Human diseases rickets

The existence of vitamin D was actually discovered as a consequence of human disease. Rickets has been known almost since antiquity and was quite clearly described in the literature around 1600. Glisson and Whistler are credited with the first clear description of the disease rickets which we now know is the childhood counterpart of vitamin D deficiency disease. With the industrial revolution which took place in the latter part of the 19th century came the changing of an agrarian... 

Vitamin D [1406-12-2] is a material that is formed ia the skin of animals upon kradiation by sunlight and serves as a precursor for metaboUtes that control the animal s calcium homeostasis and act ki other hormonal functions. A deficiency of vitamin D can cause rickets, as weU as other disease states. This tendency can be a problem wherever animals, including humans, especially kifants and children, receive an kiadequate amount of sunshine. The latter phenomenon became prevalent with the advent of the kidustrial revolution, and efforts to cute rickets resulted ki the development of commercial sources of vitamin D for supplementation of the diet of Hvestock, pets, and humans. 

The small family of molecules known as vitamin D is essential for bone health and other aspects of human well-being. Rickets and osteomalacia are vitamin D deficiency diseases. 

A lack of vitamin D causes rickets, a disease of humans and other animals in which the bones are soft, deformed, and poorly calcified. Rickets was recognized by some persons to result from a dietary deficiency well over a hundred years ago, and the use of cod liver oil to prevent the disease was introduced in about 1870. By 1890 an association of rickets with a lack of sunlight had been made. 

The precursors of vitamins D2 and D3 are ergosterol and 7-dehydrocholesterol, respectively. These precursors or provitamins can be converted into the respective D vitamins by irradiation with ultraviolet light. In addition to the two major provitamins, there are several other sterols that can acquire vitamin D activity when irradiated. The provitamins can be converted to vitamin D in the human skin by exposure to sunlight. Because very few foods are good sources of vitamin D, humans have a greater likelihood of vitamin D deficiency than of any other vitamin deficiency. Enrichment of some foods with vitamin D has significantly helped to eradicate rickets, which is a vitamin D deficiency disease. Margarine and milk are the foods commonly used as carrier for added vitamin D. 

Normally, it would seem unusual to expose food to ultraviolet (UV) radiation before trying to isolate a nutrient, but starting in the 1890s reports indicated that once exposed to high levels of sunshine, humans were unlikely to develop rickets. Scientists now know that UV exposure is essential for the body to produce cholecalciferol from cholesterol. See Figure 1 for the structures of cholesterol and cholecalciferol. Cholesterol is the steroid lipid often associated with heart disease when too much is present small amounts of cholesterol are needed to make cholecalciferol and a host of other steroid hormones. Since humans can manufacture all the cholecalciferol needed for good health from exposure to sunshine, vitamin D is commonly referred to as the sunshine vitamin. 

The incidence of scurvy in humans is difficult to evaluate because a good clinical test for early diagnosis is not available. Furthermore, the disease, at least in children, is often confused with rickets. Only a few years ago, 11% of all the children autopsied during a 10-year period at the Johns Hopkins Hospital presented histological changes in bone characteristic of scurvy. The frequency in adults is unknown. 

We noted above that small amounts of ultraviolet light are required for the activation of vitamin D. This interesting reaction occurs by a [1,7] suprafacial rearrangement. Vitamin D is a necessary part of the human diet for bone growth. Inadequate amounts of this vitamin result in inadequate calcification of bones. This condition in children is called rickets. The disease in adults is called osteomalacia. In spite of a dietary vitamin D deficiency, it is known that an individual may generate vitamin D since sunlight can activate a Vitamin D precursor. But in northern climates where the days are short in the winter, and one s skin is covered, it is not possible to produce enough vitamin D to make up for dietary deficiencies. 

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