Mustard seeds come from three plants in the mustard family: yellow or white (Sinapis alba), brown (Brassica juncea) and black (Brassica nigra). Each seed is only 1 to 2 mm across. The brown and black seeds are hotter than the yellow ones, and none of that heat exists until the seed is crushed.
Crush a mustard seed and mix it with water, and an enzyme called myrosinase turns glucosinolates, mainly sinigrin in black mustard and sinalbin in white mustard, into the sharp isothiocyanates that sting the nose. Hot water or vinegar tames that reaction, which is why mustard made with cold water is hotter. The enzyme also works on other foods. Boiling destroys the enzyme in broccoli, but in a trial of 12 adults, 1 g of powdered brown mustard added to cooked broccoli raised sulforaphane absorption more than fourfold. Our broccoli page has the rest of that story.
A teaspoon of ground mustard seed (2 g) has about 10 calories, 0.5 g of protein and 0.2 g of fiber. Its standout nutrient is selenium: a teaspoon gives 8% of the daily value, and gram for gram no other herb or spice on this site has more. Research on the seed itself in people is thin, and most studies below used mustard in a meal, a powder, an extract or a single compound, so each card says which.
Health benefits of mustard seeds
The top findings from 12 studies, strongest evidence first
What the stars mean
- Strong. Several randomized trials, pooled in a meta-analysis, point the same way, or regulators (FDA or EFSA) have approved the claim.
- Moderate. Good randomized trials support it, but there are fewer of them, or their results vary.
- Limited. Small, short or single trials, or mixed results. Promising, but it needs confirmation.
Population and lab studies get no stars: they show a link or a mechanism, not proof.
How we rate evidence →- ★Better absorption of a broccoli compoundAdding 1 g of powdered brown mustard to cooked broccoli raised a urine marker of sulforaphane more than fourfold in 12 adults. With a broccoli seed extract, mustard seed powder doubled absorption (39.8% against 18.6%).
- ★No clear change in calorie burningIn 11 healthy men, 10 g of mustard did not raise calorie burning. In 22 men, a meal with 21 g of mustard tended to raise it by 14%, but not significantly.
- ★Lower blood sugar after soup with mustard branIn 10 healthy young men, adding 5 g of yellow mustard bran to a soup lowered blood sugar at 15, 30 and 90 minutes. It was tiny and short, and bran is not the whole seed.
- ★Fewer bad-breath gases from a special gumIn 15 healthy adults, gum with a mustard seed compound and zinc cut bad-breath sulfur gases by 89% right after chewing. It was an extract in gum, not the spice.
- Population studyLinked to allergic reactions in some peopleIn a US registry of people with seed or spice allergies, mustard was among the top three non-sesame seed allergens. Of 30 young people with positive skin tests to mustard, 7 reacted in a food challenge.
All 12 studies, strongest evidence first
Adding 1 g of powdered brown mustard to cooked broccoli raised sulforaphane absorption more than fourfold
Randomized crossover trial in 12 healthy adults who ate 200 g of cooked broccoli with or without the mustard seed powder. A urine marker of sulforaphane over 24 hours rose from 9.8 to 44.7 µmol per gram of creatinine, with wide differences between people. It was small and measured a urine marker, not health.
A meal with 21 g of mustard tended to raise calorie burning by 14%, but not significantly
Placebo-controlled, single-blind crossover trial in 22 young, normal-weight men, comparing meals with mustard, black pepper, ginger, horseradish or no spice (P=0.08 for mustard). Appetite, later calorie intake and energy balance did not differ with any spice. The abstract does not say what kind of mustard was used.
Adding 5 g of yellow mustard bran to a soup lowered blood sugar at 15, 30 and 90 minutes
Randomized trial in 10 healthy young men who ate potato and leek soup with or without the bran, the husk-rich part of the seed left after milling. It was tiny, short and in healthy men only, and bran is not the whole seed.
Eating 10 g of mustard did not raise calorie burning in 11 healthy men
Crossover trial comparing mustard in capsules, mustard without capsules and a placebo, with energy burned, body temperature, hunger and blood markers checked over 150 minutes. None differed. In mice, an injection of the pungent compound allyl isothiocyanate raised energy use by 32%, and 10 g was the highest dose the men could tolerate.
Mustard seed powder doubled the sulforaphane absorbed from a broccoli seed extract
Randomized, double-blind crossover trial in 16 people who took one dose of broccoli seed extract with or without mustard seed powder. Absorption was 39.8% with the powder and 18.6% without. This was a supplement-type extract, not broccoli, and a single dose. One author worked for a company that sells broccoli seed products, and another was a consultant to it.
