Asparagus and broccoli: vitamin C on one side, folate on the other

In a crossover trial in 12 healthy adults, stirring 1 g of mustard powder into 7.1 oz (200 g) of cooked broccoli raised sulforaphane in 24-hour urine from 9.8 to 44.7 µmol per gram of creatinine, a marker of exposure with no health outcome measured. Per 100 g raw, USDA lab samples give broccoli about ten times the vitamin C of green asparagus, 91.3 mg against 9.2 mg, before any cooking losses. Asparagus wins on folate, 182.5 mcg against 65.0 mcg, and broccoli folate ranged from 15 to 182 mcg between samples. The broccoli trials used the vegetable itself. The only asparagus trial we found gave 20 trained young men 30 mg a day of 20-hydroxyecdysone extracted from asparagus for 12 weeks, a dose far above what food provides, so it says nothing about eating asparagus.

How much is actually in it

• Per 100 g raw, USDA lab samples give broccoli about ten times the vitamin C of green asparagus (91.3 vs 9.2 mg). — USDA Foundation Foods, raw, 5 broccoli and 8 asparagus samples Evidence E source
  Vitamin C 91.3 mg (range 56.7 to 105) vs 9.15 mg (5.38 to 12.4)
• Per 100 g raw, green asparagus carries more folate than broccoli (182.5 vs 65.0 ug), while broccoli folate swings from 15 to 182 ug between samples. — USDA Foundation Foods, raw, 8 samples each Evidence E source
  Folate 182.5 vs 65.0 ug; broccoli spread 257%; fiber 1.9 vs 2.4 g

What a real portion looks like

• In the US dietary survey, a cup of raw broccoli weighs 3.2 oz (90 g) while a cup of raw asparagus weighs 4.8 oz (135 g), and one asparagus spear is about 16 g. — US FNDDS portion weights Evidence E source
  Cup 90 g vs 135 g; unspecified portion 1.6 oz (45 g) vs 68 g

What your body absorbs

• In a crossover RCT in 12 adults, adding 1 g mustard powder to 200 g cooked broccoli raised sulforaphane uptake more than fourfold. — Healthy adults, single meals, 24-hour urine (n = 12) Evidence B source
  Urinary SF-NAC 9.8 vs 44.7 umol/g creatinine
• In a crossover RCT in 10 adults eating broccoli soup, only 2 to 15% of the glucoraphanin eaten came out as sulforaphane in urine, varying by person. — Healthy adults, 300 g broccoli soup per phase (n = 10) Evidence B source
  Sulforaphane excreted 2 to 15% of glucoraphanin dose

What cooking and storage change

• By the USDA retention table for green vegetables, boiling in water to cover and draining keeps about 55% of vitamin C, versus 70% when the cooking water is used. — USDA group Vegetables and Vegetable Products, greens Evidence E source
  Vitamin C retained 55% (boiled, drained) vs 70% (water used)

What it does to your health

• In an 18-day controlled feeding crossover RCT in 18 adults, 7.1 oz (200 g) of cooked broccoli a day cut gut Firmicutes by 9% and raised Bacteroidetes by 10%. — Healthy adults fed at weight maintenance, two 18-day periods (n = 18) Evidence B source
  Firmicutes -9% (P=.05), Bacteroidetes +10% (P=.03), Bacteroides +8% (P=.02)
• Observational data link higher broccoli intake with an 11% lower cancer risk in cohort studies. — 12 cohorts (699,482 people) and 23 case-control studies (n = 699482) Evidence C source
  Cohorts RR 0.89 (95% CI 0.82 to 0.96); case-control OR 0.64 (0.58 to 0.70)

Safety, limits and interactions

• Raw broccoli holds about 102 ug vitamin K per 3.5 oz (100 g) in USDA samples, while USDA lab samples give no vitamin K value for green asparagus. — USDA Foundation Foods, raw broccoli, 8 samples Evidence E source
  Phylloquinone 102 ug (range 76.6 to 136); asparagus not measured in Foundation

Who this works differently for

• In a 2-week crossover RCT in 18 older adults with raised blood pressure, 300 g a day of cruciferous vegetable soup lowered glucose variability by 2 percentage points versus root vegetables. — Non-diabetic adults with elevated blood pressure, median age 68, 89% women (n = 18) Evidence B source
  Glycemic variability MD -2.0% (95% CI -2.8 to -1.1); 2-h postprandial glucose -2.5 mg/dL (-0.14 mmol/L)

What is still unknown

• In a 12-week double-blind RCT, 20 resistance-trained men took 30 mg a day of asparagus-derived 20-hydroxyecdysone or a placebo, an extract dose, not the vegetable. — Resistance-trained young men, 12 weeks (n = 20) Evidence B source
  Greater arm fat reduction vs placebo (p<0.05); magnitude not in abstract

