Omega-3 in fish: How eating fish helps your heart

If you're worried about your heart health, eating at least two servings of fish a week could reduce your risk of heart disease.

The American Heart Association recommends eating fish rich in unsaturated fats at least twice a week. All fish are a good source of protein, vitamins and minerals. But fatty fish contain omega-3 fatty acids. Omega-3s and other nutrients in fish may improve heart health. They also may lower the risk of dying of heart disease.

Some people may worry about mercury or other contaminants in fish. But the benefits of eating fish as part of a healthy diet usually outweigh the possible risks of exposure to contaminants. Learn how to balance these concerns with adding a healthy amount of fish to your diet.

What are omega-3 fatty acids, and why are they good for my heart?

Omega-3 fatty acids are a type of unsaturated fatty acid. They may lower inflammation in the body. Inflammation in the body can hurt blood vessels. Blood vessel damage may lead to heart disease and stroke.

Omega-3 fatty acids may:

• Keep the heart healthy by slightly lowering blood pressure.
• Lower levels of fats called triglycerides in the blood.
• Lower the risk of irregular heartbeats.

Try to eat at least two servings a week of fish, especially fish that's rich in omega-3 fatty acids. Doing so appears to reduce the risk of heart disease, particularly sudden cardiac death.

Does it matter what kind of fish I eat?

Many types of seafood contain small amounts of omega-3 fatty acids. Fatty fish contain the most omega-3 fatty acids and seem to benefit the heart the most.

Good omega-3-rich fish options include:

• Salmon.
• Sardine.
• Atlantic mackerel.
• Cod.
• Herring.
• Lake trout.
• Canned, light tuna.

How much fish should I eat?

The U.S. Food and Drug Administration (FDA) recommends fish as part of a healthy diet for most people. But people in some groups should limit how much fish they eat.

Most adults should eat two servings of omega-3-rich fish a week. A serving size is 4 ounces (113 grams) or about the size of a deck of cards.

If you are pregnant, are planning to get pregnant or are breastfeeding, do not eat fish that's typically high in mercury. This includes shark, swordfish, king mackerel and tilefish. Limit the amount of other fish you eat to:

• No more than 12 ounces (340 grams) of fish and seafood in total a week.
• No more than 4 ounces (113 grams) of albacore tuna a week.

You can still get heart-healthy benefits from a variety of seafood and fish that are typically low in mercury, such as salmon and shrimp.

Young children also should not eat fish that contain potentially high levels of mercury. Kids should eat fish from choices lower in mercury once or twice a week. The serving size of fish for kids younger than age 2 is 1 ounce (28 grams) and increases with age.

To get the most health benefits from eating fish, pay attention to how it's cooked. For example, grilling, broiling or baking fish is a healthier option than is deep-frying.

Does mercury contamination outweigh the health benefits of eating fish?

If you eat a lot of fish containing mercury, the toxin can build up in your body. It's unlikely that mercury would cause any health concerns for most adults. But mercury is very harmful to the development of the brain and nervous system of unborn babies and young children.

For most adults, the benefits of omega-3 fatty acids outweigh the risk of getting too much mercury or other toxins. The main toxins in fish are mercury, dioxin and polychlorinated biphenyls, also called PCBs. The amounts of toxins depend on the type of fish and where it's caught.

A little bit of mercury occurs naturally in the environment. But pollution from factories and other industries can produce mercury that collects in lakes, rivers and oceans. That pollution can end up in the food that fish eat.

When fish eat this food, mercury builds up in their bodies. Large fish that are higher in the food chain eat smaller fish. So large fish get even more mercury. The longer a fish lives and eats, the larger it grows and the more mercury it can collect. Fish that may contain higher levels of mercury include:

• Shark.
• Tilefish.
• Swordfish.
• King mackerel.

Are there any other concerns related to eating fish?

Some studies say high levels of omega-3 fatty acids in the blood increase the risk of prostate cancer. But other studies say high levels of omega-3s might prevent prostate cancer.

None of these studies was definite. More research is needed. Talk with a health care professional about what this potential risk might mean to you.

Some researchers also are concerned about eating fish grown on farms as opposed to fish caught in the wild. Antibiotics, pesticides and other chemicals may be used in raising farmed fish. But the FDA says the levels of contaminants in farmed fish don't seem to be bad for health.

Can I get the same heart benefits by taking an omega-3 supplement or eating other foods that contain omega-3 fatty acids?

Eating fish rich in omega-3 fatty acids and other nutrients seems to be better for the heart than just using supplements. If you don't want or like fish, other foods that have some omega-3 fatty acids are:

• Flaxseed and flaxseed oil.
• Walnuts.
• Canola oil.
• Soybeans and soybean oil.
• Chia seeds.
• Green leafy vegetables.
• Cereals, pasta, dairy and other food products with added omega-3 fatty acids.

But the heart-healthy benefits from eating these foods do not seem to be as strong as those from eating fish.