The Bottom Line of Eating Fish
For years, doctors and dietitians have been recommending that we eat fish to help prevent coronary heart disease. Recent reports about high levels of mercury, polychlorinated biphenyls and other toxins in some of the most popular types of fish have caused many health-conscious individuals to rethink their diets.
To clear up the confusion, we spoke with Eric Rimm, ScD, a leading expert on the nutritional value of fish.
- Is fish still a healthy food choice? Absolutely, research going back to the 1970’s has established the omega-3 fatty acids from fish are a major weapon against heart disease and sudden heart attacks.
- The anti-inflammatory effects of omega-3 are so powerful that scientists are researching their effect on a host of other diseases, including type 2 diabetes, rheumatoid arthritis and prostate cancer. There is also some evidence that omega-3 can improve cognitive function and so may help protect against Alzheimer’s disease. If we stopped eating fish, all these benefits would be lost.
- What about the mercury and other contaminants found in fish? All fish contain some pollution- related mercury. Larger predatory fish have higher mercury levels because they take in and store the mercury found in the smaller fish they eat. Smaller fish have the least amount of mercury.
- Because mercury may affect the neurological development of children, the FDA recommends that women who are pregnant or who might become pregnant should avoid eating the fish with the highest mercury levels, specifically shark, swordfish, king mackerel and tilefish. In addition, this group should eat no more than 12 ounces per week of fish that contains lower mercury levels, such as shrimp, canned light tuna, Pollack, and catfish.
- Women who are not likely to become pregnant and all adult men can choose to follow the same recommendations if they want to be as safe as possible.
- Should we be concerned about the levels of PCB’s that are now reportedly in fish? PCB’s and other toxins do pose some health threats and may even contribute to cancer development, particularly such hormone-related cancers as breast cancer. But I’d like to put the risk into perspective.
- First, the data, based mainly on animal studies, are limited regarding actual dangers of these toxins in fish. We don’t know if the level of PCB’s found in fish are actually dangerous to humans. However, several studies have shown that people who eat fish at least once a week have a lower risk of sudden death from heart disease and a lower risk of overall mortality.
- Second, it comes as no surprise to most people to learn that we eat PCB’s all the time. Of all the PCB’s in our diet, one-third come from milk and cheese…..one-third come from chicken, beef, and pork….and one-third come from fish. Almost all food products contain PCB’s, even those labeled organic. Typically, organic foods contain PCB levels that are between 1/10th and 1/1000th of conventionally grown foods.
- If you stop eating fish and start eating steak, for example, you’ll be getting approximately the same amount of PCB’s, but you will be missing out on the healthy omega-3 fatty acids.
- Could we avoid the toxins altogether by taking fish oil pills or flaxseed supplements? Not necessarily. The research is still ongoing, but there is some evidence that fish oil capsules contain, per gram of oil, the same levels of PCB’s as the fish they come from. They also may contain very small amounts of mercury. Although eating fish is more beneficial, fish oil supplements are an option if you don’t like the taste of fish.
- Flaxseed oil also contains omega-3 fatty acids, but in a different form of omega-3 which does not act identically to those found in fish and may not be as beneficial.
- How should people eat fish to get the most benefits with the least harm? Vary the types of fish you eat. Limit your intake of shark, swordfish, king mackerel, and tilefish to once a month to reduce your exposure to high levels of mercury.
- Aim to eat fish rich in omega-3 fatty acids at least once a week. These include salmon, trout, tuna, shellfish, sardines, herring and mackerel.
- If you eat canned tuna, choose chunk light over albacore or solid white. Flaky white fish such as cod are not high in omega-3 and so offer very little benefit.