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

Pooling 23 dietary trials, diets rich in cruciferous vegetables such as Brussels sprouts raised the activity of CYP1A2, a liver enzyme that clears some drugs, by 20 to 40 percent. The pool mixed randomized and non-randomized trials, and what it means for real drug levels is unclear. Asparagus is not among the vegetables in those trials. The two vegetables split the vitamins between them. Per 100 g raw, green asparagus has about 183 ug of folate and 9 mg of vitamin C, and Brussels sprouts have about 86 ug of folate and 143 mg of vitamin C, from 8 US retail samples each. Brussels sprout folate ranged from 48 to 140 ug across those samples. The word sprouts can also mean raw seed sprouts such as alfalfa or mung bean, and those carry a separate risk. A 2024 Norwegian Salmonella outbreak linked to sprouts made 230 people ill, 33 percent of them needed hospital care, and cases had about 3 times the odds of having eaten sprouts.

How much is actually in it

• Per 100 g raw, green asparagus has about 183 ug folate and 9 mg vitamin C, while Brussels sprouts have about 86 ug folate and 143 mg vitamin C. — USDA Foundation Foods, Asparagus, green, raw and Brussels sprouts, raw, 8 analyzed samples each (n = 16 samples) Evidence E source
  Asparagus: folate 182.5 ug (143-206.6), vitamin C 9.2 mg (5.4-12.4), fiber 1.9 g, potassium 278 mg. Brussels sprouts: folate 86 ug (48-140), vitamin C 142.9 mg (84.6-197), fiber 4.8 g, potassium 477 mg

What a real portion looks like

• In the US food survey one cooked asparagus spear is 16 g and a cup 180 g, while one Brussels sprout is 20 g and a cup 155 g. — USDA FNDDS household measures, Asparagus, fresh, cooked, no added fat (75202011) and Brussels sprouts, fresh, cooked, no added fat (75209011) (n = 2 FNDDS records) Evidence E source
  Asparagus: 1 spear 16 g, 1 cup 180 g, default 90 g. Brussels sprouts: 1 sprout 20 g, 1 cup 155 g, default 78 g

What your body absorbs

• In a trial of healthy adults, sulforaphane from fresh broccoli sprouts was absorbed about 3 times better than the same 200 umol dose from a myrosinase-treated sprout extract. — healthy adults consuming fresh broccoli sprouts or broccoli sprout extract, 200 umol sulforaphane daily, once or split into two doses (n = -) Evidence B source
  About 3 times higher sulforaphane metabolites in plasma and urine after fresh sprouts

What cooking and storage change

• By USDA group factors for vegetables, boiling in water and draining keeps about 75% of vitamin C and 65% of folate, while steaming keeps 85% of folate. — USDA Table of Nutrient Retention Factors Release 6, Vegetables and Vegetable Products group, methods 3775 and 3784 (n = -) Evidence E source
  Boiled, water to cover, drained: vitamin C 75%, folate 65%, thiamin 80%, potassium 90% retained. Steamed: folate 85% retained

What it does to your health

• In a meta-analysis of prospective cohorts, each 100 g a day of Brussels sprouts was associated with 25% higher risk of hypertension, while broccoli was linked to 12% lower risk. — prospective cohort studies of generally healthy adults, subtype analyses (n = 2-5 studies per vegetable) (n = 18 cohorts overall) Evidence C source
  RR per 100 g/day: Brussels sprouts 1.25 (95% CI 1.07-1.47); broccoli 0.88 (0.82-0.94); cruciferous vegetables 1.11 (1.04-1.18)
• In 177,148 UK Biobank adults, a strong liking for asparagus was associated with 31% lower all-cause mortality over 3.4 years, a preference signal rather than measured intake. — 177,148 UK Biobank participants with a food preference questionnaire, mean follow-up 3.4 years, 3355 deaths (n = 177148) Evidence C source
  HR 0.69 (95% CI 0.62-0.77) for high vs low preference for asparagus
• In a 12-week double-blind RCT of 20 healthy men doing supervised resistance training, 30 mg a day of asparagus-derived 20-hydroxyecdysone reduced arm fat more than placebo. — 20 healthy males, supervised resistance training 3 times a week, 12 weeks, 30 mg/d 20-hydroxyecdysone from Asparagus officinalis extract vs placebo (n = 20) Evidence B source
  Arm fat reduction greater than placebo (p < 0.05); arm, leg and abdominal fat reduced within the 20E group

