Mustard seed: a pinch that changes what broccoli gives you

A small amount of mustard changes what cooked broccoli delivers. In a randomized crossover trial in 12 healthy adults, adding 1 g of powdered brown mustard to 7.1 oz (200 g) of cooked broccoli raised the sulforaphane metabolite in urine from 9.8 to 44.7 micromoles per gram of creatinine, about 4.5-fold, after a single meal. A 2026 crossover trial in 16 healthy adults found the same direction using capsules. Taking 145 mg of white mustard seed powder with a broccoli seed extract doubled conversion to sulforaphane, from 18.6% to 39.8% of the dose. Both trials measured how much sulforaphane reached the body, and neither measured a health outcome. By one USDA record with no range, ground mustard seed holds 208 micrograms of selenium and 370 mg of magnesium per 3.5 oz (100 g). Those figures are per 3.5 oz (100 g), far more seed than any dish uses, and we found no standard portion weight for mustard seed. Mustard is also a real food allergen, and in the US it does not have to be labeled as a major allergen.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• USDA lists ground mustard seed at about 208 ug selenium, 370 mg magnesium and 0.65 mg copper per 3.5 oz (100 g). — one USDA SR Legacy record Evidence E source
  Per 100 g: selenium 208.1 ug (378% DV); magnesium 370 mg (88% DV); copper 0.645 mg (72% DV)
• UK food tables list mustard seeds at 28.8 g fat, 24.9 g protein, 520 mg calcium and 18.5 mg iron per 3.5 oz (100 g), with copper 36% lower than the USDA value. — CoFID record 13-839 Mustard seeds Evidence E source
  Per 100 g: fat 28.8 g; protein 24.9 g; calcium 520 mg; iron 18.5 mg; magnesium 300 mg (USDA 370); copper 0.41 mg (USDA 0.645)

What your body absorbs

• In a 2026 crossover RCT in 16 adults, 145 mg of white mustard seed powder doubled conversion of broccoli seed glucoraphanin to sulforaphane, from 18.6% to 39.8%. — sixteen healthy volunteers (9 females and 7 males), 25 to 65 years (n = 16) Evidence B source
  24-h conversion 18.6 +/- 3.1% without vs 39.8 +/- 3.1% with mustard seed myrosinase, p = 0.0016

What cooking and storage change

• In 12 adults, adding 1 g of powdered brown mustard to 200 g cooked broccoli raised sulforaphane uptake about 4.5-fold. — 12 healthy adults, single meals in randomized crossover design (n = 12) Evidence B source
  Urinary SF-NAC 9.8 +/- 5.1 vs 44.7 +/- 33.9 umol per g creatinine

What it does to your health

• In 22 young men, a meal with 21 g mustard raised post-meal energy expenditure by 14% versus placebo, a non-significant trend, with no change in appetite or intake. — twenty-two young normal-weight males (n = 22) Evidence B source
  DIT 59 (SE 3) vs 52 (SE 2) kJ/h, +14%, P=0.08; appetite P>0.85; ad libitum EI P=0.63
• In 10 healthy young men, adding 5 g of yellow mustard bran to a potato and leek soup lowered blood glucose at 15, 30 and 90 minutes. — Ten healthy, non-smoking, moderately active male subjects (n = 10) Evidence B source
  Blood glucose significantly lower at 15, 30 and 90 min (p < 0.0001, p < 0.0001, p = 0.0059)
• In 15 volunteers, gum with 0.01% allyl isothiocyanate from mustard seed and zinc cut mouth-odor sulfur compounds by 89% right after chewing and 24% at 3 hours. — 15 healthy volunteers between the ages of 20-50 (n = 15) Evidence B source
  VSC reduction 89%, 55.5%, 48% and 24% immediately and at 1, 2 and 3 h
• In young soccer players, 8.5 fl oz (250 mL) a day of hardaliye, a grape drink fermented with mustard seeds, for 28 days lowered oxidative stress markers and systolic pressure but not lipids. — young elite soccer players, 28 days Evidence B source
  TAC up, TOS, OSI, MDA and NO down vs placebo (p < 0.05); systolic BP lower; lipids unchanged