The bottom line

Much of the broccoli compound never arrives. In 10 adults eating 11 oz (300 g) of broccoli soup, only 2 to 15% of the glucoraphanin eaten came out as sulforaphane in urine, varying by person, in a soup in which the plant enzyme myrosinase was denatured. Cooking water carries vitamin C away. USDA retention factors for green vegetables keep about 55% of vitamin C when they are boiled in water to cover and drained, against 70% when the cooking water is used, a group value that was not measured on broccoli or asparagus specifically. A cup of raw broccoli weighs 3.2 oz (90 g) and a cup of raw asparagus 135 g in US survey data, and one spear is about 16 g. In an 18-day controlled feeding trial in 18 adults, 7.1 oz (200 g) of cooked broccoli a day cut gut Firmicutes by 9% and raised Bacteroidetes by 10%, a bacterial change from a diet that also included 20 g of raw daikon radish. In 18 adults with a median age of 68 and raised blood pressure, 300 g a day of cruciferous vegetable soup for 2 weeks lowered glucose variability by 2.0 percentage points (95% CI 1.1 to 2.8) against root vegetables, a secondary outcome from a vegetable mix. Observational data from 12 cohorts link higher broccoli intake with an 11% lower cancer risk (RR 0.89, 95% CI 0.82 to 0.96), an association that does not show cause. The safety section holds one fact, and it touches medicines. Raw broccoli holds about 102 mcg of vitamin K per 3.5 oz (100 g) in USDA samples, a figure the card flags as relevant to people taking warfarin, and USDA has no sampled vitamin K value for green asparagus. We have no card on pregnancy, children or allergy for either vegetable.

Sources

1. asb-r5-01 · food composition dataset
   Broccoli, raw: Vitamin C, total ascorbic acid 91.3 mg (range 56.7-105.0, median 99.3, 5 samples, spread 53%). Asparagus, green, raw: Vitamin C, total ascorbic acid 9.153 mg (range 5.38-12.4, median 9.52, 8 samples, spread 77%)
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-10-02
2. asb-r5-02 · food composition dataset
   Asparagus, green, raw: Folate, total 182.5 ug (range 143.0-206.6, 8 samples); Fiber, total dietary 1.883 g. Broccoli, raw: Folate, total 65.0 ug (range 15.0-182.0, median 45.0, 8 samples, spread 257%); Fiber, total dietary 2.4 g
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-10-02
3. asb-r5-04 · portion dataset
   Broccoli, raw (fdc_id 2709643): 1 cup 90 g; 1 floweret 10 g; Quantity not specified 45 g. Asparagus, raw (fdc_id 2709767): 1 spear 16 g; 1 cup 135 g; Quantity not specified 68 g
   USDA FNDDS, Broccoli raw (72201100) and Asparagus raw (75100800) · checked 2026-10-02
4. asb-r5-06 · RCT
   When study subjects ingested cooked broccoli alone, mean urinary SF-NAC excreted was 9.8 ± 5.1 μmol per g creatinine, and when cooked broccoli was consumed with mustard powder, this increased significantly to 44.7 ± 33.9 μmol SF-NAC per gram creatinine.
   Mol Nutr Food Res, 2018 · checked 2026-10-02
5. asb-r5-07 · RCT
   The percentage of sulforaphane excreted in 24 h relative to the amount of glucoraphanin consumed varies among volunteers from 2 to 15%, but does not depend on the broccoli genotype.
   Mol Nutr Food Res, 2018 · checked 2026-10-02
6. asb-r5-05 · retention table
   3005 VEG,GREENS,BOILED,WATER COVER DRAIN: vitamin C 55% retained; 3006 VEG,GREENS,BOILED,WATER USED: vitamin C 70% retained
   USDA Table of Nutrient Retention Factors, Release 6 (2007), codes 3005 and 3006 · checked 2026-10-02
7. asb-r5-09 · RCT
   Broccoli consumption decreased the relative abundance of Firmicutes by 9% compared to control (P=.05), increased the relative abundance of Bacteroidetes by 10% compared to control (P=.03) and increased Bacteroides by 8% relative to control (P=.02).
   J Nutr Biochem, 2019 · checked 2026-10-02
8. asb-r5-10 · meta-analysis of observational studies
   The results suggest an inverse association between broccoli consumption and the risk of cancer both in case-control studies (OR: 0.64, 95% CI from 0.58 to 0.70, p < 0.001; Q = 35.97, p = 0.072, I2 = 30.49%-moderate heterogeneity; τ2 = 0.016) and cohort studies (RR: 0.89, 95% CI from 0.82 to 0.96, p = 0.003
   Nutrients, 2024 · checked 2026-10-02
9. asb-r5-03 · food composition dataset
   Broccoli, raw: Vitamin K (phylloquinone) 102.0 ug (range 76.6-136.0, median 98.7, 8 samples, spread 58%). Asparagus: no Foundation vitamin K row
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-10-02
10. asb-r5-08 · RCT
    Glycaemic variability was lower in the active versus control (mean difference: -2.0%, 95% CI -2.8, -1.1, p < 0.001).
    Diabetes Obes Metab, 2025 · checked 2026-10-02
11. asb-r5-11 · RCT
    Twenty healthy males were randomly assigned in a double-blind design to receive either a placebo (PLA; n=10) or 30 mg/d of 20E (n=10) for 12 wk, during which all participants performed supervised RT three times per week.
    J Nutr Sci Vitaminol (Tokyo), 2025 · checked 2026-10-02