Fish, Mercury and Essential Fatty Acids

The Controversy

There’s a controversy over the amount of fish people should eat. The question is more important to women because of pregnancy.  The controversy concerns the levels of mercury in fish because mercury is a very toxic substance that causes terrible birth defects. Some environmental groups are publishing frightening information that would make women want to avoid fish altogether.  The fishing industry is retaliating with information that would lead women to think there’s no problem.  The truth is somewhere in between.

There is mercury in all fish.  In some fish, in some locations, there is way too much mercury for women or men to eat—but especially for pregnant women or women who may become pregnant.

Is this just a theoretical problem created by watch-dog groups?

No. A report published by the Center for Disease Control (CDC) of 3600 individuals showed that 2% of Hispanic people, 6% of whites and 5% of African Americans had levels of mercury in their blood that was above the level that is assumed to be safe by the Environmental Protection Agency (EPA). That’s about 15 million people in the USA with too much mercury in their blood.

In another report by Dr. Jane Hightower, a San Francisco physician, 89 people were tested over the course of a year to track their blood levels. 79 of the 89 people had high levels of mercury—some were 15 times higher than the maximum safe level. This unusual result shows that some geographic areas have some very high levels of mercury pollution.

Another troubling issue is that the “safe” dose set by the EPA is only based on neurological damage.  Newer studies have shown an association with increased heart attacks and death from mercury levels close to the current “safe” dose (RfD) set by the EPA (Rissanen et al. 2000; Salonen et al. 1995, 2000).

So, if that’s true, should women avoid fish or not?

The answer depends on whether a woman has alternative sources of protein and essential fatty acids in her diet.  For most of the people on the planet, fish is the best source of essential fatty acids and an excellent source of protein.

For the people who live in industrialized countries, there are alternative sources of essential fatty acid–supplements that provide the benefits of the fats without the risk of mercury.

In most places in the world there are excellent sources of protein other than fish.

The benefits of fish: If a woman avoids seafood, she’ll lose out on the great benefits of eating fish.  They are excellent sources of proteins and essential fatty acids.  Pregnant women should get plenty of both for their own health and the health of the unborn child.

The dangers of fish: If a pregnant woman eats enough of the wrong kinds of fish, her child will probably have a reduced IQ, may even be mentally retarded or have other developmental problems.  Mercury is very, very toxic.

What to do?

What makes sense is to eat fish intelligently.  Choose the type of fish according to the likelihood that it has a small amount of mercury. See the FDA website for estimate mercury levels of many species.

Frequently recommended as being low in mercury are: mid-Atlantic blue crab, croaker, flounder in summer, haddock, farm-raised trout, wild Pacific salmon and shrimp.  Try to learn where the fish were caught and what the mercury levels are in that area.  There are data on mercury pollution by state available at the Environmental Working Group website.

Fish that are a little higher in mercury but safe to eat once per month are: mahi mahi, blue mussel, Eastern oyster, cod, pollock, Great Lakes salmon, Gulf Coast blue crab, wild channel catfish, and lake whitefish.

It also makes sense to use an essential fatty acid supplement to get the benefits with less risk of mercury contamination.

To increase their chances of healthy babies, women who are pregnant or may become pregnant should have their blood mercury level checked periodically.

What to avoid

Fish that are known to be especially high in mercury are the larger species who are in the water longer and therefore absorb more mercury into their tissues: shark; swordfish; king mackerel; tilefish; larger tuna species like albacore, big-eye or yellow-fin; sea bass; Gulf Coast oysters; marlin; halibut; pike; walleye; white croaker and largemouth bass.


Find the best sources of protein and essential fatty acids in your area. Include fish that are known to be safe since they are a good source of both. Have your blood mercury levels checked occasionally—especially if you’re pregnant or may become pregnant.

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