Chewing gum with a mustard seed compound cut bad-breath sulfur gases by 89% right after chewing
Trial in 15 healthy adults who chewed a gum with 0.01% allyl isothiocyanate from mustard seed extract and 0.1% zinc lactate, or a placebo gum, for 12 minutes. The drop was 55.5% after 1 hour, 48% after 2 hours and 24% after 3 hours. It was a small trial of an extract in gum, not the spice, and zinc was part of the gum.
In a US registry of 2,601 people with allergy to sesame, other seeds or herbs and spices, mustard was among the top three non-sesame seed allergens
Survey data from the Food Allergy Research & Education registry, based on what patients reported. Sunflower, mustard and flaxseed led the non-sesame seeds. Across all these foods, about 80% were diagnosed before age 18 and epinephrine was used in about a third of reactions. It does not say how many people in the population are allergic to mustard.
In 24 patients with mustard allergy, a blinded food challenge caused symptoms in 14 (58.3%)
Prospective study of 38 mostly adult patients with mustard allergy compared with matched controls. 10.5% reported anaphylaxis, 97.4% were also sensitized to mugwort pollen, and all were sensitized to other mustard-family foods. It studied people who were already allergic, so it cannot show how common the allergy is.
Of 30 young people with positive skin tests to mustard, 7 reacted in a food challenge
Prospective study of people aged 3 to 20 who tested positive to ground mustard seeds, mustard flour or mustard seasoning, then ate up to 1,340 mg of mustard seasoning in blinded challenges. About 23.3% were truly allergic, and skin tests and blood IgE did not predict who reacted. The authors note mustard allergy makes up 1.1% of food allergies in children.
Powdered white mustard seed added to boiled broccoli restored the sulforaphane that boiling had stopped
Lab study of broccoli cooked in water or in sealed bags (sous vide) at 100°C for 8 and 12 minutes, with powdered mustard seed added afterward. Less than 12% of the glucoraphanin was lost to heat, but boiling destroyed broccoli’s own enzyme, and mustard seed brought a more heat-resistant one. No people were tested here; the human trial above followed it.
A powder of mustard seed and broccoli sprouts curbed weight gain in obese mice
Cell and mouse study of obesity induced by bisphenol A. The mix of mustard seed powder and broccoli sprout powder curbed weight gain slightly more than sprout powder alone. Mustard seed powder served as the enzyme source to make sulforaphane, and the abstract credits the sprout powder and the mix, not the mustard powder on its own. Not tested in people.
A carbon dioxide extract of yellow mustard seed cut total cholesterol by 49% in rats given a cholesterol-raising drug
Rats got the extract at 550, 175 or 55 mg per kg. On day 21 the top dose cut total cholesterol by 49%, close to the 51% drop with atorvastatin, and the extract blocked a liver enzyme, HMG-CoA reductase, that makes cholesterol. This was a concentrated extract in animals, not seeds in a meal.
Who should be careful with mustard seeds
Most people can eat mustard seeds freely. Take a little care if one of these applies:
- Mustard allergy. Mustard is one of the 14 allergens that must be declared on food labels in the UK and EU, and the rule covers every type of mustard. Reactions can be serious: 10.5% of 38 allergic patients in one study reported anaphylaxis. If you are allergic, avoid whole seeds, powder, prepared mustard and foods that list mustard.
- Erucic acid in large amounts. Mustard seed contains erucic acid, a fat that EFSA limits to 7 mg per kg of body weight a day because of reversible heart effects in animals. Our nutrition data estimate about 190 mg in a teaspoon of ground seed, which is small next to the limit for an adult (about 490 mg at 70 kg) but worth keeping modest for young children.
How to choose, store and eat mustard seeds
- Whole seeds: in South Asian cooking they are usually fried in hot oil until they pop, then stirred into the dish.
- Ground and wet: mixed with cold water and left for about ten minutes, ground seed makes the hottest paste, while hot water or vinegar gives a milder one.
- On cooked broccoli: 1 g of powdered brown mustard raised sulforaphane absorption more than fourfold in 12 adults, so add a pinch after cooking.
Yellow seeds are the mildest, and brown and black are hotter. Keep seeds whole in a sealed jar in a cool, dark place and crush them only when you need them, because the pungent reaction starts only when they are crushed and wet. Check labels if you avoid mustard, since it must be declared on pre-packed food in the UK and EU.
Sources
- Food allergen labelling and information requirements technical guidance. Food Standards Agency.
- Regulation (EU) No 1169/2011 on the provision of food information to consumers, Annex II. European Union.
- Figueroa J, Blanco C, Dumpiérrez AG, et al. Mustard allergy confirmed by double-blind placebo-controlled food challenges: clinical features and cross-reactivity with mugwort pollen and plant-derived foods. Allergy. 2005.
- Erucic acid a possible health risk for highly exposed children. European Food Safety Authority. 2016.
