Advert for Scott's Emulsion of Pure Cod Liver Oil

Cod liver oil was first used by the fishing communities of Scotland, Iceland, Norway and Greenland to protect them from intense cold. During the 1890s, it began to be used to treat malnourished children who suffered from rickets, a type of Vitamin-D deficiency. Because of the oil's Vitamin D content, daily doses were also advised to relieve rheumatism, aching muscles and stiff joints. A full experimental link between cod liver oil and the treatment of Vitamin-D deficiency was not made, however, until 1922.