Asparagus vs Brussels sprouts: folate on one side, vitamin C on the other

In a 3-week feeding trial in 10 healthy non-smoking men, 11 oz (300 g) of cooked Brussels sprouts a day lowered a urine marker of oxidative DNA damage by 28 percent, while the control group saw no change. That is a biomarker from 1995, in ten people, at about two cups a day, and it is the strongest human result on this page. Asparagus has no trial of the vegetable itself on any health outcome that we could find. The clearest difference between the two is on the label. Per 100 g raw, Brussels sprouts average 143 mg of vitamin C (85 to 197 mg across 8 USDA samples) against 9 mg in green asparagus. Asparagus averages 183 ug of folate, about twice the 86 ug in the sprouts.

How much is actually in it

• Raw Brussels sprouts average 143 mg vitamin C, 4.8 g fiber and 477 mg potassium per 3.5 oz (100 g), with vitamin C ranging from 85 to 197 mg across 8 samples. — USDA Foundation samples of raw Brussels sprouts (n = 8) Evidence E source
  Per 100 g: vitamin C 142.9 mg (84.6-197.0); fiber 4.785 g (4.15-5.27); potassium 476.8 mg (447-513); folate 86 ug (48-140); protein 4.0 g
• Raw green asparagus averages 183 ug folate, 9 mg vitamin C, 1.9 g fiber and 278 mg potassium per 3.5 oz (100 g), so it carries twice the folate of Brussels sprouts but far less vitamin C. — USDA Foundation samples of raw green asparagus (n = 8) Evidence E source
  Per 100 g: folate 182.5 ug (143.0-206.6); vitamin C 9.15 mg (5.38-12.4); fiber 1.883 g (1.59-2.21); potassium 277.5 mg (254-301)

What a real portion looks like

• US survey data weigh a cup of cooked asparagus at 180 g (one spear 16 g) and a cup of cooked Brussels sprouts at 155 g (one sprout 20 g). — FNDDS portion weights, fresh, cooked, no added fat (n = -) Evidence E source
  Asparagus 1 cup 180 g, 1 spear 16 g, default 90 g; Brussels sprouts 1 cup 155 g, 1 sprout 20 g, default 78 g

What cooking and storage change

• USDA factors for vegetables boiled in covering water and drained keep 65% of folate and 75% of vitamin C, while most minerals stay at 90-95%. — USDA group factor for vegetables and vegetable products, boiled, water cover, drained (n = -) Evidence E source
  Folate 65%; vitamin C 75%; thiamin 80%; potassium 90%; iron, magnesium, zinc 95%

What it does to your health

• In a 3-week trial in 10 healthy men, eating 11 oz (300 g) of cooked Brussels sprouts a day lowered a urinary marker of oxidative DNA damage by 28%. — 10 healthy non-smoking men, 300 g/day cooked Brussels sprouts vs glucosinolate-free vegetable, 3 weeks (n = 10) Evidence B source
  Urinary 8-oxodG -28% (P = 0.039) in sprouts group, no change in controls
• In a crossover trial in 10 adults, a week of 11 oz (300 g) cooked Brussels sprouts a day raised rectal levels of the enzymes GST-alpha and GST-pi by 30% and 15%. — 10 healthy non-smokers, 300 g/day cooked Brussels sprouts for 7 days, crossover (n = 10) Evidence B source
  Rectal GST-alpha +30%, GST-pi +15%; glutathione unchanged
• In a meta-analysis of prospective studies, Brussels sprouts were among the vegetables linked with higher, not lower, hypertension risk, based on 2 to 5 studies. — 18 prospective studies, 451,291 participants (n = 18 studies) Evidence C source
  Positive association for Brussels sprouts and cruciferous vegetables (n = 2-5 studies); vegetables overall RR 1.00 per 200 g/day
• Observational data from 177,148 UK Biobank adults link a high liking for asparagus with 31% lower all-cause mortality over 3.4 years. — 177,148 UK Biobank participants, food preference questionnaire, mean follow-up 3.4 years (n = 177148) Evidence C source
  Asparagus preference HR 0.69 (95% CI 0.62-0.77)

Safety, limits and interactions

• In a 3-week trial in 10 men, 11 oz (300 g) of cooked Brussels sprouts a day cut the activity of the liver enzyme FMO3, raising the urinary trimethylamine ratio 2.6 to 3.2-fold. — 10 healthy non-smoking men, 300 g/day cooked Brussels sprouts vs glucosinolate-free diet, 3 weeks (n = 10) Evidence B source
  Urinary trimethylamine to TMAO ratio x2.6-3.2 (lower FMO3 activity)
• Pooled diet trials found that eating cruciferous vegetables such as Brussels sprouts raises the activity of the drug-metabolizing enzyme CYP1A2 by 20-40%. — 23 dietary intervention trials in humans, broccoli, Brussels sprouts, cabbage, cauliflower, radish, watercress (n = 23 trials) Evidence C source
  CYP1A2 +20-40%; GST-alpha +15-35%
• In northwest Mexico, Cryptosporidium was found on 29% of fresh asparagus bundles, more often in open-air market and sub-standard lots than in export lots. — 150 asparagus bundles from export, sub-standard and open-air market sources, Sonora, Mexico (n = 150) Evidence C source
  Cryptosporidium 29%, Giardia 5%, Cyclospora 3%

