What’s the Bottom Line?
How much do we know about omega-3 fatty acids (omega-3s)?
Extensive research has been done on omega-3s, especially the types found in seafood (fish and shellfish) and fish oil supplements.
What do we know about the effectiveness of omega-3 supplements?
- Research indicates that omega-3 supplements don’t reduce the risk of heart disease. However, people who eat seafood one to four times a week are less likely to die of heart disease.
- High doses of omega-3s can reduce levels of triglycerides.
- Omega-3 supplements may help relieve symptoms of rheumatoid arthritis.
- Omega-3 supplements have not been convincingly shown to slow the progression of the eye disease age-related macular degeneration.
- For most other conditions for which omega-3 supplements have been studied, the evidence is inconclusive or doesn’t indicate that omega-3s are beneficial.
What do we know about the safety of omega-3 supplements?
- Omega-3s usually produce only mild side effects, if any.
- There’s conflicting evidence on whether omega-3s might influence the risk of prostate cancer.
- If you’re taking medicine that affects blood clotting or if you’re allergic to fish or shellfish, consult your health care provider before taking omega-3 supplements.
What Are Omega-3s?
Omega-3s (short for omega-3 fatty acids) are a kind of fat found in foods and in the human body. They are also sold as dietary supplements.
Types of Omega-3s and Foods That Contain Them
- The omega-3s EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are found in seafood (fish and shellfish).
- Because of their chemical structure, EPA and DHA are sometimes referred to as long-chain omega-3s.
- A different type of omega-3, ALA (alpha-linolenic acid), is found in certain plant oils such as flaxseed, soybean, and canola oils and also in some other foods of plant origin, such as chia seeds and black walnuts.
- Most of the research discussed in this fact sheet focuses on EPA and DHA.
Supplements That Contain Omega-3s
Several types of dietary supplements contain omega-3s.
- Fish oil supplements contain EPA and DHA.
- Fish liver oil supplements, such as cod liver oil, contain EPA and DHA, and they also contain vitamins A and D, in amounts that vary from product to product. Vitamins A and D can be harmful in excessive amounts.
- Krill oil contains EPA and DHA.
- Algal oils are a vegetarian source of DHA; some also contain EPA.
- Flaxseed oil contains ALA.
Seafood vs. Supplements
- For some health conditions, the evidence for benefits from seafood (fish and shellfish) is stronger than the evidence for omega-3 supplements.
- How could this happen? Here are some possibilities:
- Seafood may provide enough omega-3s; more may not be better.
- Other nutrients in seafood besides omega-3s may play a role in its benefits.
- Some of the benefits of seafood may result from people eating it in place of less healthful foods.
- There’s evidence that people who eat seafood have generally healthier lifestyles.
The Federal Government’s Dietary Guidelines for Americans 2015–2020 recommends that adults eat 8 or more ounces of a variety of seafood (fish or shellfish) per week for the total package of nutrients seafood provides, and that some seafood choices with higher amounts of EPA and DHA be included. Smaller amounts of seafood are recommended for young children.
Use of Omega-3 Supplements in the United States
According to the 2012 National Health Interview Survey, which included a comprehensive survey on the use of complementary health approaches in the United States, fish oil supplements are the nonvitamin/nonmineral natural product most commonly taken by both adults and children. The survey findings indicated that about 7.8 percent of adults (18.8 million) and 1.1 percent of children age 4 to 17 (664,000) had taken a fish oil supplement in the previous 30 days.