De-Bunking the Fish Myth

Posted by Claire | Sunday July 8, 2007

"Salmon is an excellent source of omega-3 fatty acids which helps protect you from heart disease."

"Limit your intake of seafood, farmed or otherwise, because of dangerous contamination."

Which statement is true? It's no wonder consumers are confused about what to eat, since the guidelines seem to change all the time. On one hand, environmental groups question food safety, and at the other end farmers and producers claim that problems are exaggerated and reports prejudicial. Government warnings seem to waffle between the two.

In fact, both statements are true. Salmon and other fatty fish are the best natural source of omega-3s, while also being low in saturated fats. Risks associated with heart disease, rheumatoid arthritis, and depression are positively impacted by a diet including omega-3 fatty acids.

Concerns about contamination need to be better understood. Our oceans are polluted with many chemicals that all sea creatures absorb. Certain compounds are stored in fat and can persist for many years. Ocean food chains are generally much more complex than land-based food chains, and the contaminated fats are passed up the chain to the highest level (this is called biomagnification). Top-end consumers, such as large fish, polar bears, and humans consume the accumulated contamination over the entire food chain and in turn store it in their own fats. These fats can generally be purged through fat loss (by weight loss or otherwise), but during weight loss the chemicals are released into the blood stream and can sicken the host until they are flushed out.

The top contaminants of concern are mercury, PCBs, and dioxins. Mercury exposure can cause a variety of mental and pscychological health problems, PCBs are endocrine disruptors, and dioxins are known to cause cancer. To some extent, these are found in many environments, not just seafood. Occupational exposure, drinking water, and contaminated air can be sources of some of these. Eliminating seafood from your diet entirely will not protect you from these chemicals, and will mean you miss out on other health benefits (such as omega-3 fats) that this food source offers.

The US FDA and Health Canada set a tolerance limit for PCBs in fish at 2 ppm (parts per million), and generally both farmed and wild seafood do not exceed this value. However, environmental groups claim this does not go far enough to protect consumers. Those in the seafood industry say their livelihood is being threatened by inflammatory publicity of this issue, since fish is only one source of many for the contaminants in question.

Experts agree on a few basic facts. First, you should eat a variety of fish and always in moderation. Certain fish such as king mackerel, shark and swordfish should not be eaten at all (these are at the top of their respective food chains and therefore have the maximum contamination). The American Heart Association recommends two 6-ounce servings of fish per week to obtain a helpful amount of omega-3s. Pregnant and nursing women and children

should limit their intake even more (these chemicals can cross the placenta and be excreted in breast milk fats, and children's small size make them more susceptible than adults) and avoid certain foods altogether.

The reason for concern about farmed fish is that their feed may be derived from food sources they would not consume in the wild, and may include higher trophic-level organisms. Many analyses have concluded that the levels of contamination are indeed higher than in wild fish, though not necessarily exceeding government-set tolerances (editorial comment: "for what it's worth".)

Do your homework. Find an industry opinion here, an environmental scientist perspective here, and Health Canada's statement here.

Mamaluv is a ChickAdvisor writer, Mother of 3 and seafood addict. She also happens to have a background in environmental science.

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