| Vitamin D |
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Vitamin D is a fat soluble vitamin that is naturally found in very few foods and can also be synthesized in the body following exposure to solar ultraviolet radiation. The circulating form of vitamin D, i.e., 25-hydroxyvitamin D3 (25(OH)D3) is currently detected in serum to indicate the vitamin D status of patients. However, 25(OH)D3 is metabolically inactive and requires modification before being functional. In fact, once vitamin D is produced in the skin or consumed in food, it necessitates chemical conversion in the liver and kidneys to make 1,25 dihydroxyvitamin D3 (1,25(OH)2D3), the physiologically active form of vitamin D. Among the forms of supplemental vitamin D, the most potent one is vitamin D3 (cholecalciferol), and it is also the natural form of vitamin D produced in the skin.1-2 In the regulation of gene expression, 1,25(OH)2D3 acts solely through a single vitamin D receptor and the outcome may be either upregulation or downregulation. The key biological role of vitamin D is to sustain normal ranges of calcium and phosphorus in the blood. In collaboration with other vitamins, minerals, and hormones, vitamin D also works to advance bone mineralization. Furthermore, 1,25(OH)2D3 improves the efficacy of intestinal absorption of calcium and phosphorus, resulting in healthy bone formation and resorption. Interestingly, 1,25(OH)2D3 can further serve as a hormone by stimulating the intestines to increase calcium absorption when the body's calcium requirement is not met. Thus, a deficiency of vitamin D can contribute to fragile bones and raise the risk of bone fracture.2-4 Vitamin D May Help Prevent More Than Just Rickets and Osteomalacia Vitamin D deficiency is typically the outcome of the following occurrences:5 Limited sunlight exposure Apart from classic recommendations for bone health maintenance, a growing body of scientific evidence also suggests that scarcity of this "sunshine vitamin" may play a pivotal role in the onset of numerous conditions including: Cardiovascular disease The Recommended Intake for Vitamin D May Not Be Adequate The serum 25(OH)2D3 concentrations of at least 75–80nmol/L for optimal bone health is gaining wide acceptance, and findings from several studies that examined high-dose vitamin D supplementation indicate that the currently recommended dietary reference intake (DRI) of 200–600 IU/day for adults is significantly low compared to endogenous production through sun exposure.10-11 According to the Third National Health and Nutrition Examination Survey (NHANES III), a high prevalence of vitamin D deficiency has been observed in all races including those residing in temperate areas, and is noticeably high in African Americans. In fact, a recent survey demonstrated that 42% of African American women displayed considerably deficient levels of 25(OH)D3. Based on these data, there is a growing consensus supporting an average daily requirement for vitamin D in excess of the current DRI levels.12-13 Vitamin D Intake May Be a Small Step That Can Lead to a Big Benefit A concern for hypervitaminosis due to excessive consumption of vitamin D should not be overlooked. However, in light of mounting biomedical evidence, it appears that widespread nutritional support with vitamin D has important public health implications whereby a daily supplement can be a significant source of vitamin D, helping individuals to retain more than just healthy bones. The bottom line is that taking an adequate amount of bioactive vitamin D may help support the following: Normal cell proliferation References |