What are omega-3s?

Omega-3 fatty acids are a group of fats that occur naturally in certain foods and in the human body. They are also available as dietary supplements and are sometimes called n-3 fatty acids.

• Most scientific research has focused on two types: EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).

• EPA and DHA are primarily found in seafood, especially fatty fish such as salmon, mackerel, and tuna, as well as in shellfish and fish oil supplements.

• Another omega-3, ALA (alpha-linolenic acid), is present in plant-based sources like flaxseed, soybean, and canola oils, as well as chia seeds and walnuts.

• A large body of research has examined the possible health effects of consuming omega-3 fatty acids.

• The Dietary Guidelines for Americans 2020–2025 recommend that adults consume at least 8 ounces of a variety of seafood each week. Choosing seafood rich in EPA and DHA is encouraged. Smaller portions are advised for young children.

What dietary supplements contain omega-3s?

Omega-3 fatty acids are available in several types of supplements.

• Fish oil supplements provide EPA and DHA.

• Fish liver oil products, such as cod liver oil, supply EPA and DHA along with vitamins A and D. These vitamins vary in amount by product and may be harmful if taken in excess.

• Krill oil contains omega-3s in phospholipid form.

• Algal oil offers a vegetarian source of DHA; some formulations also include EPA.

• Flaxseed oil provides ALA.

What does the science say about seafood vs. supplements?

For certain health outcomes, eating seafood appears to provide stronger evidence of benefit than taking omega-3 supplements.

• Seafood contains additional nutrients beyond omega-3s that may contribute to its positive effects.

• Benefits may also result from replacing less nutritious foods with fish or shellfish.

• People who regularly eat seafood often have overall healthier lifestyle habits, which may influence results.

Can omega-3 supplements help to prevent heart disease and other cardiovascular events?

Some findings suggest that individuals with heart disease or elevated triglycerides may benefit from omega-3 supplementation.

• A 2020 review of 86 studies involving more than 160,000 participants found that higher intake of EPA and DHA slightly lowered the risk of coronary events and coronary death. Most studies used capsules, while others relied on dietary changes or advice.

• A 2019 meta-analysis of 13 major trials with over 127,000 participants reported that marine omega-3 supplements reduced the risk of heart attack, death from coronary heart disease, and overall coronary events.

• A review of three large trials concluded that taking 1 gram per day of omega-3 fatty acids may offer modest cardiovascular benefits for the general population.

Can omega-3s help to prevent stroke?

Eating fish and shellfish has been associated with a moderate reduction in stroke risk.

• A 2020 review of 31 trials found that increasing omega-3 supplements had little or no overall impact on stroke prevention.

• A 2021 analysis suggested low-dose supplementation did not lower stroke risk, while higher doses showed some potential benefit. However, evidence was limited.

• A 2016 evidence report indicated marine-based omega-3s might reduce the risk of ischemic stroke, but they have not been shown to decrease total stroke incidence or stroke-related deaths.

Can omega-3s help to reduce triglyceride levels?

Triglycerides are fats in the bloodstream, and high levels increase the risk of heart disease. Lifestyle measures are the first line of treatment, and medications may also be necessary.

• A 2020 review of 23 studies found that EPA and DHA reduced triglyceride levels by about 15 percent, without affecting body fat or other blood lipids.

• Certain prescription omega-3 products are approved for patients with very high triglycerides. These medications differ from over-the-counter supplements in formulation, testing, and regulation, and their effects may not be identical.

Are omega-3s helpful for depression?

Research results are mixed regarding the effectiveness of omega-3 supplements for depression.

• A 2021 review of 35 studies concluded that any potential benefit appears small and based on low-quality evidence.

• Some analyses suggest EPA may be more effective than DHA and that omega-3s may work best as an addition to antidepressant therapy rather than a replacement. More rigorous studies are needed.

• A 2019 review examining use during pregnancy found possible reductions in depressive symptoms during pregnancy but not after childbirth.

• Depression is a serious condition. Anyone experiencing symptoms should seek guidance from a qualified health care provider.

Are omega-3s helpful for attention-deficit hyperactivity disorder (ADHD)?

Some evidence links lower omega-3 intake and higher omega-6 intake with ADHD, but supplement research has produced inconsistent findings.

• A 2023 review of 36 studies found no clear evidence that omega-3 or combined polyunsaturated fatty acid supplements significantly improve ADHD symptoms in children or adolescents. The authors emphasized the need for larger, well-designed trials.

Can omega-3s help to prevent Alzheimer’s disease (AD) or cognitive impairment?

Higher seafood consumption has been associated with a lower risk of cognitive decline.

