vitamin D

vitamin D

noun

Definition of VITAMIN D

: any or all of several fat-soluble vitamins chemically related to steroids, essential for normal bone and tooth structure, and found especially in fish-liver oils, egg yolk, and milk or produced by activation (as by ultraviolet irradiation) of sterols: as

a or vitamin D2 \-ˈdē-ˈtü\ : calciferol

b or vitamin D3 \-ˈdē-ˈthrē\ : cholecalciferol

First Known Use of VITAMIN D

circa 1921

vitamin D

noun    (Medical Dictionary)

Medical Definition of VITAMIN D

: any or all of several fat-soluble vitamins chemically related to steroids, essential for normal bone and tooth structure, and found especially in fish-liver oils, egg yolk, and milk or produced by activation (as by ultraviolet irradiation) of sterols: as a : calciferol b : cholecalciferol—called also sunshine vitamin

vitamin D

noun    (Concise Encyclopedia)

Any of a group of fat-soluble alcohols important in calcium metabolism in animals to form strong bones and teeth and prevent rickets and osteoporosis. It is formed by ultraviolet radiation (sunlight) of sterols (see steroid) present in the skin. The most important of these sterols are 7-dehydrocholesterol, formed by metabolic processes in animals, and ergosterol, present in vegetable oils. The action of sunlight on the skin converts these two compounds, respectively, to cholecalciferol (vitamin D) and ergocalciferol (vitamin D). Vitamin D is added to margarine, milk, and cereals for the benefit of those who may not get enough sunlight in winter. As little as 5 micrograms each day appear adequate for children. Because the body cannot excrete it, prolonged high intake can cause a toxic reaction including fatigue, nausea, and abnormal calcium accumulation.