By now you’ve probably heard about the health benefits of omega-3s, those “good-for-you” fats that reduce inflammation and may lower the risk of heart attack, stroke and, possibly, other age-related diseases such as Alzheimer’s disease.
The best source of omega-3 fats is fatty fish like salmon, mackerel, herring, halibut and tuna, but there’s also concern about the mercury content of these fish. This raises the question – do the benefits of omega-3s from fish outweigh the risks of mercury exposure?
Why Fish Are a Source of Mercury
How are fish exposed to mercury? Mercury is found naturally in the environment where it’s produced by the breakdown of rocks and from volcanic activity, but most of the mercury we’re exposed to is released into the air from coal-burning plants. From there, mercury ends up in waterways where it becomes methylmercury. It then enters the bodies of fish living in the water.
Larger fish that are higher in the food chain have higher methylmercury levels than fish that are smaller in size and are lower in the food chain. So a large fish that’s older will have had more time to accumulate mercury. Most fish, even smaller ones, contain some mercury, although some have only very tiny amounts.
Is It Safe to Eat Fish That May Have Been Exposed to Mercury?
According to an analysis published in the Journal of the American Medical Association, the benefits of eating fish outweigh the risks when you choose your fish wisely. When researchers looked at blood levels of omega-3s in men who had experienced a heart attack, they found that even a small increase in omega-3s reduced their heart attack risk significantly.
Of course, this study was carried out on a sub-group of people, men who had already had a heart attack. For people at low risk for heart disease, it’s not as clear cut. Still, according to preliminary research, omega-3s are a good source of healthy fats that reduce inflammation and blood pressure and have the potential to prevent other health problems that occur with aging. One study even showed that omega-3s slow down cellular aging.
Get the Benefits of Omega-3s without the Risks
Some people hope to get their omega-3s from eating plant-based sources like flaxseed, sesame seeds and chia, but these foods contain alpha-linolenic-acid, a form of omega-3 that needs to be converted to EPA and DHA, more powerful omega-3s, to get the full benefits. This conversion is not efficient in everyone and studies have shown conversion rates as low as 0.1%. The conversion rate for most people seems to be between 5% and 20%.
Women have a greater ability to convert alpha-linolenic acid to EPA and DHA than men. Still, if you’re a low converter, you may not necessarily get the heart-healthy, inflammation-lowering benefits of omega-3s from plant-based sources that contain only alpha-linolenic-acid.
The best option? Choose fatty fish that are smaller and lower in the food chain and avoid large fish such as king mackerel, shark, swordfish, tilefish and other big fish higher in the food chain. You can find lists of fish that typically contain higher levels of mercury online.
Better choices are wild-caught salmon, shrimp, sardines, catfish, pollock and light tuna from a can. Avoid albacore tuna since it’s higher in mercury than regular canned tuna. The other way to lower the risk is to eat fatty fish only twice a week. Two meals a week is enough to get the benefits without the mercury exposure.
What about Fish Oil Supplements?
This is a good option for people who don’t like the taste of fish. Fish oil supplements that have been purified by a process called molecular distillation are the best choice because this process removes most of the mercury.
Always buy fish oil supplements from a reputable source and verify that they use molecular distillation to purify their product. The advantage of taking a purified fish oil supplement is that the purification process removes other impurities like PCBs and dioxins – but talk to your doctor before taking a fish oil supplement. They can interfere with some medications.
The Bottom Line?
Considering the high rate of heart disease in this country and the fact that so many people eat an inflammatory diet, the benefits of eating fish likely outweigh the risks of mercury exposure. Mercury exposure is more of a risk in young children and pregnant women than it is in healthy adults since mercury affects nervous system development.
At the same time, if you’re pregnant you need more omega-3s in your iet for the health of your unborn baby. Omega-3s are important for brain development. Talk to your doctor about this, and choose your fish wisely to get the benefits with minimal risk or consider taking a purified fish oil supplement instead.
Also, keep abreast of the latest research on omega-3s. Some recent studies question whether omega-3s, especially in supplement form, actually lower the risk of heart disease. One study also showed a link between omega-3s and a higher risk for prostate cancer in men. That’s why it’s best to get omega-3s from dietary sources like fish than to take a supplement if at all possible.
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Harvard School of Public Health. “Fish: Friend or Foe?”
American Cancer Society. “Omega-3 Fatty Acids Linked to Increase in Prostate Cancer Risk”