Most of the green “wasabi” served outside Japan is a stand-in. It is usually a mix of horseradish, mustard, starch and green coloring. Packages are often labeled wasabi even when the ingredients list no part of the plant. Japan has names for both: horseradish is seiyo-wasabi, or “western wasabi”, and the real plant is hon-wasabi.
Real wasabi, Eutrema japonicum, is a rhizome (an underground stem). It grows in cool, clear, flowing water at about 10 to 15 °C and cannot take strong sunlight. That is why it grows in so few places and costs so much.
Grating breaks its cells and forms allyl isothiocyanate, the same pungent compound found in horseradish and mustard. The finer the grating, the sharper the heat. The vapor stings the nose more than the tongue and fades faster than chili heat.
The compound researchers study most is a different one: 6-MSITC (6-methylsulfinylhexyl isothiocyanate). It is a longer-chained relative of broccoli’s sulforaphane. Its amount varies between wasabi strains and with the season. Nearly all the health research below tested supplements or extracts of it, not a dab of paste on a plate.
Health benefits of wasabi
The top findings from 10 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 memory in adults 60 and olderIn 72 healthy adults aged 60 and older, 12 weeks of 6-MSITC, a wasabi compound, improved working memory and memory of events against placebo. Working memory is holding facts in mind; attention and other tests did not clearly improve.
- ★Better sleep and mood, but no placebo groupIn 20 tired volunteers, 4 weeks of wasabi extract with 4.8 mg a day of 6-MSITC went with better sleep and mood. Fatigue before a task improved, but fatigue after a mental task and stress did not change.
- ★Less brain fog in chronic fatigue syndromeIn 15 people with chronic fatigue syndrome, 9.6 mg of 6-MSITC a day for 12 weeks lowered brain fog scores from 5.7 to 4.5. Fatigue scores did not clearly change, and there was no placebo group.
- ★No effect on muscle damage after exerciseIn 8 young men, 9 mg a day of 6-MSITC did not reduce muscle damage or soreness after hard arm exercise. Other markers were similar to placebo too, and the trial was very small.
All 10 studies, strongest evidence first
6-MSITC improved working and episodic memory in adults 60 and older
In this double-blind randomized trial, 72 healthy older adults took a 6-MSITC supplement or a placebo (dummy pill) for 12 weeks. Other areas tested, such as executive function, processing speed and attention, did not clearly improve. The abstract does not give the dose. The trial was supported by the company KINJIRUSHI, which the paper says had no role in the design, analysis or decision to publish.
A wasabi extract improved sleep, mood and pre-task fatigue; no placebo group
In this single-group, open-label trial, 20 tired volunteers took wasabi extract powder with 4.8 mg of 6-MSITC a day for 4 weeks. Fatigue after a mental task, stress, immune markers and autonomic nerve function did not change. A separate double-blind, placebo-controlled safety study in 30 volunteers found no side effects at up to 16 mg a day for 4 weeks. Two authors work for the nutraceutical group of Teijin.
Wasabi extract improved performance status and brain fog, but not fatigue scores
In this open-label trial with no placebo group, 15 people with chronic fatigue syndrome took 9.6 mg of 6-MSITC a day for 12 weeks. Headaches fell from 4.1 to 3.0 times a week and brain fog scores from 5.7 to 4.5. The 11-item Chalder Fatigue scale and the fatigue rating did not clearly change. No serious side effects were reported, and the study was supported by the company PAL.
6-MSITC did not reduce muscle damage or inflammation markers after exercise
In this randomized, double-blind crossover pilot, 8 young men did hard arm exercise and took 9 mg a day of 6-MSITC or a placebo. They took it from 1 day before the exercise to 4 days after. Blood calpain-1, creatine kinase, muscle strength, soreness and the other markers measured were similar to placebo. The trial was very small, so it could miss a modest effect.
Wasabi powder lowered weight, triglycerides and cholesterol in rats on fatty diets
In this animal study, rats ate a high-fat, high-carbohydrate diet for 8 weeks, then half also got wasabi powder for 8 more weeks. The powder (rhizome and stem) made up 5% of their food, and 5% of a diet is far more than a meal holds. These rats weighed 416 g instead of 460 g, and fat mass was 120 g against 178 g. Triglycerides were 0.9 against 1.7 mmol/L and total cholesterol 1.0 against 1.5 mmol/L, and blood pressure and the blood sugar curve fell too.
A wasabi substitute paste killed Anisakis worm larvae in a dish
This lab study used larvae of Anisakis pegreffii, a parasite of raw fish. The commercial paste at 2 and 1 g/mL took 30 and 45 minutes on average to kill them. Allyl isothiocyanate, its main pungent compound, killed half the larvae in 16 minutes. The paste was a substitute product, not grated wasabi, and the test was in a dish, not in fish or people.
