Word: ultraviolet
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Dates: during 1960-1969
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Loomis points out in the journal Science that vitamin D is no ordinary vitamin. Unlike the others, it occurs in virtually no natural foods.* It is synthesized in the skin under the influence of ultraviolet rays. The body needs vitamin D if it is to process calcium from food to make bone. Consequently, children need proportionately more vitamin D for their growing bones, and a D deficiency causes rickets...
...black skins. Many anthropologists have argued that dark skin evolved as a protection against sunburn and skin cancer. On the contrary, says Loomis: dark skin came first, and light skin evolved as a protection against a deficiency of vitamin D. Black skin allows only 3% to 36% of ultraviolet rays to pass, while white skin passes 53% to 72%. As early man moved north from the equatorial region, beyond the 40th parallel (roughly, the latitude of Madrid and Naples), Loomis argues, he got into a zone where black skin filters out too much ultraviolet...
...cells are stimulated to produce more melanin-and a suntan. The black races (Negro, Bushman-Hottentot and Australoid), with a more abundant supply of melanin, are in effect, perpetually tanned. Members of the white race are transparent-skinned in winter, when they must make the most of the limited ultraviolet avail able to synthesize vitamin D, but they take a tan in summer, when they might suffer from an excess. There are other bits of confirmatory evidence: the only relatively dark-skinned people in high latitudes are the Eskimos, who get all the vitamin D they need from fish-liver...
...carries some in his hand throughout life. Babies of all races are lighter than adults, presumably reflecting nature's provision for early vitamin D needs. And people of all races have pale, unpigmented palms and soles. Since these parts have extra keratin and are not exposed to ultraviolet, they need no melanin protection against excess vitamin D synthesis...
...Exceptions: the liver oils of some fish, notably cod and halibut; egg yolks (small quantities) and milk (minute amounts). Milk and many other foods are now "vitamin D enriched" by ultraviolet irradiation...