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

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

The American Heart Association recommends eating fish rich in healthy 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 pollutants in fish. But the benefits of eating fish as part of a healthy diet usually outweigh the possible risks of being exposed to pollutants. Learn how to balance these concerns with the choice to add a healthy amount of fish to your diet.

Omega-3 fatty acids are a type of healthy unsaturated fat. They may lower swelling called 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.

Try to eat at least two servings a week of fish, especially fish that's rich in omega-3 fatty acids. Doing so seems to lower the risk of heart disease, particularly sudden cardiac death. That means death due to the swift and unexpected ending of all heart activity.

Many types of seafood have small amounts of omega-3 fatty acids in them. Fatty fish have the most omega-3 fatty acids and seem to help the heart the most.

Good omega-3-rich fish options that also are low in mercury include:

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

The U.S. Food and Drug Administration, also called 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 at least two servings of omega-3-rich fish a week. A serving size is 4 ounces (113 grams) when the fish is raw or 3 ounces (85 grams) after its cooked. That's about the size of a deck of cards.

If you're pregnant, planning to get pregnant or breastfeeding, do not eat fish that's typically high in mercury. This includes tilefish from the Gulf of Mexico, also called the Gulf of America, shark, swordfish, king mackerel, marlin and orange roughy. The FDA and the U.S. Environmental Protection Agency list these fish as choices to avoid while pregnant or breastfeeding.

The agencies have a chart that ranks fish by their mercury content. Along with showing the choices to avoid, the chart lists good choices that usually have a moderate level of mercury. And the best choices typically have the least mercury.

Limit the amount of fish you eat to:

• No more than 8 to 12 ounces (227 to 340 grams) of low-mercury fish and seafood in total a week. That's 2 to 3 servings a week from the list of best choices. The amounts in ounces and grams refer to the fish before it's cooked. Options include salmon, mackerel, herring and shrimp.
• No more than 4 ounces (113 grams) of fish — before cooking — with a medium level of mercury in total a week. That's one serving from the list of good choices, which includes albacore tuna, snapper and grouper. Make this your only serving of fish for the week.

Young children also should not eat fish that may have 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 4 is 1 ounce (28 grams) before cooking, and this 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 are healthier options than is deep-frying.

If you eat a lot of fish that's higher in mercury, the toxin can build up in your body. It's not likely 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, also called fetuses, and young children.

For most adults, the good effects of omega-3s 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 have higher levels of mercury include:

• Shark.
• Tilefish from the Gulf of Mexico.
• Swordfish.
• King mackerel.
• Marlin.
• Orange roughy.

Some studies say high levels of omega-3 fatty acids in the blood may raise the risk of prostate cancer. But other studies say high levels of omega-3s might help prevent prostate cancer. Some even suggest that omega-3s from fish may help people with prostate cancer live longer.

None of these study results was definite. More research is needed. Talk with a healthcare 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 such substances in farmed fish don't seem to be bad for health.

Eating fish rich in omega-3s and other nutrients seems to be better for the heart than just using supplements. And omega-3-rich fish oil supplements may not be right for everyone. In people who don't have heart disease, regular use of the supplements may be a risk factor for atrial fibrillation. That's an irregular and often very rapid heartbeat. Yet research also suggests that fish oil supplements may have good effects in some people who already have atrial fibrillation or heart disease. It's important to talk with your healthcare professional before you start taking an omega-3 supplement.

Focus on getting omega-3s from food. 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.
• 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.