Wasabi extract prevented colitis in mice, better when coated for the colon
This lab study gave a wasabi ethanol extract to mice with chemically induced colitis (gut inflammation). The extract blocked the NF-κB inflammation pathway and helped restore the tight junctions (seals) of the gut lining. This was an extract in mice, not wasabi as eaten.
Wasabi extract triggered colon cancer cell death, delayed tumor growth in mice
This lab study used human Colo 205 colon cancer cells, plus mice carrying the human tumor (a xenograft model). The extract set off apoptosis and autophagy, processes in which cells destroy or digest themselves. Cells and mice only, so it says little about what eating wasabi does.
Wasabi was the richest vegetable source of the enzyme inducer 6-MSITC
This lab study screened vegetable extracts in rat liver cells for enzyme-inducing activity. 6-MSITC switches on liver enzymes that break down toxins. In animals it was absorbed quickly and raised these enzymes more than broccoli’s sulforaphane did. The effect disappeared in mice lacking the Nrf2 gene; cells and animals only.
6-MSITC by mouth slowed human breast cancer tumors in mice
This lab study gave 6-MSITC for 12 days to 30 mice carrying human breast cancer cells. Tumor volume was clearly lower on days 9 and 11. In cell tests, the compound triggered apoptosis and dampened NF-κB inflammation signaling. This is an isolated compound in mice.
Who should be careful with wasabi
Most people can eat wasabi freely. Take a little care if one of these applies:
- Mustard allergy. Imitation wasabi pastes are often made with horseradish and mustard. Mustard is one of the 14 allergens that must be declared on food labels in the EU. If you react to mustard, read the label of any tube, powder or sauce.
- Wasabi supplements. The human trials ran 4 to 12 weeks. The only safety test went up to 16 mg a day of 6-MSITC for 4 weeks in 30 volunteers. Longer or higher use has not been studied, and wasabi as a condiment is a much smaller dose.
- Raw fish. Wasabi is a seasoning, not protection. The FDA lists sushi and sashimi among foods linked to fish parasites and says freezing the fish kills them. This concern is about the fish, and it is small when the fish was frozen properly.
How to choose, store and eat wasabi
- Fresh rhizome: grate it just before eating on a fine grater, such as a sharkskin or metal oroshigane. The finer the grating, the sharper the heat. A tablespoon (8.1 g) has 9 calories.
- Tube paste and powder: outside Japan these are usually horseradish-based. Japan’s trade agency notes that tubed paste is processed with other ingredients, including horseradish. Ingredients are listed by weight, so look for Wasabia japonica or Eutrema japonicum near the top.
- Leaves and stems: these are edible too, with a fresh, sharp flavor, and are popular in Japan for pickles.
Real wasabi is generally found only at specialty grocers and high-end restaurants outside Japan, so ask for the rhizome by name. Fresh paste loses its flavor quickly if left uncovered. So grate only what you need, as sushi chefs do, and put it between the fish and the rice to keep its flavor.
Sources
- Wasabi: highlighted Japanese ingredients. Japan External Trade Organization (JETRO).
- Wasabi. Wikipedia.
- List of 14 allergens. Food Safety Authority of Ireland.
- Nakajima R, Kanou M, Tokushima M, Iwama Y, Yamana K. Oral administration of 6-methylsulfinylhexyl isothiocyanate extracted from wasabi is safe and improves the fatigue and sleep of healthy volunteers. Biopsychosoc Med. 2023.
- Sonko P, Chou CM, Hsu SL, Lye LF, Fan CK. Nematocidal activity of wasabi paste and allyl isothiocyanate against Anisakis third-stage larvae and their stress response characterized by heat shock protein expression. J Helminthol. 2025.
- Fish and fishery products hazards and controls guidance, chapter 5: parasites. US Food and Drug Administration.
History of wasabi
Wasabi grows wild along mountain streams in Japan, in the Russian Far East including Sakhalin, and on the Korean Peninsula. A 2026 genome study found it is a hybrid. Two related ancestors that split about 2 million years ago crossed about 268,000 years ago to form today’s plant. It is the only cultivated Eutrema species with a strong pungent flavor.
The oldest record of wasabi as a food dates to the 8th century. Farming came much later: Japan’s trade agency says growers began cultivating it over 400 years ago. Shizuoka and Nagano now grow over 90% of the country’s water wasabi, the type grown in flowing spring water.
Sushi gave wasabi its modern role. It was used long ago to cover fish smells. It came into wider use after hand-rolled sushi appeared in the latter half of the Edo period (1603 to 1867). Japan’s trade agency says this use grew because wasabi was known to remove odor and slow bacteria.
