Vitamin D
Vitamin D is really a pro-hormone, and its active form is the hormone 1,25-dihydroxycholecalciferol [1,25 (OH)2D3]. The two compounds with vitamin D activity are ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is found in ergot, a fungus growth on cereals, and vitamin D3 is formed when the skin is exposed to sunlight. The vitamins are also found in yeast and the oil of fishes. Vitamin D is fat-soluble, and requires the presence of bile salts in order to be absorbed from the intestines. Vitamin D is essential for the absorption and transport of phosphorous and calcium, and it promotes normal bone mineralisation. Deficiencies result in malformation of the bone structure in growing children, a condition known as rickets.
Since vitamin D does not occur in plants per se, it is possible to develop shortages of this vitamin if exposure to the sun is minimal. Vegans living in sunshine-poor areas should thus provide some form of supplementation to children and infants in particular. Nutritional rickets may occur in infants if the nursing mothers are themselves deficient in vitamin D.8 It is therefore, advisable for nursing mothers, in sunshine-poor areas, to also take a vitamin D supplement. Margarines are normally fortified with vitamin D, but if oils and margarines are
avoided, then supplementation through tablets seems desirable in sunshine poor areas.