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Think Twice About Ordering Sushi: You Could be Poisoned With Mercury

Harold Mandel's picture
Japanese sushi with raw fish

Sushi tastes great, but it may not be great for your health. A lot of people, aside from the Japanese themselves, have enjoyed the fine taste of Japanese sushi. Along with some sake and Kirin beer this makes for a really delicious meal. However, there have been concerns about the possibility of picking up intestinal parasites from sushi. Another area of concern has been the possibility of possible toxic metal poisoning from contaminated fish which is used for sushi.

There have not been many papers published dealing with eating sushi and its role in methylmercury exposure, according to an article in the Journal of Risk Research. For the research reviewed here scientists interviewed 1289 people in a New Jersey university community regarding their fish and sushi consumption. The researchers also collected samples of sushi for mercury analysis from New Jersey stores and supermarkets and from New York City, and Chicago.

It was observed that total mercury levels varied significantly by the type and quality of sushi. Tuna sashimi had the highest mean levels of mercury. The large bluefin tuna, which are considered a delicious source of sushi, have the highest mercury levels and happen to also be the most endangered from overfishing. The data for this research have suggested that sushi may pose a significant risk from mercury exposure. EmaxHealth reporter Tim Boyer, PhD has written about which sushi contains the least mercury.

Tuna sashimi contains the highest levels of methylmercury

In a review of this research published by Taylor and Francis via Alpha Galileo it has been written that eating sushi can increase your risk of cardiovascular disease. As noted, this study has showed that tuna sashimi contains the highest levels of methylmercury in fish-sushi. Methylmercury exposure in humans as a result of excessive fish consumption has been associated with:

1: Neurodevelopmental deficits

2: Poorer cognitive performance

3: Increased rates of cardiovascular disease

It was also discovered that higher levels of methylmercury can undermine the positive effects of omega-3 fatty acids. Omega-3 fatty acids generally have many health benefits, which include:

1: Reducing cholesterol levels

2: Reducing the risk of some cancers

3: Reduced incidence of heart disease

4: Reduced incidence of high blood pressure

5: Reduced incidence of stroke

6: Reduced incidence of pre-term delivery

About 92 percent of participants in the study ate an average of 5 fish and fish-sushi meals per month. The top 10 percent of all of the participants from across all ethnic groups were found to exceed the generally accepted minimal risk levels for intake of methylmercury. Consistently, large tuna, such as the Atlantic bluefin or bigeye, which are really liked for sushi, were found to contain the highest mercury levels. Sushi which was made with eel, crab, salmon and kelp were observed to have lower levels of methymercury.

It has been written by Live Science that sushi lovers do not need to worry about the raw fish they consume, as long as the sushi has been prepared properly, in accordance with regulations by the Food and Drug Administration. Sushi preparers must take extra precautions with both the raw fish and the rice.

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However, raw fish actually has many potential hazards for consumers. In fish that is not fresh bacteria can develop and produce enzymes which are called histamines that may result in Scombroid poisoning. Furthermore, many tropical-water fish may also have a natural toxin which is called ciguatera. This toxin which causes gastrointestinal and neurological symptoms.

Precautions can be taken to kill parasites in fish

Sushi restaurants generally take special precautions in handling and preparing their fish. One required step involves freezing fish at temperatures of -4 degrees Fahrenheit (-20 degrees Celsius) for at least seven days, or freezing at -31 degrees Fahrenheit (-35 degrees Celsius) for 15 hours, which kills any parasites. The freezing is done on raw fish to kill parasites. And so raw fish in sushi is generally free of parasites. However, the bacteria bacillus cereus can spread rapidly in rice that sits at room temperature. An acidic bath in a vinegary solution that lowers the PH to 4.1 generally kills troublemaking microbes in sushi rice.

Exposure to methylmercury has become another serious concern for sushi eaters. People in the U.S. are primarily exposed to methylmercury when they consume fish and shellfish that contain methylmercury, according to the United States Environmental Protection Agency. A lot of people have at least trace amounts of methylmercury in their tissues, which reflects methylmercury’s widespread presence in the environment and the exposure of people through the consumption of fish and shellfish.

There are various factors which determine how severe the health effects are from mercury exposure, which include:

1: The chemical form of mercury

2: The dose

3: The age of the person exposed, with the fetus being the most susceptible

4: The duration of exposure

5: The route of exposure, such as inhalation, ingestion, dermal contact, etc.

6: The health of the person exposed

In fetuses, infants, and children, the primary health effect from excess methylmercury exposure is impaired neurological development. In fact exposure to methylmercury in the womb, which can result from a mother's consumption of fish and shellfish which contains methylmercury, can negatively affect a baby's growing brain and nervous system. Children exposed to methylmercury in the womb may experience problems with cognitive thinking, memory, attention, language, and fine motor and visual spatial skills. Emaxhealth reporter Robin Wulffson, MD has reported on mercury exposure during pregnancy and ADHD risk in offspring.

According to human biological monitoring by the Centers for Disease Control and Prevention from 1999 and 2000, most people have blood mercury levels which are below a level which is associated with possible health effects. However, outbreaks of methylmercury poisonings have made it very clear that adults, kids, and developing fetuses are at risk from ingestion exposure to methylmercury. Special precaution should be taken when dealing with fetuses because their developing nervous system may be more vulnerable to methylmercury than the adult nervous system is.

Other symptoms of methylmercury poisoning may include:

1: Impairment of the peripheral vision

2: Disturbances in sensations, such as "pins and needles" feelings in the hands, feet, and around the mouth

3: Lack of coordination of movements

4: Impairment of speech, hearing, walking; and muscle weakness.

I have observed that sushi is indeed a very popular dish. There appears to be a trend towards eating more cooked sushi and less raw sushi due to concerns about possible exposure to parasites. However, cooking sushi, or freezing it to very low levels prior to preparation, to kill parasites, does not clear contaminated fish of methylmercury. Methylmercury poisoning can cause very serious health problems, and so there should be aggressive initiatives to educate the public about this possibility from eating sushi. Also, environmental initiatives aimed at cleaning up our seas, as we search for manners to lower methylmercury content in tuna and other fish, are essential.