Growers in Izu, in Shizuoka, developed the rock-matting style (tatamiishi) around the mid-Meiji period (1868 to 1912). Shizuoka’s terraced wasabi fields run on spring water rather than fertilizer. In March 2018, the UN Food and Agriculture Organization named them a Globally Important Agricultural Heritage System.
Outside Japan, wasabi’s popularity followed sushi, growing steadily from about 1980. Real wasabi is hard to grow in quantity, so horseradish took its place, and it is still the usual stand-in.
Wasabi also won an Ig Nobel Prize. In 2011, Makoto Imai and colleagues were honored in chemistry for finding how much airborne wasabi wakes a sleeper. The work was for a fire alarm meant for deaf people.
Their patent application describes a spray that releases allyl isothiocyanate. It says 5 to 20 parts per million woke sleeping test subjects.
Sources
- Wasabi: highlighted Japanese ingredients. Japan External Trade Organization (JETRO).
- Wasabi. Wikipedia.
- Jeon D, Lee S, Choi S, Paterson AH, Kim C. Genome stabilization in the neotetraploid wasabi (Eutrema japonicum): subgenome dominance and extensive chromosomal rearrangements. BMC Plant Biol. 2026.
- Yamane K, Yamada-Kato T, Haga N, et al. Allyl isothiocyanate and 6-(methylsulfinyl) hexyl isothiocyanate contents vary among wild and cultivated wasabi (Eutrema japonium). Breed Sci. 2023.
- Jordt SE, Bautista DM, Chuang HH, et al. Mustard oils and cannabinoids excite sensory nerve fibres through the TRP channel ANKTM1. Nature. 2004.
- Morimitsu Y, Nakagawa Y, Hayashi K, et al. A sulforaphane analogue that potently activates the Nrf2-dependent detoxification pathway. J Biol Chem. 2002.
- A look at the wasabi fire alarm (chemistry prize). Improbable Research. 2011.
- Goto H, Sakai T, Mizoguchi K, Tajima Y, Imai M. Odor generation alarm. US patent application 2010/0308995. 2010.
Frequently asked questions about wasabi
Is wasabi good for you?
It may help in small ways, but the evidence is thin. Small trials of a supplement of the wasabi compound 6-MSITC found better memory in 72 adults aged 60 and older. They also found better sleep and mood in 20 tired volunteers, but no effect on muscle damage in 8 men.
A tablespoon (8.1 g) of grated root has 9 calories and 4% of the Daily Value for vitamin C. Most of the green paste in shops is horseradish, which these trials did not test.
What is the difference between wasabi and horseradish?
They are different plants in the same cabbage family. Wasabi is a rhizome that grows in cool mountain streams in Japan. Horseradish is the common, cheaper root that Japan calls “western wasabi”. Both form allyl isothiocyanate when grated, the pungent compound in mustard too.
Outside Japan, most green “wasabi” paste is horseradish, mustard, starch and coloring, so check that the plant is in the ingredient list.
Does wasabi kill parasites in sushi?
Not reliably. In a dish, a commercial wasabi substitute paste took 30 to 45 minutes to kill Anisakis larvae on average. Its main pungent compound killed half in 16 minutes, but that is not fish on a plate.
The FDA says freezing for 7 days at -4°F (-20°C) kills parasites in fish meant to be eaten raw. Other freezing schedules it lists also work. Treat wasabi as seasoning, not protection.
How many calories are in wasabi?
Very few. A tablespoon (8.1 g) of grated wasabi root has 9 calories, 0.4 g of protein and 0.6 g of fiber. That is the real plant. Tube pastes made with horseradish, starch and other ingredients differ, so check the label.
Why does wasabi burn your nose and not your mouth?
The heat comes from allyl isothiocyanate, which forms when wasabi is grated and rises as a vapor into the nose. It switches on a pain sensor called TRPA1 (ANKTM1 in the original paper) on sensory nerves. Mustard oil triggers the same sensor. Capsaicin, the compound that makes chili hot, is a different molecule, and wasabi’s heat fades faster.
Can wasabi make you sick?
Rarely, at the amounts people eat. In the one safety test, 30 volunteers took up to 16 mg a day of 6-MSITC for 4 weeks with no side effects. But that was a supplement. The practical problems are a sharp sting and mustard allergy, because imitation pastes often contain mustard.
Does wasabi help with sinus problems?
No study here tested it. The sudden sting in the nose comes from allyl isothiocyanate irritating sensory nerves, which is a sensation and not a treatment. If you have long-lasting sinus trouble, see a doctor.