Word: vitamin
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...research that earned Wald the award began in Germany more than three decades ago, when he discovered Vitamin A in the retina. The retina is the membrane that receives the visual image from the lens and passes it on to the brain through the optic nerve...
...added pigment-again, starting with chance mutation-as a screen against harmful radiation from the sun. It is a fact that Negroes seldom have skin cancer, though its incidence is rising noticeably in the white population of the U.S. The same pigment, by filtering solar radiation, impedes synthesis of vitamin D, which prevents rickets and is manufactured from the sun's rays by the body. As early man migrated out of the tropical sun-into the green jungle, north to less torrid zones-light skin thereupon conferred an advantage by admitting more vitamin D-produc-ing sunlight...
...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...