Omega-3 fatty acids are a group of polyunsaturated fatty acids that are important for a number of functions in the body. The omega-3 fatty acids EPA and DHA are found in seafood, such as fatty fish (e.g., salmon, tuna, and trout) and shellfish (e.g., crab, mussels, and oysters). A different kind of omega-3, called ALA, is found in other foods, including some vegetable oils (e.g., canola and soy). Omega-3s are also available as dietary supplements; for example, fish oil supplements contain EPA and DHA, and flaxseed oil supplements contain ALA. Moderate evidence has emerged about the health benefits of consuming seafood. The health benefits of omega-3 dietary supplements are unclear.
Here are 7 things you should know about omega-3s:
- Results of studies on diets rich in seafood (fish and shellfish) and heart disease provide moderate evidence that people who eat seafood at least once a week are less likely to die of heart disease than those who rarely or never eat seafood. The Dietary Guidelines for Americans, 2010 (3MB PDF) includes a new recommendation that adults eat 8 or more ounces of a variety of seafood per week because it provides a range of nutrients, including omega-3 fatty acids. (Smaller amounts are recommended for young children, and there are special recommendations for pregnant or breastfeeding women. See Tip #4.)
- Evidence suggests that seafood rich in EPA and DHA should be included in a heart-healthy diet; however, supplements of EPA and DHA have not been shown to protect against heart disease. In 2012, two groups of scientists analyzed the research on the effects of EPA/DHA supplements on heart disease risk. One group analyzed only studies in people with a history of heart disease, and the other group analyzed studies in people both with and without a history of heart disease. Neither review found strong evidence of a protective effect of the supplements.
- A 2012 review of the scientific literature concluded that EPA and DHA, the types of omega-3s found in seafood and fish oil, may be modestly helpful in relieving symptoms of rheumatoid arthritis. In the studies included in the review, many of the participants reported that when they were taking fish oil they had briefer morning stiffness, less joint swelling and pain, and less need for anti-inflammatory drugs to control their symptoms.
- The nutritional value of seafood is of particular importance during fetal growth and development, as well as in early infancy and childhood. Women who are pregnant or breastfeed should consume 8 to 12 ounces of seafood per week from a variety of seafood types that are low in methyl mercury as part of a healthy eating pattern and while staying within their calorie needs. Pregnant or breastfeeding women should limit the amount of white tuna (labeled as “albacore”) to no more than 6 ounces per week. They should not eat tilefish, shark, swordfish, and king mackerel because they are high in methyl mercury.
- There is ongoing research on omega-3 fatty acids and diseases of the brain and eye, but there is not enough evidence to draw conclusions about the effectiveness of omega-3s for these conditions. DHA plays important roles in the functioning of the brain and the eye. Researchers are actively investigating the possible benefits of DHA and other omega-3 fatty acids in preventing or treating a variety of brain- and eye-related conditions.
- There is conflicting evidence about whether a link might exist between the omega-3 fatty acids found in seafood and fish oil (EPA/DHA) and an increased risk of prostate cancer. Additional research on the association of omega-3 consumption and prostate cancer risk is under way.
- The bottom line: Including seafood in your diet is healthful. Whether omega-3 supplements are beneficial is uncertain. If you are considering omega-3 supplements, talk to your health care provider. It’s especially important to consult your (or your child’s) health care provider if you are pregnant or breastfeeding, if you take medicine that affects blood clotting, if you are allergic to seafood, or if you are considering giving a child an omega-3 supplement.