eating Ethiopian kale for 5 days, cooked leaves cut lab-induced DNA damage in blood cells by about 33-35%, while raw leaves reached 21% without significance. — Twenty-two healthy subjects, five days per preparation (n = 22) Evidence B source
  Cooked: -35% (+S9) and -33% (-S9), p<=0.01; raw: -21% (+S9), p=0.08
• In the same 22 volunteers, 5 days of cooked Brassica leaves raised telomerase activity in CD8+ cells by 25%, and raw leaves did not. — 22 healthy volunteers, five-day intervention (n = 22) Evidence B source
  +25% telomerase activity in CD8+ cells after cooked material, p < 0.05

What it does to your health

• In 30 adults with type 2 diabetes, three kale bars a day (about 341 g fresh kale) for 12 weeks lowered HbA1c, insulin resistance and body weight compared with placebo bars. — Thirty T2D patients, 12 weeks (n = 30) Evidence B source
  Significant reduction in HbA1c, insulin resistance, body weight and calorie intake vs control
• In that trial HbA1c fell by 1.37 units on kale bars and rose by 1.36 on placebo over 12 weeks, and HOMA-IR fell by 0.95 against a 0.15 rise. — Thirty T2D patients randomized, 12 weeks (n = 30) Evidence B source
  HbA1c -1.368 +/- 0.8591 vs +1.364 +/- 0.7894 (p = 0.04); HOMA-IR -0.95 +/- 0.34 vs 0.15 +/- 0.28 (p < 0.03)
• Observational data link high intake of broccoli and cabbage with lower gastric cancer risk (RR 0.64, 95% CI 0.47-0.87) in a meta-analysis of 89 studies. — 81 articles covering 89 observational studies (n = 89 studies) Evidence C source
  RR 0.64 (95% CI 0.47-0.87) gastric cancer; all GI cancers RR 0.81 (0.76-0.87) for cruciferous vegetables
• An umbrella review of 137 associations rated cabbage among only 8 protective factors for gastric cancer with strong epidemiologic evidence. — 76 meta-analyses of observational studies, 137 associations (n = 76 meta-analyses) Evidence C source
  Cabbage graded strong evidence, protective; size not in abstract

Safety, limits and interactions

• According to the NIH Office of Dietary Supplements, people on warfarin need a steady vitamin K intake from food, because sudden changes can raise or lower the drug's effect. — people taking warfarin and similar anticoagulants Evidence E source
  Direction only
• In 17 patients with cabbage allergy, 5 reported anaphylaxis, and the lipid transfer protein Bra o 3 was a major allergen cross-reacting with mugwort pollen and peach. — 17 patients allergic to cabbage (n = 17) Evidence D source
  5 of 17 anaphylactic reactions; Bra o 3 skin prick positive in 12 of 14 (86%)
• A meta-analysis of 35 vegetable species found kale among the strongest thallium accumulators from soil, with a bioconcentration factor of 0.133. — 35 vegetable species from published soil and crop data (n = 35 species) Evidence C source
  Tl bioconcentration factor kale 0.133, taro 0.060; soil Tl threshold for kale 0.24-4.89 mg/kg
• A California household of a mother and three young children had raised urine thallium traced to commercial kale chips measured at about 2 mg/kg thallium. — a mother and her three young children, one household (n = 4) Evidence D source
  Child urine Tl peak 10.5 ug/g creatinine vs reference <=0.8; kale chips 1.98 and 2.15 mg/kg
• Pooled Ethiopian market surveys found cabbage among the raw vegetables most often carrying parasites (52.9%) and bacteria (20.0%). — Twenty-nine studies with 6659 vegetables and fruits, Ethiopia (n = 6659 samples) Evidence C source
  Cabbage parasites 52.9%, bacteria 20.0%; overall contamination 48.76% (95% CI 40.78-56.74)

What people believe that the data does not support

• A systematic review of 123 in vitro, animal and human studies found 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 (n = 123 articles) Evidence C source
  No adverse thyroid effect with adequate iodine; size not pooled
• The EU rejected a claim that cabbage-family vegetables are particularly rich in compounds that protect cells and DNA from oxidative damage. — — Evidence E source
  Status non-authorized

Who this works differently for

• Among 225 Japanese adults with chronic kidney disease, the highest intake of vegetables such as cabbage, radish and onion went with lower odds of metabolic acidosis (OR 0.28). — 225 eligible patients (median age 72 years, 33.8% women) with non-dialysis CKD (n = 225) Evidence C source
  Adjusted OR 0.28 (95% CI 0.10-0.79), highest vs lowest intake

