Hidden Risk in Your Sushi Revealed


Hidden Risk in Your Sushi Revealed

Apr 26, 2015 //

Americans love sushi, and our sushi consumption has risen more than 28% since 2010. One of the reasons for the rise in popularity of this Japanese cuisine is its reputation as a “healthy” food option. With so many people regularly enjoying rolls and raw fish, is there any risk of eating sushi?


Sashimi is thinly sliced raw meat such as tuna or salmon served without rice. Sashimi is always served raw, and is never cooked. Sushi is a vinegared rice dish that may or may not contain raw fish. Both of these dishes are commonly ordered at sushi restaurants. It is the presence of raw fish that brings up the first possible sushi risk: parasites.

Sushi is often prepared from fish such as tuna, yellow tail, red snapper, salmon and flounder. Salmon in particular is a known host for a variety of fish tapeworm known as Diphyllobothrium latum. Other varieties of marine fish can also play host to Anisakis parasite larvae.

The FDA requires that all fish that will be served raw in the U.S. be frozen at temperatures low enough to kill parasites. Sushi restaurants freeze all fish (with the exception of tuna) at a minimum of minus four degrees Fahrenheit for seven days or minus 31 degrees for fifteen hours. Tuna receives an exception to this rule because it is rarely infected by parasites, although most restaurants treat it to the same freezing times to maintain its freshness.

You are more likely to be infected by a parasite eating cod, herring, mackerel, or squid at your own home, local restaurant, or when traveling outside the U.S., where freezing fish to parasite-killing temperatures is not required by law.

Parasite Risk: Extremely Low


Tuna, a common sushi ingredient, is notorious for its high levels of mercury. Pregnant women and children are warned to avoid sushi and other forms of high-mercury fish due to the increased danger levels of exposure. Mercury is a neurotoxin that can affect a growing brain and nervous system, and impact speech, hearing, coordination, memory, and cognitive thinking. A recent study found that tuna sashimi contains the highest levels of methylmercury out of all the fish-sushi. According to the Natural Resources Defense Council Guide to Mercury Contamination in Fish, salmon or flounder have the least amount of mercury, and snapper may have a moderate amount of mercury.

Mercury Risk: Depends on fish. High (tuna), Moderate (snapper), and Low (salmon)


Many foods are at risk of bacterial contamination, not just raw fish. Salmonella is a bacteria that can contaminate all sorts of foods, including sushi. Vibrio parahaemolyticus is a bacteria that is associated with raw or undercooked fish and shellfish, including oysters.

Sushi rice can be contaminated by the bacillus cereus bacteria when it sits at room temperature. Sushi rice prepared with a traditional vinegar solution is usually safe from bacterial contamination, since the acid lowers the pH to a microbe-killing 4.1. Beware of sushi rolls that have been sitting out unchilled, however, and don’t eat any sushi that has been refrigerated for longer than 24 hours, just to be safe. Eating sushi may come with a moderate risk of bacterial contamination, but no more so than any other food that you consume.

Bacteria Risk: Moderate


Chemicals dumped into our oceans have found their way into our fish populations. Pesticides have been found in the waters and in the fish surrounding us. The EPA named the Palos Verdes Peninsula in California “the most hazardous dumping grounds in the nation.” Pesticides have been detected in the oceans as well as the river systems that Pacific salmon call home. Roundup, one of the more commonly found pesticides found in fish, has also shown to increase the incidence of other diseases in fish.

Pesticide Risk: Moderate

Radioactive Cesium

The Fukushima nuclear disaster in Japan has sent radioactive contamination drifting across the Pacific ocean to the California coast. Researchers from Stanford University reported in 2012 that 15 Pacific bluefin tuna had migrated from Japan to California with radioactive cesium levels 10 times higher than before the disaster, and Oregon State University researchers have found tuna on the Oregon coast with triple the levels found before. Despite the increased levels of radiation found in seafood, the levels are still considered too low to be a health risk and the fish to be safe for human consumption.

Radiation Risk: Low

Bottom line: Sushi can pose low risks if you eat it at a reputable restaurant that adheres to rules on freezing fish, properly prepares sushi rice with vinegar, and if you choose low mercury fish such as salmon over higher mercury tuna. All foods will carry some risk of bacterial contamination, and radiation exposure is still considered to be a low risk for any seafood.

Melissa Zimmerman

Melissa Zimmerman is a freelance writer specializing in health and nutrition writing. A California native living in Central Oregon, Melissa enjoys the outdoor adventures and beauty of the Pacific Northwest. When she is not kayaking on the river, you can find her in a yoga studio or practicing asanas outdoors. Melissa is a big believer in the power of yoga and healthy food to radically improve anyone's quality of life.

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