Word: vitamin
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Dates: during 1960-1969
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...child against rickets, health authorities recommend a daily vitamin D intake of 400 international units (ten micrograms), which is easily obtained from milk. If the youngster's system makes more vitamin D as he plays in the sun, it is usually not enough to be dangerous. If he is given more than 20,000 units, a child becomes severely ill. In northern climes, most white adults make all the vitamin D they need from casual exposure of their face and hands to the sun and need no dietary supplement. They get ill on 100,000 units...
Origin on the Equator. The control of skin color over vitamin D synthesis, says Loomis, explains the distribution of the races of man in prehistoric and early historic times. As far as anthropologists can tell, "human beings" originated in Africa near the equator. Almost certainly, they had 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...
...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 oils. Until the 1930s, when...
...greater sharpness than have previous investigators. Every human being of every race lives through a cycle of supporting evidence for at least part of it and 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...