Safety, limits and interactions

• A 2024 Norwegian Salmonella outbreak linked to sprouts made 230 people ill, a third of them hospitalized, and cases had 3 times the odds of having eaten sprouts. — 230 outbreak cases in Norway, October-December 2024, matched case-control study (n = 230) Evidence C source
  33% hospitalized; penalized adjusted OR 3.13 for sprout consumption

What people believe that the data does not support

• In two experiments with 231 adults, a planted false memory of loving asparagus as a child increased liking of asparagus and willingness to pay more for it. — 231 adult subjects in two experiments, suggestion vs control (n = 231) Evidence B source
  Greater general liking, desire to order and willingness to pay for asparagus after the suggestion
• The EU refused the claim that asparagus supports kidney excretion or urine flow, and no asparagus claim is authorized. — EU health claims register, snapshot 2026-09-21 (n = -) Evidence E source
  1 asparagus claim, non-authorized; 0 authorized
• The EU also refused the claim that cruciferous vegetables such as Brussels sprouts protect cells and DNA or help eliminate toxins. — EU health claims register, snapshot 2026-09-21 (n = -) Evidence E source
  Claim non-authorized; 5 sprout-related claims, 0 authorized
• Under the FDA rule updated in December 2024, plain asparagus or Brussels sprouts with nothing added except water automatically qualify for the “healthy” label claim. — US food labeling: the voluntary “healthy” nutrient content claim, 21 CFR 101.65(d) as updated by FDA Evidence E source
  Vegetables with no added ingredients except water qualify automatically; no food-group minimum or nutrient-limit calculation needed

Who this works differently for

• Pooling 23 dietary trials, diets rich in cruciferous vegetables such as Brussels sprouts raised CYP1A2 drug-metabolizing activity by 20 to 40%. — 23 human dietary intervention trials with drug metabolism end points; broccoli, Brussels sprout, cabbage, cauliflower, radish, watercress (n = 23 trials) Evidence B source
  CYP1A2 activity +20-40%; GST-alpha +15-35%
• FDA advises children, older adults, pregnant women and people with weak immunity to avoid raw or lightly cooked sprouts of any kind. — people more vulnerable to foodborne illness: children, older adults, pregnant women, immunocompromised (n = -) Evidence E source
  Avoid raw or lightly cooked onion, alfalfa, clover, radish and mung bean sprouts
• In summer 2026 FDA and CDC traced a US outbreak of E. coli and Salmonella infections to raw alfalfa sprouts: 55 people ill in 15 states, 4 of them hospitalized. — US multistate outbreak, illness onsets May 31 to August 8, 2026; alfalfa sprouts from one grower and the seed lot used to grow them (recalled) (n = 55) Evidence E source
  55 cases (46 E. coli, 7 Salmonella, 2 both), 4 hospitalizations, no deaths; 26 of 34 interviewed (76%) ate alfalfa sprouts
• A second, separate 2026 US outbreak was linked to raw broccoli sprouts: 32 people with Salmonella in six states, 3 hospitalized. — US multistate outbreak of Salmonella Bovismorbificans, illness onsets July 7 to September 3, 2026; recalled broccoli sprouts from one grower (n = 32) Evidence E source
  32 cases, 3 hospitalizations, no deaths; 26 of 27 interviewed (96%) ate sprouts or microgreens, 22 named broccoli sprouts; sprout samples matched the outbreak strain by WGS

