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Omega-3s, Fish, and Mercury in the Diet

How to Include Fish in Your Diet Without Worry


Updated January 24, 2011

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

So, one day you decide to eat more fish because you have heard that they are heart healthy. Then the very next day you see a television news report that eating fish can be dangerous because it can contain mercury. What is a health-conscious consumer to do? Do you eat fish or avoid it? Eat some fish, but not others? Is an omega-3 supplement healthy? Are there varied recommendations for different people? Read on for the low-down on fish for heart health and how to avoid mercury risk.

Fish For Heart Health Oily or "fatty" fish such as salmon, tuna, mackerel, and sardines are an excellent source of the heart healthy omega-3 fatty acids (omega 3s, for short). Nutrition research studies have shown that omega-3s may reduce inflammation, slow plaque collection in the arteries, and reduce the risk of cardiac events in individuals who already have heart disease.

Is an Omega-3 Supplement as Good as Fish? Omega-3s are a unique form of nutrient known as "essential," meaning that you must obtain them from food or a supplement pill. Your body can not make the nutrient from other fats, carbohydrates, or proteins. Omega-3s are not very common in the foods we eat, and are mostly found in fish and seafood.

If you don't enjoy fish, you can opt for a supplement. Current research indicates that they are as heart healthy as food sources.

More: Fish versus Fish Oil Supplements

How Much Omega-3 Do I Need?

If you are taking an omega-3 fish oil supplement and do not eat fish or seafood regularly, 500 mg per day is a reasonable minimum dosage, but be sure to check with your doctor to learn the appropriate dosage for you.

If you do not want to take an omega-3 supplement and do eat fish or seafood, consider having at least one omega-3 rich food source per day. You can vary between non-fish and fish sources. For example a handful of walnuts, a tablespoon of canola oil over salad, a few spoonfuls of ground flaxseed over your breakfast cereal, or an 6 ounce serving of grilled salmon would be good sources. You may want to follow the American Heart Association recommendation of having fish twice a week.

Is the Mercury in Fish Dangerous?

Mercury is a naturally occurring element, but it is also a byproduct of pollution. In high amounts, ingesting mercury can cause neurological problems. All fish and seafood contain some amount of mercury. So while it is impossible to avoid mercury entirely when eating fish and seafood, you can make lower-mercury choices.

Which Are Low-Mercury Fish?

Shrimp, canned light tuna, salmon, and pollock have the lowest mercury levels of seafood. Fish such as sardines and anchovies also contain lower levels because they are smaller sized fish with short lifespans, giving them less opportunity to ingest contaminates.

Which Are the High-Mercury Fish?

King mackerel, shark, swordfish, and tilefish are the highest mercury containing fish. Albacore tuna has more mercury than white tunas.

What if I Am Pregnant?

Mercury is most dangerous for women who may become pregnant, are pregnant or are nursing because it can accumulate in the body and harm the fetus. Similarly, young children who eat a very high mercury diet are believed to have increased risk of neurological problems. The Environmental Protection Agency (EPA) recommends that pregnant and nursing women limit their intake of high mercury fish, and eat up to 12 ounces a week of low-mercury fish and seafood.

What Other Chemicals Should I Be Concerned About?

Additional contaminates of concern are dioxins and polychlorinated biphenyls (PCBs). PCB content varies by geographic location, so you must find out where your fish comes from in order to accurately know the PCB content. The consensus of nutrition researchers is that the benefit of eating fish and seafood far outweighs any potential risk of PCBs you may consume.

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