- Lietzow J. Biologically active compounds in mustard seeds: a toxicological perspective. Foods. 2021.
- Spices, mustard seed, ground (FDC ID 170929). USDA FoodData Central.
- Okunade O, Niranjan K, Ghawi SK, Kuhnle G, Methven L. Supplementation of the diet by exogenous myrosinase via mustard seeds to increase the bioavailability of sulforaphane in healthy human subjects after the consumption of cooked broccoli. Mol Nutr Food Res. 2018.
- Mustard seed. Wikipedia.
- Mustard (condiment). Wikipedia.
History of mustard seeds
Mustard is one of the oldest seasonings found by archaeologists. At Jerf el Ahmar, a Neolithic site in Syria, ground seeds of the genus Sinapis turned up in a seed cake dated to between about 9224 and 8753 BC. Finds like this are rare, because mustard-family plants do not form the tiny silica particles, called phytoliths, that archaeologists often rely on.
Brown mustard has a long family tree of its own. A genome study of 480 plants from around the world concluded that brown mustard arose once in West Asia, 8,000 to 14,000 years ago, when two species hybridized naturally. It then spread east along three routes, and different types were selected for greens, oil and seed.
The Romans ground the seeds and mixed them with unfermented grape juice, called must, into a paste known as mustum ardens, burning must. That is where the English word comes from, through Old French mostarde. A recipe in the Roman cookbook De re coquinaria blends mustard with pepper, caraway, honey, vinegar and fish sauce as a glaze for roast boar.
French monks in Paris were making mustard by the 10th century, and Dijon was a recognized mustard center by the 13th. Written accounts of a gala held by the Duke of Burgundy in 1336 describe guests eating 320 liters of mustard cream in one sitting. In England, a 1390 cookbook describes mustard balls of coarse-ground seed, flour and cinnamon that stored well and were mixed with vinegar or wine when needed. Yellow American mustard is said to have been introduced to the public at the 1904 St. Louis World’s Fair.
The seed is also a symbol of smallness. The Parable of the Mustard Seed in the Bible uses it as the smallest of seeds that grows into a large plant, and a story about the Buddha has a grieving mother search for mustard seeds from a house that has never known a death.
Sources
- Mustard (condiment). Wikipedia.
- Mustard seed. Wikipedia.
- Mustard plant. Wikipedia.
- Kang L, Qian L, Zheng M, et al. Genomic insights into the origin, domestication and diversification of Brassica juncea. Nat Genet. 2021.
Frequently asked questions about mustard seeds
Are mustard seeds good for you?
They are a fine seasoning with some nutrients, but no study here proves a health benefit. A teaspoon of ground seed (2 g) has about 10 calories, 0.5 g of protein, 0.2 g of fiber and 8% of the daily value for selenium. The human trials are small, and the cholesterol and weight results come from rats and mice.
What is the difference between yellow, brown and black mustard seeds?
They come from different plants and differ in heat. Yellow (white) mustard is Sinapis alba and is the mildest, while brown (Brassica juncea) and black (Brassica nigra) are hotter. White mustard holds mainly sinalbin and black mustard mainly sinigrin, and they form different pungent compounds when crushed and wet.
Can you eat mustard seeds raw?
Yes, people do, but whole raw seeds are sharp and bitter, and ground seed gets hotter once it meets water. In South Asian cooking the seeds are usually fried in oil until they pop. In one trial, 11 men took 10 g of mustard, in capsules or not, and that was the highest dose they could tolerate, so it is a lot to eat at once.
Does mustard powder make broccoli healthier?
It can make cooked broccoli give you more sulforaphane. Boiling destroys broccoli’s own enzyme, and in 12 adults 1 g of powdered brown mustard raised sulforaphane absorption from 200 g of cooked broccoli more than fourfold. That is a urine marker in a small trial, so it shows the compound is absorbed, not that your health improves.
Are mustard seeds a common allergen?
Mustard is one of the 14 allergens that must be labeled in the UK and EU, and reactions can be serious. In a US registry of 2,601 people allergic to seeds or spices, mustard was among the top three non-sesame seed allergens. In one study of 30 young people with positive skin tests, 7 reacted in a food challenge.
Do mustard seeds help with weight loss or blood sugar?
The evidence is weak. In a trial of 22 men, a meal with 21 g of mustard tended to raise calorie burning by 14%, but not significantly, and 10 g of mustard did nothing in 11 men. Yellow mustard bran (5 g) lowered blood sugar after a soup in 10 young men, but bran is not the whole seed and the trial was tiny.
How many calories are in a teaspoon of mustard seeds?
About 10 calories. A teaspoon of ground mustard seed (2 g) also has 0.5 g of protein, 0.7 g of fat and 0.2 g of fiber. Prepared mustard condiment has about 5 calories a teaspoon, because it is mostly liquid.