I've been to many sushi places and last night I went to a place that I've been to before (not that long ago either). When the sushi came, we noticed that it had wasabi spread on the rice, under the fish.

When we complained we were rudely told that the chef had been doing sushi for 30 years and wasabi is used to kill parasites in the fish.

This is believable since I know in some countries, red peppers are used in foods all the time for the same reason.

However, my understanding of sushi is that the chef is a craftsman who not only picks great fish, but also knows how to find and remove parasites.

My question is, is this normal? Is it proper for the Sushi chef to add wasabi to the sushi to help prevent parasites? If so, how come I've only encountered this practice once out of the many sushi places I've frequented?

  • 9
    Wasabi is placed under fish ontop of rice to hold the fish in place. Parasites are killed when the fish is flash frozen on the boat it was caught on.
    – D3vtr0n
    Commented Nov 8, 2012 at 20:55

6 Answers 6


This is perfectly normal, however, I find the common claim that "it is to prevent parasites" a bit dubious (I would think that it would have to be uniformly applied to the entire fish to have any measurable effect). The wasabi is really there to add flavor. In really high-end sushi restaurants in Japan, for example, it is relatively uncommon for the guest to be served a mound of grated wasabi. Instead, the chef applies the perfect amount of wasabi to each piece of sushi. Some chefs will not even serve soy sauce, instead individually brushing on the sauce on each piece. If wasabi is served separately from the fish, it is generally also considered bad form to mix it with the soy sauce (as is commonly done in the US).

Edit: To answer your question about why you've never seen this practice before, here are some possible explanations:

  1. It takes more time/skill/effort to do it properly.
  2. Many sushi restaurants in the US do not have properly trained sushi chefs. In fact, in most areas of the country with little or no Japanese population, don't be surprised if your sushi chef is a Salvadorian who learned from the Oaxacan who learned from the Korean owner of the restaurant. Not that there's anything wrong with that; one of my favorite sushi places is run by an Indonesian. Just keep in mind that the people making you your sushi may have never experienced the "real thing" themselves.
  3. "Real," fresh wasabi is very rare and expensive. Most of the stuff that is used in the US is basically horseradish paste plus food coloring. Restaurants that can both procure and afford to use the real stuff will want to use it sparingly; they wouldn't want to waste it by putting a mound of it on each plate. Therefore, they might be more inclined to use the "proper" technique.

Edit 2: Here is a video in which you can see famous chef Naomichi Yasuda using wasabi in the sushi. It all happens very quickly, but you can clearly see him dip into the bin of wasabi, rub it on the underside of the fish, and then apply the fish to the rice. Here is another video in which Anthony Bourdain explains the "rules" of high-end sushi eating, while dining at the super-famous and super-expensive Sukiyabashi Jiro (the proprietor of which is actually designated as a "living treasure" by the Japanese government). That second video shows the chef brushing on the soy sauce, and the general lack of both soy and wasabi on the plates.

  • 5
    Ah I understand it, one isn't supposed to eat sushi with chopsticks either. It's like eating a taco with knife and fork. Commented Aug 2, 2011 at 22:48
  • 2
    +1 for comment 2. This is a global problem. Lack of real training and therefore people making bad examples of classic foods
    – TFD
    Commented Aug 2, 2011 at 23:13
  • 8
    @SevenSidedDie: well, there's worst... you could eat sushi with knife and fork!!! :D
    – nico
    Commented Aug 3, 2011 at 7:00
  • 8
    When I lived in Japan, it was quite common to mix wasabi with soy sauce when it was served separately. It was also normal to eat sushi with chopsticks. Apparently both of these practices are not truly "correct," but a quick search online shows many Japanese having the same doubts about proper eating sushi etiquette, so don't imagine you are causing a major faux pas as many Japanese themselves seem to be unsure of these points.
    – user1570
    Commented Aug 3, 2011 at 7:43
  • 3
    @user1570: That's right. I think it really depends on the formality of the restaurant. In the more formal places, they won't serve any separate wasabi or soy (only gari) and they'll give you a small moist towel (in addition to the oshibori) that you are supposed to use to clean your fingers between pieces of sushi, under the expectation that you will use your hands. If they don't give a towel to clean your fingers, then I think it is acceptable to use chopsticks.
    – ESultanik
    Commented Aug 3, 2011 at 11:52

The "parasites" claim is quite dubious, and probably mostly folklore, but there has been some published evidence that wasabi slows growth of certain bacteria, including e coli.

http://sciencelinks.jp/j-east/article/200210/000020021002A0124150.php has an abstract of one such study. I've heard the same claim from a book written in the late 80s, so I'm sure it's a widespread belief, but I don't know how long ago the research started. I'm fairly certain that the use of wasabi predates the belief and the research, however.

Most of the commercial wasabi contains a high percentage of mustard, which is the source of most people's sensation that wasabi is "spicy". Coincidentally, mustard is also associated with antibacterial properties. Having eaten a couple of decently-sized wasabi rhizomes in one sitting with fresh soba, I'd say "pungency" is the primary quality of fresh wasabi, and it's a different sensation than mustard. It has a very "clean" taste, which may reinforce people's impressions that it kills bad things.

As ESultanik pointed out, adding wasabi during preparation of the fish is done for flavor, but it has one other side benefit, though this may also be part folklore: The fish is more likely to stay attached to the rice with a dab of wasabi than without. I suspect if you noticed it it was probably sloppily applied, but if you haven't noticed it before, it's quite possible it was just used in sensible moderation.

  • +1 That's a good point. The part that I am skeptical about, though, is whether the small amount of wasabi is actually enough to have any sort of measurable effect.
    – ESultanik
    Commented Aug 4, 2011 at 15:52

Looking at several sources the general way to deal with most parasites is by freezing.

Here is some general information:


More details are here:



The chef's claim is false: Usually, the only side where wasabi is applied is under the fish, so it doesn't slide off the rice.


It should be noted that 95% of wasabi used when serving sushi is not real wasabi, but mustard with green food coloring. True wasabi japonica, is one of the most expensive plant to cultivate and grow. And only real freshly grated wasabi, served in some high-end authentic sushi restaurants, is capable of killing some nematode parasites and bacteria.

  • Thought it was horseradish, not mustard -- but either way, it isn't wasabi :)
    – Erica
    Commented May 13, 2017 at 17:24
  • Are there any references to support the anti-bacteria and anti-nematodes assertion?
    – user110084
    Commented May 13, 2017 at 19:50

Actually used to kill strains of bacteria. Most use it to kill ecoli on the preparation items

  • Hello Allen, do you have a source for such a bold claim? Standard food safety practices don't include the use of wasabi.
    – rumtscho
    Commented Dec 23, 2015 at 10:13
  • @rumtscho he might not ... but JasonTrue does in his answer. (well, for the first sentence of Allen's answer, at least). And you could've just converted this to a comment on the question.
    – Joe
    Commented Dec 14, 2016 at 15:13
  • @Joe I don't see how it would be a comment, its purpose seems to be to answer the question.
    – rumtscho
    Commented Dec 14, 2016 at 17:00
  • @rumtscho : strange, because Divi also mentions it should be a comment.
    – Joe
    Commented Dec 14, 2016 at 17:24
  • Divi used a canned text from the review, and besides, there are a lot of users who think "this is short, so it must be a comment". This is not comments are, in fact there is a network-wide effort to prevent people to leave a short answer in the comment field when they don't feel like writing it up for whatever reason. We have been a bit inconsistent in deleting those here on cooking, but creating them ourselves is certainly not what we want to do.
    – rumtscho
    Commented Dec 14, 2016 at 17:32

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