Fish oil, which contains omega-3 fatty acids, is a commonly used dietary supplement. Omega-3s are promoted as “healthy” fats, and research shows that foods that contain omega-3s, such as fish and other seafood, have many health benefits. However, the potential benefits of fish oil and other omega-3 dietary supplements are not as clear. Below are answers to some commonly asked questions about fish oil and omega-3s.
1. I’m confused by all of the different terms such as ALA, EPA, and DHA that are used when referring to omega-3s from fish oil, flaxseed, or other sources. What are the differences?
There are two main types of omega-3 fatty acids—“short chain” and “long chain,” named for their somewhat different chemical structures. ALA is one of the most common short-chain omega-3s, while EPA and DHA are the most common long-chain omega-3s.
Plant foods such as flaxseed, soybean, and canola oils, as well as chia seeds and black walnuts, contain ALA. Fish and other seafood—especially cold-water fatty fish such as salmon, mackerel, and tuna—contain EPA and DHA.
Most omega-3 supplements, including fish oil, krill oil, cod liver oil, and vegetarian products made from algal oil, contain EPA and DHA. Flaxseed oil supplements contain ALA. Some foods, including certain brands of eggs, yogurt, milk, and soy beverages, contain added omega-3s. You can check product labels to determine which ones.
Most research on the potential health benefits of omega-3s involves EPA and DHA. Our bodies can convert ALA into EPA and DHA, but not very well. So if you want to increase the amount of EPA and DHA you consume, you need to get them from either foods or dietary supplements. If you eat about 8 ounces per week of a variety of seafood, you are getting about 250 mg of EPA and DHA each day. A typical fish oil supplement provides about 300 mg of EPA and DHA, but doses vary widely.
2. Are fish oil supplements recommended for cardiovascular disease? What does the latest research show?
Fish oil supplements help lower triglyceride levels, but their other effects on cardiovascular disease are less clear. Studies conducted 10 to 20 years ago found that fish oil reduced the risk of some heart problems such as sudden death and stroke, especially among people with heart disease. But many recent studies have not found the same thing. Some researchers believe that changes in people’s lifestyles, such as increased use of statins and higher consumption of fish over the last 10 to 20 years, might overshadow the potential benefits of fish oil. Research clearly shows that eating fish and other seafood as part of a healthy eating pattern reduces the risk of cardiovascular disease. Therefore, experts recommend consuming 8 or more ounces per week of fish and other seafood, including some varieties that have higher amounts of EPA and DHA (such as salmon, mackerel, and tuna).
3. I am pregnant and have heard that it’s important to get DHA in addition to prenatal vitamins. Should I take a supplement, eat more fish, or both?
During pregnancy, experts recommend eating 8 to 12 ounces of a variety of seafood per week, choosing from varieties that are lower in methyl mercury. These include salmon, herring, sardines, light tuna, and trout. Pregnant women should not consume certain types of fish—such as king mackerel, shark, swordfish, and tilefish—that are high in methyl mercury.*
Some studies show that taking DHA or other omega-3 dietary supplements during pregnancy might slightly increase a baby’s weight at birth and the length of time the baby is in the womb, both of which might be beneficial. However, it is not clear whether taking these supplements during pregnancy affects a baby’s health or development. We recommend talking with your health care provider for advice.
* The U.S. Food and Drug Administration and Environmental Protection Agency have issued advice regarding eating fish. This advice will help women who are pregnant or may become pregnant—as well as breastfeeding mothers and parents of young children—make informed choices about fish that is healthy and safe to eat.