The bottom line

How much you absorb is lower than the table suggests. In 7 healthy adults eating a single 14 oz (400 g) serving of kale with 30 g oil, only about 4.7% of the kale vitamin K reached the blood. In 16 young women, iron absorption from bread rolls with 150 g kale was 10.7%, and adding 1.26 g oxalic acid left it at 11.5%, a difference that did not reach significance. Cooking did not ruin the leaf in the one trial that compared it. In 22 healthy adults eating Ethiopian kale, a different species from supermarket kale, for 5 days, cooked leaves cut lab-induced DNA damage in blood cells by 33 to 35%. Raw leaves reached 21%, which did not reach significance. Cooked leaves also raised telomerase activity in one type of immune cell by 25%. Both are blood markers measured in the lab, not disease outcomes. Observational data link high intake of broccoli and cabbage with lower gastric cancer risk, RR 0.64 (95% CI 0.47 to 0.87) across 89 studies. An umbrella review rated cabbage among 8 protective factors for gastric cancer with strong epidemiologic evidence and gave no size. Both describe association, and diets rich in cabbage differ in many other ways. The old worry about the thyroid is not supported when iodine intake is adequate. A review of 123 in vitro, animal and human studies found no adverse thyroid effect from brassicas in the daily diet when iodine intake is adequate. The EU rejected a claim that these vegetables are particularly rich in compounds protecting cells and DNA. Who should be careful. If you take warfarin, the NIH Office of Dietary Supplements says to keep vitamin K intake from food steady, because sudden changes can raise or lower the drug's effect, and kale carries several times more than cabbage. In a case series of 17 people allergic to cabbage, 5 reported anaphylaxis, and the allergen Bra o 3 cross-reacted with mugwort pollen and peach. Kale was among the strongest soil thallium accumulators of 35 species, with a bioconcentration factor of 0.133, in data drawn mostly from contaminated soils. One California mother and her three young children had raised urine thallium traced to commercial kale chips measured at about 2 mg/kg, a single household. In Ethiopian market surveys, 52.9% of raw cabbage carried parasites and 20.0% bacteria, figures that may not carry over to other countries. We found no data on pregnancy. Among 225 Japanese adults with chronic kidney disease, the highest intake of vegetables such as cabbage, radish and onion went with lower odds of metabolic acidosis, OR 0.28 (95% CI 0.10 to 0.79), for that vegetable group as a whole.

