Cod liver oil

Cod liver oil is a dietary supplement derived from liver of Atlantic cod (Gadus morhua). As with most fish oils, it contains the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and also vitamin A and vitamin D.

Historically, it was given to children in the United States in the 19th century as a patent medicine and by the end of the century was being praised by doctors in medical journals. After it was shown, in 1920, that vitamin D deficiency was the cause of rickets, cod liver oil was given as a rich source of vitamin D.