Safety, limits and interactions

• A case report describes recurrent hives and swelling in a young woman after eating mustard and mayonnaise, with IgE allergy to mustard seeds confirmed. — A young woman (n = 1) Evidence D source
  Recurrent urticaria and angioneurotic edema; IgE confirmed by RAST

Who this works differently for

• Among 30 children and young people sensitized to mustard, food challenges confirmed true mustard allergy in about 23%, and skin tests did not predict it. — 30 subjects aged 3-20 years presenting positive prick tests to mustard (n = 30) Evidence C source
  7 of 30 challenges positive (23.3%); prick tests and specific IgE not predictive
• A 2026 US case report describes anaphylaxis to mustard in a 23-month-old boy and notes that US law does not require mustard to be labeled as a major allergen. — a 23-month-old male with IgE-mediated egg allergy (n = 1) Evidence D source
  Urticaria, lip swelling and cough within minutes; resolved with epinephrine; prick wheal 15 mm

The bottom line

UK food tables give mustard seeds 28.8 g fat, 24.9 g protein, 520 mg calcium and 18.5 mg iron per 3.5 oz (100 g). Their copper figure, 0.41 mg, is 36% below the USDA value of 0.65 mg, and their magnesium is 300 mg against 370 mg. These are two independent measurements that do not agree, likely from variety or method. We found no USDA portion weight for mustard seed, and no data on how roasting or frying the seeds in oil changes their nutrients. The remaining trials are small and short. In 22 young normal-weight men, a meal with 21 g of mustard condiment raised energy burned after eating by 14%, 59 against 52 kJ per hour, a trend that did not reach significance (P = 0.08). Appetite and later food intake did not change. In 10 healthy young men, 5 g of yellow mustard bran stirred into a potato and leek soup lowered blood glucose at 15, 30 and 90 minutes after one meal. That trial used bran, and whole seed was not tested. Chewing gum with 0.01% allyl isothiocyanate from mustard seed plus zinc cut mouth-odor sulfur compounds in 15 volunteers by 89% straight after chewing and by 24% at 3 hours, and the zinc means the effect cannot be credited to mustard alone. Young elite soccer players who drank 8.5 fl oz (250 mL) a day of hardaliye, a grape drink fermented with mustard seeds and sour cherry leaves, for 28 days had lower oxidative stress markers and systolic pressure than on placebo, with lipids unchanged. Mustard seed is only one ingredient of that drink, and the abstract does not say how many players took part. Who should be careful. Mustard is a real allergen. Among 30 French children and young people aged 3 to 20 with positive skin tests to mustard, food challenges confirmed allergy in 7, about 23%, in a non-randomized study of a group already sensitized. Neither skin tests nor IgE blood tests predicted who would react. A 2026 US report describes anaphylaxis within minutes of mustard in a 23-month-old boy with egg allergy, treated with epinephrine. Its authors note that mustard hides in condiments, sauces and processed foods, and that US law does not require it to be labeled as a major allergen. An older single report describes recurrent hives and swelling in a young woman after mustard and mayonnaise, with IgE allergy to mustard seeds confirmed.