The bottom line

The risk from seed sprouts is current. In 2026 FDA and CDC traced two separate US outbreaks to raw sprouts, each from a single grower. Alfalfa sprouts made 55 people ill with E. coli or Salmonella in 15 states, 4 of them hospitalized, by the August update. Broccoli sprouts made 32 people ill with Salmonella in six states, 3 of them hospitalized, by the September update, with the investigation still open. These are outbreak counts and give no rate of illness per serving. The US Food and Drug Administration advises children, older adults, pregnant women and people with weakened immunity to avoid raw or lightly cooked sprouts of any kind, including alfalfa, clover, radish, onion and mung bean sprouts. That advice is about seed sprouts, and Brussels sprouts are a different food. If you take a medicine cleared by CYP1A2, the enzyme effect above is a question for the person prescribing it, since the pooled trials measured enzyme activity and left the clinical meaning open. We have no card on either vegetable with blood thinners such as warfarin, so that question also belongs with the prescriber. Cooking takes a share of the vitamins. By USDA group factors from 1975 data for vegetables in general, boiling in water and draining keeps about 75 percent of vitamin C and 65 percent of folate, and steaming keeps 85 percent of folate. Nobody measured these factors on asparagus or Brussels sprouts. In the US food survey one cooked asparagus spear weighs 16 g and one Brussels sprout 20 g, with a cup at 180 g and 155 g. Data on either vegetable eaten as food is thin. A meta-analysis of prospective cohorts linked each 100 g a day of Brussels sprouts with 25 percent higher risk of hypertension (95% CI 7 to 47 percent) and broccoli with 12 percent lower. That rests on 2 to 5 studies per vegetable, and the authors call the subtype results mixed. In 177,148 UK Biobank adults, a strong liking for asparagus came with 31 percent lower all-cause mortality over 3.4 years, a signal about taste, since intake was never measured. The asparagus trial in 20 healthy men doing supervised resistance training used 30 mg a day of an extract compound, 20-hydroxyecdysone, and found more arm fat loss than placebo over 12 weeks, with no effect size in the abstract. It says nothing about eating the spears, and we have no card on the safety of this compound taken as a supplement. In healthy adults, sulforaphane from fresh broccoli sprouts was absorbed about 3 times better than the same dose from a sprout extract, in a trial whose abstract gives no sample size. The EU refused the claim that asparagus supports the kidneys and the claim that cruciferous vegetables protect cells and help eliminate toxins, and no claim for either vegetable is authorized. In the US, plain asparagus or Brussels sprouts with nothing added but water automatically qualify for the voluntary "healthy" label under the FDA rule of December 2024, a labeling rule that makes no promise about disease.