• A 2022 review suggested omega-3s may help protect cognitive function in healthy individuals but showed no benefit for those already diagnosed with Alzheimer’s disease.

• A 2018 review indicated possible benefit during early stages of cognitive impairment, though evidence was insufficient to support omega-3s as treatment.

• Genetic differences, such as carrying the APOE4 gene, may influence how individuals respond to DHA supplementation.

Are omega-3s helpful for other conditions affecting the brain, nervous system, or mental health?

Research on omega-3s for neurological and psychiatric conditions shows varying outcomes.

• Some studies in multiple sclerosis suggest improvements in relapse rates, inflammation, and quality of life.

• Research in autism spectrum disorders has not demonstrated clear benefits.

• Omega-3s, particularly EPA, may reduce certain symptoms in borderline personality disorder and schizophrenia, though long-term effectiveness remains uncertain.

• Evidence across these conditions is inconsistent, and more high-quality studies are needed.

Can omega-3s help to prevent age-related macular degeneration and other eye diseases?

Age-Related Macular Degeneration (AMD)

AMD is a leading cause of vision loss in older adults.

• Large clinical trials found that specific combinations of vitamins, antioxidants, and zinc slowed progression in high-risk individuals, but adding EPA and DHA did not provide extra benefit.

• Other studies have not shown omega-3 supplements to slow AMD progression.

Dry Eye Disease

Dry eye disease can cause irritation, blurred vision, and light sensitivity.

• Smaller studies suggested symptom relief with omega-3 supplementation.

• A 2022 review indicated possible improvement, though study limitations were noted.

• A large NIH-sponsored trial found omega-3 supplements were no more effective than placebo over one year, and follow-up results were similar.

Retinitis Pigmentosa

• Retinitis pigmentosa is a rare inherited disorder affecting the retina. Limited studies have not shown clear benefits from omega-3 supplementation.

Can omega-3s help to relieve symptoms of rheumatoid arthritis?

• A 2022 review found that diets rich in omega-3s may reduce joint pain and swelling and could complement standard treatments.

• A 2021 review reported lower pain levels in people consuming omega-3–rich diets, although evidence quality was low.

• Individuals with rheumatoid arthritis should consult their health care providers before altering prescribed therapies.

Are omega-3s beneficial for infant development?

• Seafood provides nutrients important for early development. Pregnant or breastfeeding women are advised to consume 8–12 ounces of low-mercury seafood weekly.

• A 2020 review found limited evidence that omega-3 supplementation during pregnancy improves children’s cognitive development, with insufficient data for other developmental outcomes.

• A 2018 review reported fewer preterm births and low birth weight infants among women who received long-chain omega-3 supplements.

• A 2016 evidence review found slightly higher birth weights and longer pregnancies with supplementation, but no clear effects on premature birth or long-term developmental outcomes.

Are omega-3 supplements safe?

Omega-3 supplements are generally well tolerated. Mild side effects may include unpleasant taste, bad breath, odor changes, headache, heartburn, nausea, or diarrhea.

NCCIH-Funded Research

Current research supported by NCCIH includes:

• Long-term follow-up of participants in a large omega-3 and vitamin D trial.

• Testing EPA-enriched supplements as an addition to treatment for resistant depression.

• Investigating how genetic differences affect responses to omega-3s in relation to heart disease risk factors.

More To Consider

Discuss any complementary health approaches, including omega-3 supplements, with your health care providers. Shared decision-making helps ensure safe and informed choices.

For More Information

NCCIH Clearinghouse

Provides information about complementary and integrative health approaches and related research resources. It does not offer medical advice.

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

Offers evidence-based information on dietary supplements and supports research and public education initiatives.

NIH Clinical Research Trials and You

Provides educational resources about clinical trials and participation.

MedlinePlus

Supplies reliable health information from government and medical organizations.

Research Portfolio Online Reporting Tools (RePORTER)

A searchable database of federally funded research projects.

Know the Science

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PubMed®

A database of scientific and medical literature maintained by the National Library of Medicine.

Key References

A selection of systematic reviews, meta-analyses, and major clinical trials on omega-3 fatty acids and their effects on cardiovascular health, mental health, eye disease, rheumatoid arthritis, pregnancy outcomes, and cognitive function supports the information summarized in this publication.

Other References

Additional peer-reviewed articles and government reports provide further context on omega-3 fatty acids and their potential health effects across a range of medical conditions.

Acknowledgments

This publication was reviewed by scientific experts for accuracy and clarity. It is intended for informational purposes and is in the public domain.

This material does not replace professional medical advice. Always consult a qualified health care provider regarding medical decisions. Mention of specific products or therapies does not constitute endorsement.