Cod-liver oil

Also known as cod liver oil.

Last reviewed October 9, 2026 · Jump to references

What is Cod-liver oil?

In plain words

Cod-liver oil is oil from cod fish livers that contains omega-3 fats and vitamins A and D. The body breaks down the oil and uses its nutrients to build cells and support vision, bones, and immune function. Researchers study it for effects on blood fats, inflammation, and bone health, but evidence about individual nutrients does not prove the same benefits for every cod-liver oil product. Too much vitamin A or D can be harmful.

Technical definition

Cod-liver oil is a lipid mixture extracted from cod livers, containing triglycerides that supply the omega-3 fatty acids EPA and DHA, along with variable amounts of vitamins A and D. Digestion releases fatty acids for absorption; EPA and DHA enter cell membranes and influence lipid-signaling pathways, while vitamin A and active vitamin D metabolites act through nuclear receptors that regulate gene expression. It is marketed as a dietary supplement in the United States, without FDA preapproval for safety or effectiveness.

Educational information only. This page does not provide medical advice or determine whether a supplement is appropriate for you. Review supplements with a qualified healthcare professional, especially if you take medication, are pregnant, have surgery scheduled, or have a chronic medical condition.

Evidence by use

Each use is rated on its own. There is no single overall effectiveness score.