Why Does Japanese Food Give Me Diarrhea?

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Japanese food is, without a doubt, delicious and nutritious.

But if you’re anything like a lot of people, you may have noticed that this cuisine upsets your stomach and you end up rushing to the toilet shortly after your meal. 

Japanese food stomach problems reasons
Japanese food stomach problems

But why does Japanese food give you diarrhea?

Is it something to do with the ingredients or the way the food is cooked?

Or are you just unlucky?

Nobody Wants Upset stomach shortly after eating

There is no hard and fast evidence as to why Japanese food upsets the stomach.

However, a lot of theories are going around that include eating raw foods, such as sushi as well as an allergic reaction to something like rice. 

Upset stomach shortly after Japanese food solution
Upset stomach shortly after eating Japanese food

Nobody wants to have to grace the throne after enjoying a delicious Japanese meal.

Maybe if we can better understand the possible causes, we can avoid that explosive diarrhea we’ve all experienced after a taste of Japan!

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Raw Fish – Sushi And Sashimi

Perhaps some of the most famous dishes from Japanese cuisine are sushi and sashimi.

Most people think that sushi contains raw fish and that this could be the main reason for getting a sour stomach after eating it. 

Types of Sashimi list
Types of Sashimi

But it’ll probably surprise you when I tell you that sushi is just the rice rolls soaked in vinegar and doesn’t traditionally contain any raw fish ingredients.

However, many sushis are decorated with raw ingredients including fish, eggs, and vegetables. 

On the Other Hand – Sashimi does contain raw fish. This dish contains thin slices of raw foods including fish. 

The problem with eating raw fish is that it comes with a risk of also interesting bacteria or parasites that can upset the digestive system.

Amber Jack nigiri sushi types
Amber Jack nigiri sushi

Here are some of the potential things you may end up eating when taking sushi or sashimi that contains raw fish. 

  • Anisakiasis is a type of roundworm often found in raw fish. When ingested, you may experience several symptoms including diarrhea as well as stomach pain, vomiting and nausea. This usually happens within a couple of hours after eating. Usually the worms will be vomited out but if they aren’t, there is a risk of complications should they bury into the intestinal walls. Most of the time, your immune system will fight them off but sometimes, medical intervention is needed. 
  • Vibrio is a type of bacteria that can be ingested via raw fish or oysters. One of the main symptoms is diarrhea but you may also experience vomiting, stomach cramps, headaches, and fever. Most people will find that the symptoms pass without too many problems but for those with a weakened immune system, vibrio can cause potentially fatal symptoms.
  • Salmonella is a well known bacteria that can cause digestive issues such as vomiting and diarrhea. Most people will recover easily from the bacteria but some may require hospital treatment. 
  • Listeriosis is a bacteria that’s commonly found in uncooked foods like fish and vegetables. In most cases, the symptoms will be mild but may include diarrhea and other forms of digestive upset. However, for pregnant women, elderly adults, and infants, the results of ingesting the bacteria could be a lot more serious and may even cause meningitis. 


Upset stomach after wasabi

Wasabi is a common ingredient in Japanese food and may be the cause of those loose poops after enjoying your meal. 

The problem with wasabi is that it is a spicy condiment and for some people, this just doesn’t agree with them.

If you notice that your stomach plays up whenever you eat spicy food, the wasabi could be to blame. Try leaving it out next time to see if it makes a difference. 

Rice Allergy

Rice allergies are not all that common but some people may have one without even realizing it.

Similar to a gluten intolerance, those with rice intolerance or allergies will react to the protein in rice which can cause a wide range of symptoms, depending on the individual. 

Eating natto with rice
Natto rice

Some people will experience stomach pain and cramps while others may suffer with diarrhea.

In Severe Cases – A rice allergy may also result in difficulty breathing and can be fatal if left untreated.

However, most people have a mild intolerance which could be the reason that they find themselves running to the bathroom after Japanese food. 

Also keep in mind that there is a bacteria known as bacillus cereus which is associated with eating contaminated rice.

In this case, any diarrhea will likely be accompanied by vomiting. 

Miso Soup

Anyone who enjoys Japanese food will have indulged in some miso soup.

But this can be one of the most common causes for diarrhea after eating Japanese food. 

However, this isn’t because of some nasty bacteria or a food allergy. In fact, how miso soup causes diarrhea could be considered beneficial. 

Miso ramen soup
Miso ramen

You see, miso soup contains a probiotic called koji which naturally gets your gut moving and is great if you’re after a cleanse!

Additionally – Miso soup has ingredients packed with fiber such as soybeans as well as copious amounts of salt. Both of which are known for speeding things up down there. 

Inside your gut, there is, or should be, a balance of good and bad bacteria.

But if things are slightly out of balance before you chow down on a bowl of miso soup, there’s a good chance you’ll find yourself heading in the direction of the nearest bathroom. 


If you notice that your stomach starts making funny noises and you can’t hold it in without running to the toilet after eating Japanese food then you aren’t alone. 

A lot of people report bouts of diarrhea after a Japanese dish and there could be several reasons for this.

It may be related to bacteria in raw foods like fish, or could be ingredients that naturally speed up the gut.

In some rare cases, the condition could be caused by an allergy to something like rice but in most cases, the diarrhea isn’t a sign of anything serious.

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