Sources

1. cbkl-daily-r1-01 · food composition dataset
   Kale, raw: vitamin K (phylloquinone) 390.0 ug (369.0-422.0, 3 samples), vitamin C 93.4 mg (84.4-104.0, 5 samples), calcium 254.0 mg (203.0-281.0, 5 samples) || Cabbage, green, raw: vitamin K (phylloquinone) 59.4 ug (41.6-82.9, 8 samples), vitamin C 40.34 mg (34.8-56.3, 8 samples), calcium 41.84 mg (23.1-64.1, 8 samples) per 100 g
   USDA FoodData Central, Foundation Foods, release 2026-04-30 (Kale, raw; Cabbage, green, raw) · checked 2026-09-28
2. cbkl-daily-r1-02 · food composition dataset
   Curly kale, raw (13-234): Calcium 130 mg, Vitamin C 110 mg || Cabbage, average, raw (13-582): Calcium 56 mg, Vitamin C 48 mg per 100 g
   CoFID 2021, Public Health England / OGL v3.0, codes 13-234 and 13-582 · checked 2026-09-28
3. cbkl-daily-r1-03 · reference dataset
   Kale, raw, FNDDS 72119190: 1 leaf 10 g | 1 baby leaf 1 g | 1 cup 25 g | Guideline amount in salad 50 g | Quantity not specified 13 g || Cabbage, green, raw, FNDDS 75103000: 1 cup 90 g | 1 leaf 25 g | 1 head 900 g | Quantity not specified 45 g
   USDA FNDDS 2021-2023, Kale raw code 72119190 and Cabbage green raw code 75103000 · checked 2026-09-28
4. cbkl-daily-r1-04 · isotope absorption study
   Seven healthy volunteers ingested a single 400 g serving of kale with 30 g vegetable oil. ... Modelling results demonstrated a mean (n 6) bioavailability of phylloquinone from kale to be 4.7%.
   Br J Nutr, 2010 · checked 2026-09-28
5. cbkl-daily-r1-05 · randomized crossover trial
   Sixteen apparently healthy women (18-45 years, <60 kg body weight) ... geometric mean iron absorption from wheat bread rolls with kale (10.7%) did not differ significantly from wheat rolls with kale plus 1.26 g OA added as potassium oxalate (11.5%, P=0.86).
   Eur J Clin Nutr, 2008 · checked 2026-09-28
6. cbkl-daily-r1-06 · randomized crossover trial
   Twenty-two healthy subjects consumed a B. carinata preparation from raw (allyl isothiocyanate-containing) or cooked (no allyl isothiocyanate) leaves for five days in a randomized crossover design. ... 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 2026-09-28
7. cbkl-daily-r1-07 · randomized crossover trial
   the effect of a five-day short-term intervention with raw or cooked leaves of Brassica carinata on telomerase activity in CD4+ and CD8+ T cells from 22 healthy volunteers was investigated in a randomized single-blind, controlled crossover study. ... In CD8+ cells, a significant increase in telomerase activity (25%, p < 0.05) was seen after intervention with the cooked material.
   Nutrients, 2019 · checked 2026-09-28
8. cbkl-daily-r1-08 · randomized controlled trial
   This study was designed as a 12-week, blinded, randomized, controlled trial. Thirty T2D patients were randomly assigned to either a placebo bar (control) or a kale bar (intervention). Participants in the intervention group were instructed to consume three bars/day, each containing 26.25 g of freeze-dried kale (corresponding to approx. 341 g fresh kale/day). ... A significant reduction in HbA1c, insulin resistance, body weight, and calorie intake was observed in the intervention group compared to control.
   Nutrients, 2024 · checked 2026-09-28
9. cbkl-daily-r1-09 · randomized controlled trial
   A decrease of −1.368 ± 0.8591 was noted in the HbA1c of the intervention group from the start to end of this study compared to control, where HbA1c was shown to increase by 1.364 ± 0.7894. The decrease in HbA1c in the group treated with the kale bars was significant compared to control (p = 0.04, Figure 4).
   Nutrients, 2024 · checked 2026-09-28
10. cbkl-daily-r1-10 · meta-analysis of observational studies
    The final analysis included 81 articles covering 89 studies. In comparison to the lowest consumption categories, the highest consumption categories of CV were associated with a lower risk for all GI cancers [rate ratio (RR): 0.81, 95% confidence interval (95% CI) 0.76-0.87]. ... High intake of broccoli and cabbage was associated with a decreased risk of gastric cancer (RR: 0.64; 95% CI: 0.47-0.87) and gallbladder cancer (RR: 0.46; 95% CI: 0.29-0.75).
    Crit Rev Food Sci Nutr, 2024 · checked 2026-09-28
11. cbkl-daily-r1-11 · umbrella review
    A total of 137 associations were examined in 76 articles. ... Only 10 associations had strong epidemiologic evidence, including 2 risk factors (waist circumference and bacon), and 8 protective factors (dietary total antioxidant capacity, vegetable fat, cruciferous vegetable, cabbage, total vitamin, vitamin A, vitamin C, and years of fertility)
    Front Public Health, 2022 · checked 2026-09-28
12. cbkl-daily-r1-12 · 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 Health Professional Fact Sheet · checked 2026-09-28
13. cbkl-daily-r1-13 · case series with food challenges
    A prospective study was performed, recruiting 17 patients allergic to cabbage, and control subjects. ... 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. ... Skin prick test with Bra o 3 showed positive results in 12 of 14 cases (86%).
    J Allergy Clin Immunol, 2006 · checked 2026-09-28
14. cbkl-daily-r1-14 · meta-analysis of environmental data
    Taro and kale had significantly higher capability to accumulate soil Tl among the 35 species studied, with Tl bioconcentration factor values of 0.060 and 0.133, respectively. ... The soil Tl thresholds for kale, lettuce and carrot were in the range of 0.24-4.89, 2.94-3.32 and 3.77-14.43 mg/kg, respectively.
    Sci Total Environ, 2024 · checked 2026-09-28
15. cbkl-daily-r1-15 · case report
    The California Department of Public Health was alerted to a household cluster of elevated urine thallium levels noted among a mother (peak 5.6 µg/g creatinine; adult reference: ≤0.4 µg/g creatinine) and her three young children (peak 10.5 µg/g creatinine; child reference: ≤0.8 µg/g creatinine). ... (ICP-MS analysis measured thallium in kale chips at 1.98 mg/kg and 2.15 mg/kg)
    Int J Environ Res Public Health, 2025 · checked 2026-09-28
16. cbkl-daily-r1-16 · meta-analysis of prevalence studies
    Twenty-nine studies with 6659 vegetables and fruits were included. The overall prevalence of contaminated fresh produce was 48.76% (95% CI: 40.78–56.74). ... Lettuce (61.0%), salad (57.4%), spinach (54.2%), and cabbage (52.9%), were the vegetables most contaminated by parasites, while salad (73.8%), green pepper (35.3%), lettuce (26.0%), and cabbage (20.0%), were the most contaminated by bacteria.
    BMC Infect Dis, 2025 · checked 2026-09-28
17. cbkl-daily-r1-17 · systematic review
    We analyzed the results of 123 articles of in vitro, animal, and human studies ... 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 2026-09-28
18. cbkl-daily-r1-18 · regulatory 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 2026-09-28
19. cbkl-daily-r1-19 · cross-sectional
    Among the 225 eligible patients (median age 72 years, 33.8% women), 43 patients (19.1%) had metabolic acidosis. ... 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)
    BMC Nephrol, 2026 · checked 2026-09-28