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Omega-3 Supplements: In Depth

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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.

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.

What Do We Know About the Effectiveness of Omega-3s?

Conditions Affecting the Circulatory System

Conditions Affecting the Brain, Nervous System, or Mental Health

Eye Diseases

Other Conditions

What Do We Know About the Safety of Omega-3s?

  • Side effects of omega-3 supplements are usually mild. They include unpleasant taste, bad breath, bad-smelling sweat, headache, and gastrointestinal symptoms such as heartburn, nausea, and diarrhea.
  • Several large studies have linked higher blood levels of long-chain omega-3s with higher risks of prostate cancer. However, other research has shown that men who frequently eat seafood have lower prostate cancer death rates and that dietary intakes of long-chain omega-3s aren’t associated with prostate cancer risk. The reason for these apparently conflicting findings is unclear.
  • Omega-3 supplements may interact with drugs that affect blood clotting.
  • It’s uncertain whether people with seafood allergies can safely take fish oil supplements.

NCCIH-Funded Research

NCCIH is supporting research on omega-3s.

More To Consider

Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

For More Information

NCCIH Clearinghouse

The NCCIH Clearinghouse provides information on NCCIH and complementary and integrative health approaches, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

Toll-free in the U.S.: 1-888-644-6226

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1-866-464-3615

Website: https://nccih.nih.gov/

Email: info@nccih.nih.gov (link sends e-mail)

Office of Dietary Supplements (ODS), National Institutes of Health (NIH)

ODS seeks to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, supporting research, sharing research results, and educating the public. Its resources include publications (such as Dietary Supplements: What You Need to Know), fact sheets on a variety of specific supplement ingredients and products (such as vitamin D and multivitamin/mineral supplements), and the PubMed Dietary Supplement Subset.

Information on omega-3 fatty acids

Website: https://ods.od.nih.gov/

Email: ods@nih.gov (link sends e-mail)

PubMed®

A service of the National Library of Medicine, PubMed® contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. For guidance from NCCIH on using PubMed, see How To Find Information About Complementary Health Approaches on PubMed.

Website: https://pubmed.ncbi.nlm.nih.gov/

NIH Clinical Research Trials and You

The National Institutes of Health (NIH) has created a website, NIH Clinical Research Trials and You, to help people learn about clinical trials, why they matter, and how to participate. The site includes questions and answers about clinical trials, guidance on how to find clinical trials through ClinicalTrials.gov and other resources, and stories about the personal experiences of clinical trial participants. Clinical trials are necessary to find better ways to prevent, diagnose, and treat diseases.

Website: https://www.nih.gov/health-information/nih-clinical-research-trials-you

Research Portfolio Online Reporting Tools Expenditures & Results (RePORTER)

RePORTER is a database of information on federally funded scientific and medical research projects being conducted at research institutions.

Website: https://projectreporter.nih.gov/reporter.cfm

MedlinePlus

To provide resources that help answer health questions, MedlinePlus (a service of the National Library of Medicine) brings together authoritative information from the National Institutes of Health as well as other Government agencies and health-related organizations.

Information on dietary fats (including omega-3s)

Website: https://www.medlineplus.gov/

Key References

Acknowledgments

NCCIH thanks D. Craig Hopp, Ph.D., and David Shurtleff, Ph.D., NCCIH, for their contributions to the 2018 update of this publication.

This publication is not copyrighted and is in the public domain. Duplication is encouraged.

NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your health care provider(s). We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.

Last Updated: May 2018