The Deadly Mercury In Our Fish

| October 10 , 2017 , 15:52 IST

Pregnant women are told to abstain from high mercury fish - mackerel, shark, swordfish, tuna - as it inhibits the development of the nervous system of an unborn child.

Mercury is a pollutant that can be toxic to the human nervous systems. When mercury is released into the atmosphere, it easily dissolves in fresh water and seawater. Fish and other aquatic animals ingest the mercury, and it is then passed along the food chain until it reaches humans. A type of mercury called methylmercury is most easily accumulated in the body and is particularly dangerous. About 80 to 90 percent of organic mercury in a human body comes from eating fish and shellfish, according to a paper published by the Journal of Preventative Medicine and Public Health.

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But what about the rest of us? Can we consume high mercury fish?


Popular food fads and umpteen dos and donts related to food can leave us confused. For most foods, we can find a solid case reasoning why it is great for you as much as why it can be harmful. Fish is one such favourite subject for food enthusiasts who love to both canonize it or demonize it. Of course a diet of fish is a good source of high quality protein while being low in saturated fat. It is also an excellent source of Vitamin D and Omega-3. The fat-soluble vitamin D is a nutrient that most people are deficient in. Omega-3 are fatty acids crucial for our body and brain to function optimally. Yet the effect of regular, low doses of methylmercury that is contained in some fish more than in others, andthat causes a wide range of conditions including neurological and chromosomal problems, is less understood.

Here are a few reasons why we are not wary of mercury poisoning in our fish:

First, there are stark and rather ironic contradictions between the benefit of fish versus the adverse effect of mercury contained in it. For example, on one hand Omega-3 helps in brain development whereas on the other hand mercury hinders it. Another example is that heart diseases increases with mercury exposure, while fish oils may reduce the risk of cardiac death.

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Second, defining the amount of fish we should eat to avoid harm is complicated because methylmercury affects each one of us differently depending on our weight, age and genetics.

Third, fresh fish bought from the market do not carry a nutrition content label. There is therefore little way to find out the mercury levels of the fish we eat!

And so, a fair verdict on fish is this: Pregnant or not the best solution is to completely abstain from high mercury fish. Instead eat fish that are low in the food chain such as salmon, sardines, trout, regularly, but each time in limited quantities amounting to say 350 grams a week. This is the best way to enjoy the benefits of fish, while keeping your body low on toxic mercury.