Abstract

Natural vitamin D (D₃, cholecalciferol) reaches the body from animal sources in the diet and from endogenous skin synthesis by the action of solar ultraviolet irradiation. Vitamin D₂ (ergocalciferol) is used for fortifying proprietary foods such as margarine (and milk in the USA and Canada). These compounds have equal potency in man. A regular intake of 2.5 micrograms (100 i.u.) daily for adults and about 10 micrograms (400 i.u.) daily for children under 5 years old is usually recommended to prevent nutritional osteomalacia and rickets.