Vitamin D : Deficiency , Diversity and Dosage Andrew

Introduction Vitamin D was first isolated from tuna fish oil in 1936, and synthesized in 1952. It is a prohormone sterol which the body manufactures, given sunlight, from 7-dehydrocholesterol. Vitamin D3 (C27H44O, cholecalciferol) is the form we and other animals make, and what is found in fish liver oil. Oddly enough, fish cannot synthesize vitamin D. They get theirs low on the food chain from planktonic algae; big fish eat little fish; we eat big fish. Vitamin D2 (C28H44O) is made from ergosterol, not cholesterol, and consequently is called ergocalciferol. This is the form that is found in plants. Vitamin D2 man-made by ultraviolet irradiation of ergosterol is the form usually added to milk and found in most American supplements. Vitamin D3 is more commonly used as a supplement in Europe. As a curiosity, reindeer lichen contains both vitamin D2 and D3. Although D2 and D3 differ by a single carbon atom, there is evidence that D3 is more efficiently utilized in chicks and, more to the point, in humans. “The assumption that vitamins D2 and D3 have equal nutritional value is probably wrong and should be reconsidered.” There are two commercial sources of natural vitamin D3: fish liver oil and an oil extracted from wool. “If a label lists ‘vitamin D3 (cholecalciferol)’ then it is from wool oil. This is considered a vegetarian source (the animal is not harmed, just sheared), but not vegan. Fish liver oil will be in parentheses if it is the source.” Animals can obtain vitamin D from licking their fur, and in humans, rickets can be successfully treated by rubbing cod liver oil into the skin.