Mercury in Fish and SeaFood
Seafood Contains Protein and Essential Fatty Acids But Also Mercury.
Seafood is a great source of protein and essential fatty acids, but some species are not healthy to eat.
The Controversy
Some environmental groups are publishing frightening information that would make people want to avoid fish altogether. The fishing industry is retaliating with information that says there’s no problem. The truth is somewhere in between.
The controversy concerns the levels of mercury in fish, because mercury is a very toxic substance that causes terrible birth defects. The controversy over the amount of seafood people should eat is more important to women because of pregnancy.
While there is mercury in all seafood, some species, in some locations, contain too much mercury for people to eat – but especially for pregnant women or women who may become pregnant.
Is this just a theoretical problem created by watchdog groups?
The US Center for Disease Control (CDC) issued a report of a study of 3,600 individuals. It 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.
Dr. Jane Hightower, a San Francisco physician, released a report of 89 people who were tested over the course of a year to track their blood levels. Of these, 79 had high levels of mercury – some were 15 times higher than the maximum safe level. This unusual result shows that some geographic areas have very high levels of mercury pollution.
Is the “safe” dose really safe?
This is a troubling question. 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).
Should people avoid fish or not?
Another troubling question. Some people have alternative sources of protein and essential fatty acids so they don’t have to eat fish. But 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. Most places in the world have excellent sources of protein other than fish. Those populations can eat less fish without damaging their health from a lack of protein.
The benefits of eating healthy fish:
- excellent source of proteins
- excellent source of essential fatty acids
- healthy pregnancies and babies from eating low-mercury fish
The dangers of fish with too much mercury:
- neurological damage to adults, children and unborn babies
- mental retardation in unborn babies and children
- increased risk of heart attacks in adults
What to do?
Eat fish intelligently. Choose the type of fish according to the average level of mercury. See the FDA website for estimated mercury levels of many species.
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.
Seafood species 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.
Seafood species to avoid
Seafood species that are known to be especially high in mercury include the larger species that 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.
Summary
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.
Resources:
- Hightower, J & Moore, D. (April, 2003). Mercury levels in high-end consumers of fish. Environmental Health Perspectives.
- Rissanen T, Voutilainen S, Nyyssonen K, Lakka TA, Salonen JT. (2000). Fish oil-derived fatty acids, docosahexaenoic acid and docosapentaenoic acid, and the risk of acute coronary events. Circulation 102:2677-2679.
- Salonen JT, Seppanen K, Nyyssonen K, Korpela H, Kauhanen J, Kantola M, et al. (1995). Intake of mercury from fish, lipid peroxidation, and the risk of myocardial infarction and coronary, cardiovascular, and any death in eastern Finnish men. Circulation 91(3):645-655.
- Center for Disease Control. (November 5, 2004). Blood Mercury Levels in Young Children and Childbearing-Aged Women --- United States, 1999—2002, CDC Report, 53(43);1018-1020
