Supplements

Omega-3 Fish Oil

EPA and DHA fatty acids from fish oil, covered by the NIH Office of Dietary Supplements’ professional fact sheet.

Omega-3 fatty acids are polyunsaturated fats. The forms most studied in supplements are EPA and DHA, found in oily fish and fish-oil capsules; a third form, ALA, comes from plant sources such as flaxseed and walnuts and is only converted to EPA and DHA in small amounts, according to the National Institutes of Health Office of Dietary Supplements (ODS).

What published research reports

The ODS health-professional fact sheet reports that omega-3s are structural components of cell membranes — DHA is especially concentrated in the retina and brain — and that adequate intake is associated in the research it reviews with cardiovascular measures such as lower triglycerides. It notes that evidence for many other claimed benefits is mixed, and that large trials of supplementation in people already eating adequate diets have often shown smaller effects than observational studies suggested. The fact sheet lists common intakes, reports that the FDA considers supplements providing up to 5 g per day of combined EPA and DHA safe when used as directed, and notes mild side effects such as an unpleasant aftertaste or gastrointestinal discomfort. It also advises that people on anticoagulant medication consult a clinician about high doses.