What are the side effects of omega 3 capsules?

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

Heart Disease



Conditions Affecting the Brain, Nervous System, or Mental Health


Attention-Deficit Hyperactivity Disorder (ADHD)

Alzheimer’s Disease/Cognitive Impairment

Other Conditions Affecting the Brain, Nervous System, or Mental Health

Eye Diseases

Age-Related Macular Degeneration

Dry Eye Disease

Retinitis Pigmentosa

Other Conditions

Rheumatoid Arthritis

Infant Development

Miscellaneous 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 3 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 Information

Currently, topics that NCCIH-funded researchers are investigating include:

How changes in the intake of omega-3s and other fatty acids affect patients with migraine

Which patients with depression might respond to EPA

How genetic differences affect the fate of omega-3s in the body

The effects of flaxseed, which is rich in ALA, in an animal model of ovarian cancer.