Sources

1. asbs-daily-r4-01 · reference dataset
   Asparagus, green, raw: Folate, total 182.5 ug (range 143.0-206.6, 8 samples); Vitamin C 9.153 mg (range 5.38-12.4); Fiber, total dietary 1.883 g; Potassium, K 277.5 mg. Brussels sprouts, raw: Folate, total 86.0 ug (range 48.0-140.0, 8 samples); Vitamin C 142.9 mg (range 84.6-197.0); Fiber, total dietary 4.785 g; Potassium, K 476.8 mg per 100 g
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-09-28
2. asbs-daily-r4-02 · reference dataset
   FNDDS 2709834 Asparagus, fresh, cooked, no added fat, code 75202011 - 1 spear 16 g; 1 cup 180 g; Quantity not specified 90 g. FNDDS 2709881 Brussels sprouts, fresh, cooked, no added fat, code 75209011 - 1 sprout 20 g; 1 cup 155 g; Quantity not specified 78 g
   USDA FNDDS via FoodData Central, release 2026-04-30, food codes 75202011 and 75209011 · checked 2026-09-28
3. asbs-daily-r4-08 · randomized controlled trial
   Using HPLC-MS/MS, we detected ∼3 x higher SFN metabolite levels in plasma and urine of sprout consumers, indicating enhanced SFN absorption from sprouts.
   Mol Nutr Food Res, 2015 · checked 2026-09-28
4. asbs-daily-r4-03 · reference 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%. USDA-RETN-R6:3784 VEG,OTHER,STEAMED: folate_total_ug 85%
   USDA Table of Nutrient Retention Factors, Release 6 (2007), USDA-RETN-R6:3775 and 3784 · checked 2026-09-28
5. asbs-daily-r4-05 · meta-analysis of cohorts
   The summary RRs per 100 g/day was 0.81 (95% CI 0.70–0.94, I2 = 50.7%, Pheterogeneity = 0.13) for avocado, 0.88 (95% CI: 0.82-0.94, I2 = 0%, Pheterogeneity = 0.68) for broccoli, 0.90 (95% CI 0.85–0.96, I2 = 0%, Pheterogeneity = 0.98) for carrots, 0.92 (95% CI 0.87–0.98, I2 = 0%, Pheterogeneity = 0.46) for lettuce, 1.25 (95% CI 1.07–1.47, I2 = 20.0%, Pheterogeneity = 0.29) for Brussels sprouts
   Eur J Nutr, 2023 · checked 2026-09-28
6. asbs-daily-r4-06 · prospective cohort
   Higher preference for asparagus (hazard ratio (95% confidence interval)): 0.69 (0.62, 0.77)), aubergine (0.79 (0.72, 0.87)), black pepper (0.72 (0.64, 0.81)), broccoli (0.69 (0.61, 0.79)), butternut squash (0.75 (0.68, 0.83)), and extra virgin olive oil (0.67 (0.58, 0.78)) was linked to lower all-cause mortality
   Sci Rep, 2026 · checked 2026-09-28
7. asbs-daily-r4-07 · randomized controlled trial
   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. ... The 20E group showed significant reductions in arm (p<0.01), leg (p<0.05), and abdominal fat (p<0.05), with arm fat reduction significantly greater than in the PLA group (p<0.05).
   J Nutr Sci Vitaminol (Tokyo), 2025 · checked 2026-09-28
8. asbs-daily-r4-10 · case-control study
   A total of 230 cases (69% female, median age: 48 years) were identified, with 33% requiring hospitalization. ... A matched case-control study found cases to be associated with consumption of sprouts (penalized adjusted odds ratio of 3.13).
   Infection, 2025 · checked 2026-09-28
9. asbs-daily-r4-09 · randomized experiment
   In two experiments, involving 231 subjects, we planted the suggestion that subjects loved to eat asparagus as children. ... These new (false) beliefs had consequences for those who formed them, including increased general liking of asparagus, greater desire to eat asparagus in a restaurant setting, and a willingness to pay more for asparagus in the grocery store.
   Exp Psychol, 2008 · checked 2026-09-28
10. asbs-daily-r4-12 · regulatory register
    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 2026-09-28
11. asbs-daily-r4-13 · 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
12. asbs-webfix-1-01 · US federal regulation (agency explainer page)
    Under the updated ”healthy” claim, nutrient-dense foods that are encouraged by the Dietary Guidelines – vegetables, fruits, whole grains, fat-free and low-fat dairy, lean game meat, seafood, eggs, beans, peas, lentils, nuts, and seeds – with no added ingredients except for water, automatically qualify for the “healthy” claim because of their nutrient profile and positive contribution to an overall healthy diet.
    US FDA, Use of the “Healthy” Claim on Food Labeling (final rule of December 19, 2024) · checked 2026-09-29
13. asbs-daily-r4-04 · meta-analysis of intervention trials
    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 2026-09-28
14. asbs-daily-r4-11 · agency guidance
    People who are more vulnerable to foodborne illness (as identified above) should avoid eating raw or lightly cooked sprouts of any kind (including onion, alfalfa, clover, radish, and mung bean sprouts).
    US FDA, Selecting and Serving Produce Safely · checked 2026-09-28
15. asbs-ws-1-01 · outbreak investigation
    Based on epidemiological information collected by CDC and state partners, a total of 55 people infected with multiple strains of Shiga toxin-producing E. coli and one strain of Salmonella have been reported from 15 states.
    US FDA, Outbreak Investigation of Shiga Toxin-producing E. coli & Salmonella: Sprouts (August 2026) · checked 2026-09-29
16. asbs-ws-1-02 · outbreak investigation
    Based on epidemiological information collected by CDC and state partners, a total of 32 people infected with the outbreak strain of Salmonella have been reported from six states.
    US FDA, Outbreak Investigation of Salmonella: Sprouts (September 2026) · checked 2026-09-29