Fish is a wonderful source of protein and heart-healthy omega-3 fatty acids. But…
The world’s oceans contain high levels of mercury and other contaminants, making fish our primary source of environmental exposure to mercury poisoning.
Nearly all fish contain trace amounts of mercury, some more than others. They absorb it from water as it passes over their gills and as they feed on other marine organisms. Larger predatory fish get a higher dose from their prey.
Mercury binds tightly to proteins in fish tissue, including muscle. The toxic mineral builds up in a process called bioaccumulation, and cooking does not appreciably reduce the mercury content.
Researchers still don’t know the precise impact of toxicity on individual human health, and some say mercury levels in fish may not be as toxic as many people think. It’s also important to know that fish contain high levels of selenium, a mineral that specifically binds and neutralizes mercury. Most fish, in fact, contain more selenium than mercury, and some researchers believe that this balance offsets the presence of mercury eliminating the risk of mercury poisoning from eating fish.
For now, and until all this mercury poisoning uncertainty gets sorted out, I prefer to err on the side of caution. I love eating fish but I choose my fish very carefully. And you should, too.
Eating Fish Safely
If you enjoy eating fish, I suggest visiting the web site gotmercury.org. There you’ll find an online calculator that enables you to select different types of fish and, with a few keystrokes, find out the mercury levels you may be getting with a serving of fish. These calculations of mercury levels in fish are based on government data.
Depending on the fish involved and your weight, the calculator gives you a percentage of the EPA limit for the amount of mercury levels in fish that a person can be exposed to on a daily basis over a lifetime without mercury poisoning.
The calculator can’t tell you, of course, how the risks of mercury levels in fish may translate into specific ills. However, it’s a handy tool for raising your awareness of mercury levels when eating fish.
Here are some general mercury poisoning guidelines for eating fish:
- Pregnant women avoid fish altogether to prevent possible harm to a sensitive fetus.
- Avoid all freshwater and farm-raised fish. Mercury levels in freshwater fish vary. In general, bass, pike, muskellunge, and walleye have higher mercury levels.
- Beware of fresh and frozen tuna—the mercury content ranges from 0.5 ppm to 1.5 ppm. Canned tuna consists of smaller species with lower mercury levels.
- Be sure your daily supplement program includes selenium (200–300 mcg) and magnesium (400–800 mg). Both protect your body from mercury. Many people are deficient in these important minerals.
Now It's Your Turn: Do you follow these mercury in fish guidelines before you eat?