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

The omega-3 fatty acids in fish are good for your heart. Find out why the heart-healthy benefits of eating fish usually outweigh any risks.

By Mayo Clinic Staff

If you're worried about your heart health, eating at least two servings of fish a week could reduce your 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. Find out 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 your 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 your risk of strokes and heart failure risk
  • Reducing irregular heartbeats

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

Does it matter what kind of fish you eat?

Although 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. Women who are pregnant, plan to become pregnant or are breast-feeding and young children should avoid eating fish with the potential for high levels of mercury contamination.

  • 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.
  • Women who are pregnant, plan to become pregnant or are breast-feeding should eat up to 12 ounces of seafood per week from a variety of choices that are lower in mercury contamination.
  • Children should also 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 prepared. 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?

For most adults, the risk of getting too much mercury or other contaminants from fish is generally outweighed by the health benefits of omega-3 fatty acids. The main types of 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 accumulates in lakes, rivers and oceans, which turns up in the food 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

Should anyone avoid eating fish because of the concerns over mercury or other contaminants?

If you eat enough fish containing mercury, the toxin can accumulate in your body. Although it's unlikely that mercury would cause any health concerns for most adults, it is particularly harmful to the development of the brain and nervous system of unborn children and young children.

The FDA and the Environmental Protection Agency (EPA) recommend that the following groups limit the amount of fish they eat:

  • Women who are pregnant or trying to become pregnant
  • Breast-feeding mothers
  • Young children

Pregnant women or women who are trying to become pregnant, breast-feeding mothers, and children 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, and limiting the amount they 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)

Are there any other concerns related to eating fish?

Some recent studies have linked high levels of omega-3 fatty acids in the blood to an increased risk of prostate cancer. But other studies have suggested that omega-3 fatty acids might prevent prostate cancer.

None of these studies were conclusive, so more research needs to be done. In the meantime, talk with your doctor 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 because of the antibiotics, pesticides and other chemicals used in raising farmed fish. However, the FDA has found that the levels of contaminants in commercial fish do not seem to cause harmful effects to 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 appears to provide more heart-healthy benefits than does using supplements. Other nonfish food options that do contain some omega-3 fatty acids include:

  • 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

However, similar to supplements, the evidence of heart-healthy benefits from eating these foods isn't as strong as it is from eating fish.

Sept. 28, 2019 See more In-depth