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

Medically reviewed by Drugs.com. Last updated on Apr 19, 2022.

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

For many years, the American Heart Association has recommended that people eat fish rich in unsaturated fats at least twice a week. The unsaturated fats in fish are called omega-3 fatty acids. Omega-3 fatty acids and other nutrients in fish may benefit heart health and reduce the risk of dying of heart disease.

Some people are concerned about mercury or other contaminants in seafood. However, 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 your heart?

Omega-3 fatty acids are a type of unsaturated fatty acid that may reduce inflammation throughout the body. Inflammation in the body can damage the blood vessels and lead to heart disease and strokes.

Omega-3 fatty acids may benefit heart health by:

Decreasing triglycerides
Lowering blood pressure slightly
Reducing blood clotting
Decreasing the risk of strokes and heart failure
Reducing irregular heartbeats

Try to eat at least two servings a week of fish, particularly 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 you 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 be the most beneficial to heart health.

Good omega-3-rich fish options include:

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

How much fish should you eat?

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

Most adults should eat at least 8 ounces or two servings of omega-3-rich fish a week. A serving size is 4 ounces or about the size of a deck of cards.

If you're pregnant, planning to become pregnant or are breastfeeding, you can still get the heart-healthy benefits of fish from a variety of seafood and fish that are typically low in mercury, such as salmon and shrimp. Limit the amount 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
No amount of any fish that's typically high in mercury (shark, swordfish, king mackerel and tilefish)

Young children also should avoid fish with potentially high levels of mercury contamination. Kids should eat fish from choices lower in mercury once or twice a week. The serving size for children younger than age 2 is 1 ounce and increases with age.

In order 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 the body. It's unlikely that mercury would cause any health concerns for most adults. But it is particularly harmful to the development of the brain and nervous system of unborn children and young children.

For most adults, the benefits of omega-3 fatty acids outweigh the risk of getting too much mercury or other contaminants. The main toxins in fish are mercury, dioxins and polychlorinated biphenyls (PCBs). The amount of toxins depends on the type of fish and where it's caught.

Mercury occurs naturally in small amounts in the environment. But industrial pollution 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 the bodies of the fish.

Large fish that are higher in the food chain eat the smaller fish, gaining higher concentrations of mercury. The longer a fish lives, 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

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

None of these studies were conclusive. More research is needed. Talk with your health care provider about what this potential risk might mean to you.

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

Can you get the same heart-healthy benefits by eating other foods that contain omega-3 fatty acids, or by taking omega-3 fatty acid supplements?

Eating fish rich in omega-3 fatty acids and other nutrients seems to provide more heart-healthy benefits than does using supplements. If you don't want or like fish, other things 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 fortified with omega-3 fatty acids

As with supplements, the heart-healthy benefits from eating these foods doesn't seem to be as strong as it is from eating fish.