Fish Oil

Does fish oil lower cholesterol?

Triglycerides and cholesterol are different measurements. A Cochrane review of 86 trials involving 162,796 people found that increasing EPA and DHA reduced triglycerides by about 15%, without a clear effect on other blood lipids. Most trials used capsules, and each lasted at least a year. 1

A smaller crossover trial, in which participants received both treatments in separate periods, compared EPA-rich with DHA-rich fish oil in 30 adults with normal lipid levels. Participants received 12 g of oil daily for eight weeks per treatment period; that is oil weight, not 12 g of EPA and DHA. Both preparations reduced triglycerides from baseline without changing cholesterol concentrations. The study compared two active oils, so it does not establish a benefit over placebo. 2

Will daily fish oil prevent a first heart problem?

VITAL tested a daily 1 g formulation in 25,871 US adults, men aged at least 50 and women at least 55. Over a median 5.3 years, the primary combined outcome of heart attack, stroke or cardiovascular death was not significantly reduced compared with placebo. 3

Heart attacks considered separately were less frequent, a secondary finding worth keeping in view. It does not overturn the main result or show that every component of cardiovascular risk improved. The broader Cochrane review also found little or no effect on overall cardiovascular events, while allowing for a small possible reduction in coronary events. 1 3

Why do prescription omega-3 studies look different?

In REDUCE-IT, 4 g daily of prescription icosapent ethyl, a purified EPA product, reduced cardiovascular events in selected high-risk patients already taking statins. STRENGTH tested a different 4 g EPA/DHA formulation in high-risk patients and found no cardiovascular benefit. Formulation, population and the different placebo oils complicate comparisons. These are specific treatments and trial conditions, not interchangeable evidence for ordinary fish-oil capsules. 4

Why are researchers studying memory?

A small trial enrolled 21 adults aged 62 to 80 who reported memory concerns but did not have dementia or mild cognitive impairment. Over 24 weeks, 2.4 g EPA plus DHA daily was compared with corn oil. Researchers observed increased activation in a brain region during a memory task and an association with better working-memory performance. 5

This provides a reason to investigate brain function further. With only 21 participants and a task-based brain-imaging outcome, it cannot establish prevention of dementia or a reliable improvement in everyday memory. 5

Is more fish oil better for sore knees?

A two-year trial in 202 people with knee osteoarthritis compared 4.5 g omega-3 daily with 0.45 g in a fish-oil and sunola-oil mixture. The lower-dose group had better pain and function scores at two years. Cartilage-volume loss did not differ between groups. 6

Because both groups received active oil mixtures and there was no placebo group, this trial cannot tell us how either compares with no supplementation. It does answer one narrower question: the higher dose did not perform better. 6

Scope of this guide

This page does not assess fish oil as a treatment for skin complaints, brain fog or immune disorders.