- Jun 25, 2006
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by Monica Mollica
Fish oil is a popular supplement, and for good reasons (I will soon post a long article about all the beneficial health effects of fish oil)! But what about fish? After all, fish is a good protein source…Yes, fish is an excellent source of both protein and the omega-3 fatty acids EPA and DHA (in case of fatty fish like salmon and mackerel).
Unfortunately, concerns have been raised against high fish consumption for several reasons. First, fish is a relatively expensive food with restricted availability in certain areas. Second, fish also has a characteristic taste that many people do not like. And last but not least, fish (especially fatty fish that is a good source of EPA and DHA) contains a high level of environmental toxins, among all mercury (also called methylmercury) and PCBs (polychlorinated biphenyls) 1-6. It is the contaminants in fish that have raised the most concerns.
Fish absorb environmental toxins as they grow, and so it builds up in them. It builds up more in some types of fish and shellfish than others, depending on what the fish eat and in which waters they live, which is why the levels vary 2, 7-9. So while the omega-3 fats EPA and DHA in fish protect against cardiovascular disease, contaminants in fish (especially mercury) increase the risk for cardiovascular disease and mortality 6, 10-13. While some believe the benefits of consuming fish outweigh the dangers 14, other scientists counter that the fish contamination issue warrants a serious considerations and warn against increasing fish consumption 3, 4, 15, 16. This warning is substantiated by the finding that high-fish consumers often have blood mercury levels exceeding the maximum level recommended by the U.S. Environmental Protection Agency and National Academy of Sciences 17.
High levels of environmental toxins not only increase the risk for cardiovascular disease, but also cause neurologic damage to developing fetuses and young children 1, 2. In response to these concerns, the Food and Drug Administration and the Environmental Protection Agency issued a joint advisory in 2004 for women who are pregnant or might become pregnant, nursing mothers, and young children 2:
1.) Do not eat shark, swordfish, king mackerel, or tilefish because they contain high levels of mercury.
2.) Eat up to 340 g (12 oz)/wk (2 average meals) of a variety of fish and shellfish that are lower in mercury, such as shrimp, canned light tuna, salmon, pollock, and catfish. Furthermore, albacore (white) tuna has more mercury than canned light tuna. So, when choosing your 2 weekly meals of fish and shellfish, you may eat up to 170 g (6oz)/wk (1 average meal) of albacore tuna.
3.) Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 170 g (6 oz)/wk (one average meal) of fish you catch from local waters, but do not consume any other fish during that week.
A high intake of mercury can also cause endocrine disruptions; among all it has been shown that high mercury levels in the body decreases levels of thyroid hormones and testosterone 18, 19. Since thyroid hormones increases energy expenditure 20-22, while testosterone increases muscle mass 23, this is especially negative for people who are trying to built muscle and/or loose excess body fat to get in shape.
Because of the varying amounts of mercury and PCBs in fish, consumption of a variety of fish species, both wild and farmed, is recommended to minimize exposure to environmental toxins while maximizing health benefits. However, while it is safe for most people to consume 2-3 servings of fish per week 10, 24, 25, this amount is not enough to provide the health promoting and fat loss effects of EPA and DHA.
Fish oil is a popular supplement, and for good reasons (I will soon post a long article about all the beneficial health effects of fish oil)! But what about fish? After all, fish is a good protein source…Yes, fish is an excellent source of both protein and the omega-3 fatty acids EPA and DHA (in case of fatty fish like salmon and mackerel).
Unfortunately, concerns have been raised against high fish consumption for several reasons. First, fish is a relatively expensive food with restricted availability in certain areas. Second, fish also has a characteristic taste that many people do not like. And last but not least, fish (especially fatty fish that is a good source of EPA and DHA) contains a high level of environmental toxins, among all mercury (also called methylmercury) and PCBs (polychlorinated biphenyls) 1-6. It is the contaminants in fish that have raised the most concerns.
Fish absorb environmental toxins as they grow, and so it builds up in them. It builds up more in some types of fish and shellfish than others, depending on what the fish eat and in which waters they live, which is why the levels vary 2, 7-9. So while the omega-3 fats EPA and DHA in fish protect against cardiovascular disease, contaminants in fish (especially mercury) increase the risk for cardiovascular disease and mortality 6, 10-13. While some believe the benefits of consuming fish outweigh the dangers 14, other scientists counter that the fish contamination issue warrants a serious considerations and warn against increasing fish consumption 3, 4, 15, 16. This warning is substantiated by the finding that high-fish consumers often have blood mercury levels exceeding the maximum level recommended by the U.S. Environmental Protection Agency and National Academy of Sciences 17.
High levels of environmental toxins not only increase the risk for cardiovascular disease, but also cause neurologic damage to developing fetuses and young children 1, 2. In response to these concerns, the Food and Drug Administration and the Environmental Protection Agency issued a joint advisory in 2004 for women who are pregnant or might become pregnant, nursing mothers, and young children 2:
1.) Do not eat shark, swordfish, king mackerel, or tilefish because they contain high levels of mercury.
2.) Eat up to 340 g (12 oz)/wk (2 average meals) of a variety of fish and shellfish that are lower in mercury, such as shrimp, canned light tuna, salmon, pollock, and catfish. Furthermore, albacore (white) tuna has more mercury than canned light tuna. So, when choosing your 2 weekly meals of fish and shellfish, you may eat up to 170 g (6oz)/wk (1 average meal) of albacore tuna.
3.) Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 170 g (6 oz)/wk (one average meal) of fish you catch from local waters, but do not consume any other fish during that week.
A high intake of mercury can also cause endocrine disruptions; among all it has been shown that high mercury levels in the body decreases levels of thyroid hormones and testosterone 18, 19. Since thyroid hormones increases energy expenditure 20-22, while testosterone increases muscle mass 23, this is especially negative for people who are trying to built muscle and/or loose excess body fat to get in shape.
Because of the varying amounts of mercury and PCBs in fish, consumption of a variety of fish species, both wild and farmed, is recommended to minimize exposure to environmental toxins while maximizing health benefits. However, while it is safe for most people to consume 2-3 servings of fish per week 10, 24, 25, this amount is not enough to provide the health promoting and fat loss effects of EPA and DHA.