Fish is a wonderful source of protein and heart-healthy omega-3 fatty acids. But…
The world’s oceans contain enormous quantities of mercury and other contaminants, making fish our primary source of environmental exposure to mercury.
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 the levels 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.
For now, and until all this uncertainty gets sorted out, I prefer to err on the side of caution. I choose my fish very carefully. And you should, too.
Play It Safe
If you enjoy eating fish, I suggest visiting the web site www.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 how much mercury you may be getting with a serving of fish. These calculations 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 a person can be exposed to on a daily basis over a lifetime without appreciable risk of side effects.
The calculator can’t tell you, of course, how those risks may translate into specific ills. However, it’s a handy tool for raising your mercury awareness.
Here are some general guidelines for playing it safe with 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 are higher in mercury.
- 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.