Sunshine vitamin

Actually, neither vitamin D2 nor D3 is present in foods. Rather, foods contain the precursor molecules 7-dehydrocholesterol and ergosterol. In the presence of sunlight, however, both precursors are converted under the skin to the active vitamins, hence the nickname for vitamin D, the "sunshine vitamin. 7... 

The definition of vitamin D deficiency is a condition where the concentration of 25-hydroxy vitamin Dj in the blood serum occurs at 12 ng/ml or less. Prolonged deficiency can result in two diseases, namely rickets (in children) and ostettmalacia (in adults). Vitamin D deficiency tends to occur in those who do not get enough exposure to sunlight and who also fail to eat foods that are rich in vitamin D. In an ideal world, where everyone was regularly exposed to sunshine, vitamin D would never be classified as a vitamin,... 

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. 

There is considerable evidence that vitamin D is a potent regulator of the immune system and promotes normal cell growth. D is best known as the sunshine vitamin and has been used for decades to cure childhood rickets. In its active form, this fat-soluble vitamin changes to the steroid hormone calcitriol, which helps maintain blood calcium levels. Some evidence suggests that D decreases the risk of many common cancers (especially breast, ovarian, colon, and prostate), type-2 diabetes, autoimmune diseases, and high blood pressure. ... 

Vitamin D is the sunshine vitamin . It was originally discovered as a crude mixture called vitamin Dj (no longer available as a supplement). Ergosterol, the plant equivalent of cholesterol, is converted to vitamin D2 by ultraviolet light. Vitamin D3 (cholecalciferol) is formed in the skin from 7-dehydrocholesterol (an intermediate in the cholesterol biosynthesis pathway) in the presence of ultraviolet light, which opens the B-ring of the steroid nucleus (Fig. 51.3). Cholecalciferol is successively hydroxylated first in the liver forming 25-hydroxycholecalciferol (25-HCC) and then in the kidney to form the most active form 1,25-dihydroxy cholecalciferol (1,25-DHCC), also known as calcitriol. 

Chesney, R. W. 2012b. Theobald Palm and his remarkable observation How the sunshine vitamin came to be recognized. Nutrients 4 42—51. 

Cholecalciferol (vitamin D3, I) is formed from cholesterol in the skin through photolysis of 7-dehydrocholesterol (provitamin D3) by ultraviolet light ( sunshine vitamin cf. 3.8.2.2.2). Similarly, vitamin D2 (ergocalciferol, II cf. Formula 6.2) is formed from ergosterol. 

In this chapter, we will see why vitamin D is called the sunshine vitamin and why the reaction that causes skin cancer requires sunlight. We will also look at the reaction that causes fireflies to give off light. 

The importance of vitamin D—the sunshine vitamin—in human nutrition lies in the role of regulating calcium and phosphorus metabolism. Vitamin D promotes intestinal absorption of calcium and phosphorus and influences the process of bone mineralization. In the absence of vitamin D, mineralization of bone matrix is impaired, resulting in rickets in children and osteomalacia in adults. Although rickets is rare in the United States, it is still prevalent in many countries. 

Vitamin D is unique among the vitamins in two respects (1) it occurs naturally in only a few common foods (mainly in fish oils, and a little in liver, eggs, and milk), and (2) it can be formed in the body by exposure of the skin to ultraviolet rays of the sun—light of short wavelength and high frequency hence, it is known as the sunshine vitamin. 

Fig. V-45. Factors that inhibit the sunshine vitamin—that screen out light and prevent the formation of vitamin D. Note, too, top food sources of vitamin D.

By the late 1920s, it had been established that rickets could t)e prevented and cured by exposure to direct sunlight (ever since, vitamin D has been popularly called the sunshine vitamin), by irradiation with ultraviolet light, by feeding irradiated food, or by feeding cod-liver oil. Eater, the natural vitamin D offish liver oils was identified as the same suE)stance that is produced in the skin by irradiation. 

A Summary of Rules for Pericycllc Reactions A Deeper Look—Vitamin D, the Sunshine Vitamin... 

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