Sources

1. mstr8-10 · USDA FoodData Central SR Legacy, dataset
   Spices, mustard seed, ground (FDC 170929, SR Legacy, Spices and Herbs): selenium 208.1 ug per 100 g = 378% DV; magnesium 370 mg = 88% DV; copper 0.645 mg = 72% DV
   USDA FoodData Central, SR Legacy (2018), FDC 170929 · checked 2026-10-03
2. mstr8-11 · CoFID 2021, dataset
   13-839 Mustard seeds: fat 28.8 g; protein 24.9 g; calcium 520 mg; iron 18.50 mg; magnesium 300 mg; copper 0.41 mg; zinc 4.7 mg
   CoFID 2021, Public Health England, code 13-839 (OGL v3.0) · checked 2026-10-03
3. mstr8-02 · randomized crossover trial
   The combination of BSE and mustard seed powder containing active Myr (GR + Myr), on average, doubled bioavailability of GR to SF and SF metabolites as a percent of the 115 µmol (50 mg) GR dose: from 18.6 ± 3.1% (range 2.2–38.1%) without myrosinase to 39.8 ± 3.1% (range 5.3–76.9%) with exogenous Myr from mustard seed (11.30, df = 1, 43, p = 0.0016) (Fig. 3A).
   Scientific Reports, 2026 · checked 2026-10-03
4. mstr8-01 · randomized crossover trial
   The concentration of sulforaphane metabolite (sulforaphane N-acetyl-l-cysteine [SF-NAC]) in 12 healthy adults after the consumption of 200 g cooked broccoli, with and without 1 g powdered brown mustard, was studied in a randomized crossover design. ... 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 2026-10-03
5. mstr8-03 · randomized crossover trial
   No significant treatment effects were observed on DIT, but mustard produced DIT, which tended to be larger than that of placebo (14 %, 59 (SE 3) v. 52 (SE 2) kJ/h, respectively, P=0·08).
   Br J Nutr, 2013 · checked 2026-10-03
6. mstr8-04 · randomized crossover trial
   Mean blood glucose values at 15, 30 and 90 min (p < 0.0001, p < 0.0001 and p = 0.0059, respectively) were all significantly lower with the addition of 5 g of yellow mustard bran.
   Int J Food Sci Nutr, 2013 · checked 2026-10-03
7. mstr8-05 · randomized crossover trial
   Chewing gum containing 0.1% zinc lactate and 0.01% of allyl isothiocyanate eliminated 89%, 55.5%, 48% and 24% of the total VSC concentration immediately after chewing and at 1, 2, and 3 hours after chewing, respectively.
   Am J Dent, 2013 · checked 2026-10-03
8. mstr8-06 · RCT
   Hardaliye is mainly produced through the fermentation of grapes, sour cherry leaves, and mustard seeds and is consumed as a drink. ... In this single-blind, randomized, placebo-controlled, parallel-design study, while the participants in one of the groups consumed 250 mL/d of hardaliye drink (Hardaliye Group), the participants in the other group consumed placebo drink (Placebo Group) for 28 days. ... Hardaliye consumption significantly decreased systolic blood pressure compared to that in the Placebo Group (p < 0.05).
   J Am Nutr Assoc, 2024 · checked 2026-10-03
9. mstr8-09 · case report
   A young woman had recurrent urticaria and angioneurotic edema following ingestion of mustard and mayonnaise. IgE-mediated allergy to mustard seeds and seeds of botanically related plants was confirmed by RAST.
   Acta Derm Venereol, 1986 · checked 2026-10-03
10. mstr8-07 · food challenge study
    A prospective study was conducted in 30 subjects aged 3-20 years presenting positive prick tests to ground mustard seeds (Brassica nigra), mustard flour (B. juncea), metabisulfite-free strong mustard seasoning (B. juncea) and a commercialized allergenic extract (B. nigra). ... CONCLUSIONS: About 23.3% of the sensitized subjects were allergic to a routine dose of mustard. Positive prick tests and the presence of specific IgE were not predictive.
    Allergy, 2003 · checked 2026-10-03
11. mstr8-08 · case report
    Mustard is frequently present as a hidden ingredient in condiments, sauces, and processed foods and is not currently required to be disclosed as a major allergen under the United States Food Allergen Labeling and Consumer Protection Act (FALCPA). We report a case of mustard-induced anaphylaxis in a 23-month-old male baby with a history of IgE-mediated egg allergy who developed diffuse urticaria, lip swelling, circumoral discoloration, and cough within minutes of isolated mustard exposure.
    Cureus, 2026 · checked 2026-10-03