What people believe that the data does not support

• In a UK survey of 516 adults, 23% believed Brussels sprouts cause flatulence, though flatulence was rarely the symptom that worried people. — 516 UK adults, online questionnaire, 85% female, median age 38 (n = 516) Evidence C source
  23% attribute flatulence to Brussels sprouts; beans 34%
• The EU did not authorize the claim that asparagus supports kidney excretion or urinary flow, and no claim names Brussels sprouts. — EU health claim applications (n = -) Evidence E source
  Status Non-authorized

Who this works differently for

• In a crossover trial in 5 men and 5 women, a week of 11 oz (300 g) Brussels sprouts a day raised plasma GST-alpha 1.5-fold in men but not in women. — 5 men and 5 women, non-smokers, 300 g/day cooked Brussels sprouts for 1 week (n = 10) Evidence B source
  Plasma GST class-alpha x1.5 in men (P = 0.031), no change in women (P = 0.317)

The bottom line

Brussels sprouts also carry more fiber, 4.8 g per 3.5 oz (100 g) against 1.9 g, and more potassium, 477 mg against 278 mg, both raw. A cup of cooked sprouts weighs 5.5 oz (155 g) and a cup of cooked asparagus 180 g, with one spear at 16 g. Boiling in water that is then drained costs some of what makes each one distinctive. USDA group factors for boiled vegetables keep 75 percent of vitamin C and 65 percent of folate, while potassium stays at 90 percent. Those factors date from 1975 and were never measured on these two vegetables. The other sprout trials are equally small and short. In a randomized crossover in 10 adults, a week of 11 oz (300 g) a day raised the enzymes GST-alpha and GST-pi in the rectal lining by 30 and 15 percent. In another, with 5 men and 5 women, plasma GST-alpha rose 1.5-fold in the men and did not change significantly in the women. Any link from these enzymes to cancer is the authors' hypothesis. The observational data are weak for both. In pooled prospective studies, Brussels sprouts were among the vegetables with a positive association with hypertension, based on only 2 to 5 studies, and vegetables overall showed no link (RR 1.00 per 200 g a day). In 177,148 UK Biobank adults, a strong liking for asparagus went with 31 percent lower all-cause mortality over 3.4 years (HR 0.69, 95% CI 0.62 to 0.77). That measures taste preference, and people who like asparagus may differ in many other ways. The EU turned down a claim that asparagus supports kidney excretion or urinary flow. In a UK online survey of 516 adults, 23 percent blamed Brussels sprouts for flatulence, a perception, since nobody measured gas. The cautions fall mostly on the sprouts. At 300 g a day for 3 weeks, Brussels sprouts cut the activity of the liver enzyme FMO3 in 10 men, raising the urine trimethylamine ratio 2.6 to 3.2-fold. Pooled diet trials of cruciferous vegetables found CYP1A2, an enzyme that clears some medicines, rose by 20 to 40 percent, though the trials varied in design and the authors call the clinical meaning unclear. If you take a drug with a narrow dose range, a sudden big change in how many sprouts you eat is worth mentioning to your prescriber. For asparagus, a survey of 150 market bundles in Sonora, Mexico found Cryptosporidium on 29 percent, more often in open-air market and sub-standard lots than in export lots. We have no card on pregnancy or children for either vegetable.

