What are omega-3 fatty acids used for?

What reviews found

• Triglycerides and the heart (cardiovascular health). A 2020 Cochrane review of 86 trials with 162,796 people found that EPA and DHA lowered triglycerides by about 15%.^[2] They may slightly reduce coronary heart disease events, with low certainty, and had little or no effect on all cardiovascular events, stroke or death from any cause.^[2] The large VITAL and ASCEND trials gave 1 g a day of an omega-3 supplement. In VITAL it was fish oil.^[1]
• Blood pressure. A 2022 review of 71 trials found systolic pressure about 2.6 mmHg lower at 2 to 3 g of EPA and DHA a day.^[4] The 2020 Cochrane review found little or no effect on blood pressure.^[2]
• Pregnancy (fertility). A 2018 Cochrane review of 70 trials with 19,927 women found 11% fewer preterm births, before 37 weeks, and 42% fewer early preterm births, before 34 weeks.^[3]
• Inflammation. A 2026 review of 96 trials found lower CRP, TNF-α and IL-6, three markers of inflammation in the blood. The fall was most consistent at 1 to 3 g of EPA and DHA a day.^[9]
• Muscle soreness (fitness). A 2026 review pooled 9 trials of hard exercise and found less delayed muscle soreness and better recovery of strength.^[10] The authors called the evidence as a whole equivocal.^[10]
• Mood (stress and mood). A 2021 Cochrane review of 35 studies in adults with major depression found a small benefit that is unlikely to matter in practice, with low to very low certainty.^[11]

Where reviews found little or no effect

• Memory and thinking (cognition). A 2020 review of 38 trials with 49,757 adults found little or no effect of EPA and DHA on new dementia or new cognitive impairment.^[5]
• ADHD. A 2023 Cochrane review of 37 trials in children and teenagers found high-certainty evidence of no effect on parent-rated ADHD symptoms.^[6]
• Dry eyes. In the DREAM trial, 3000 mg of EPA and DHA a day for 12 months worked no better than an olive oil placebo.^[8]
• Body weight (weight management). A 2015 review of 21 studies in adults with overweight or obesity found no effect on weight or BMI. Waist size fell a little when fish oil was combined with lifestyle changes.^[7]
• Fatty liver. A 2025 review of 20 trials found no effect on the liver enzymes AST and ALT or on liver fat measured by MRI. It found improvements only in GGT, another liver enzyme, and in liver fat seen on ultrasound.^[12]

ALA from plants

Far fewer trials tested ALA.^[1] In the 2020 Cochrane review, more ALA may slightly reduce cardiovascular events and probably slightly reduces arrhythmia, an irregular heartbeat. It made little or no difference to deaths.^[2]

Food or supplements

Many observational studies link eating fish with better health. It is hard to know whether the omega-3 causes this, or other nutrients in fish, or other healthy habits of people who eat fish.^[1] For some conditions, the evidence for seafood is stronger than the evidence for omega-3 supplements.^[13]