Sources

1. absp-r2-01 · dataset
   Brussels sprouts, raw: Vitamin C, total ascorbic acid 142.9 MG range 84.6-197.0 samples 8; Fiber, total dietary 4.785 G range 4.15-5.27 samples 8; Potassium, K 476.8 MG range 447.0-513.0 samples 8; Folate, total 86.0 UG range 48.0-140.0 samples 8
   USDA FoodData Central, Foundation Foods (release 2026-04-30), Brussels sprouts, raw · checked 2026-09-30
2. absp-r2-02 · dataset
   Asparagus, green, raw: Folate, total 182.5 UG range 143.0-206.6 samples 8; Vitamin C, total ascorbic acid 9.153 MG range 5.38-12.4 samples 8; Fiber, total dietary 1.883 G range 1.59-2.21 samples 8; Potassium, K 277.5 MG range 254.0-301.0 samples 8
   USDA FoodData Central, Foundation Foods (release 2026-04-30), Asparagus, green, raw · checked 2026-09-30
3. absp-r2-03 · dataset
   FNDDS 75202011 Asparagus, fresh, cooked, no added fat (fdc_id 2709834): 1 spear 16 g; 1 cup 180 g; Quantity not specified 90 g. FNDDS 75209011 Brussels sprouts, fresh, cooked, no added fat (fdc_id 2709881): 1 cup 155 g; 1 sprout 20 g; Quantity not specified 78 g
   USDA FNDDS 2021-2023, food codes 75202011 and 75209011 (fdc_id 2709834, 2709881) · checked 2026-09-30
4. absp-r2-04 · dataset
   USDA-RETN-R6:3775 VEG,OTHER,BLD,WATER COVER,DRAINED: folate_total_ug 65%; vitamin_c_mg 75%; thiamin_mg 80%; potassium_mg 90%; iron_mg 95%; zinc_mg 95%
   USDA Table of Nutrient Retention Factors, Release 6 (2007), code 3775 Veg, other, boiled, water cover, drained · checked 2026-09-30
5. absp-r2-05 · RCT
   The effect of consumption of Brussels sprouts on levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in human urine was investigated in 10 healthy, male, non-smoking volunteers. ... In contrast, in the sprouts group the levels of 8-oxodG were decreased by 28% during the intervention period (P = 0.039).
   Carcinogenesis, 1995 · checked 2026-09-30
6. absp-r2-06 · RCT (crossover)
   Ten healthy non-smoking volunteers were randomly assigned to two groups in a cross-over design. Five persons started on a glucosinolate-free diet (control period), while the other five consumed 300 g/day cooked Brussels sprouts, at the expense of 300 g glucosinolate-free vegetables (sprouts period). ... As a result of the dietary regimen rectal GST-alpha and -pi levels were slightly increased at the end of the sprouts period, by 30 and 15% respectively.
   Carcinogenesis, 1995 · checked 2026-09-30
7. absp-r2-10 · cohort meta-analysis
   Inverse associations were observed for apples or pears, blueberries, raisins or grapes, avocado, broccoli, carrots and lettuce, while positive associations were observed for cantaloupe, Brussels sprouts, cruciferous vegetables, and total and fried potatoes (n = 2-5).
   Eur J Nutr, 2023 · checked 2026-09-30
8. absp-r2-11 · cohort
   We included 177,148 UK Biobank participants who completed a food preference questionnaire (FPQ), with a mean follow-up of 3.4 years (607,779 person-years; 3355 deaths). ... Higher preference for asparagus (hazard ratio (95% confidence interval)): 0.69 (0.62, 0.77))
   Sci Rep, 2026 · checked 2026-09-30
9. absp-r2-08 · RCT
   The effect of consumption of glucosinolate-containing Brussels sprouts on flavin-containing monooxygenase functional activity in humans was investigated in 10 healthy, male, non-smoking volunteers. ... In the control group similar trimethylamine to trimethylamine N-oxide ratios were observed, while in the sprouts group the trimethylamine to trimethylamine N-oxide ratios were increased 2.6- to 3.2-fold, and thus flavin-containing monooxygenase functional activity was decreased significantly.
   Biochem Pharmacol, 1999 · checked 2026-09-30
10. absp-r2-09 · meta-analysis
    Twenty-three dietary intervention trials with drug metabolism end points were identified across Embase, Medline, and the Cochrane Controlled Register of Trials (CENTRAL). ... 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 2026-09-30
11. absp-r2-14 · survey
    The pathogens Cryptosporidium spp. (29%) G. intestinalis (5%) and Cyclospora spp. (3%) were found in the asparagus sold in the region. The prevalence of Cryptosporidium spp. was higher in both the sub-standard asparagus and the product sampled from the open-air markets than in the samples for exportation (P < 0.05).
    Trop Biomed, 2019 · checked 2026-09-30
12. absp-r2-12 · survey
    Of 516 respondents (85% female, median age 38 years), 72.1% reported no existing GI conditions, yet 86% experienced GI symptoms in the past month ... The most common perceptions were that beans (34%) and Brussels sprouts (23%) cause flatulence
    Eur J Nutr, 2025 · checked 2026-09-30
13. absp-r2-13 · regulatory decision
    POL-HC-6652 Asparagus officinalis Supports the excretory function of the kidneys /contributes to urinary flow Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-6652, snapshot 2026-09-21 · checked 2026-09-30
14. absp-r2-07 · RCT (crossover)
    Five male and five female non-smoking volunteers were randomly assigned to two groups in a crossover design. ... At the end of the sprouts period, a significant increase (1.5-fold) in plasma class-alpha GST levels was observed in males but not in females (control versus sprouts, paired t-test; P-values 0.031 and 0.317 respectively)
    Carcinogenesis, 1995 · checked 2026-09-30