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Vitamin D and Osteopoirosis Vitamin D is an essential part of our diet from infancy through adulthood. It is metabolized in the liver and kidneys to 1,25-dihydroxyvitamin D, which is the active form of the vitamin. This vitamin has a major role in the absorption and metabolism of calcium. Of course, calcium intake must be maintained for vitamin D to be an effective part of your diet, and there are other factors that are necessary for the growth and preservation of bone.Vitamin D can be obtained in the diet and is plentiful in dairy products (through fortification), eggs, and fish. Most dietary vitamin D in developed countries comes in the form of fortification of infant formulas, dairy products, cereals, and other fortified foods and vitamin supplements. Exposure of the skin to sunlight also converts a cholesterol compound to vitamin D. There is little standardization for fortification of foods and it is difficult to quantify the amount of vitamin D conversion in the skin, so assessment of dietary vitamin D intake is generally inaccurate. A vitamin D metabolite, 25-hydroxyvitamin D, can be measured in the serum which gives and estimate of the stores of vitamin D in the body and indirectly the amount of vitamin D ingested in the diet. In the absence of vitamin D severe bone disease, rickets and osteomalacia, can occur but is unusual, except in exclusively breast fed babies in the northern latitudes during the winter months. Much more common is an inadequate amount of vitamin D in the diet. This is particularly common in older individuals who do not drink or eat vitamin D fortified beverages and foods. <page 1> <page 2> References: Chapuy MC, Arlot ME, Duboeuf F, et al. 'Vitamin D3 and calcium to prevent hip fracture in elderly women.' N Engl J Med 1992; 327:1637-42. Dawson-Hughes B, Harris SS, Krall EA, Dallal GE. 'Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age and older.' N Engl J Med 1997; 337:670-6. Filosa A, Di Maio S, et al. 'Longitudinal monitoring of bone mineral density in thalassemic patients, Genetic structure and osteoporosi.' Acta Paed 1997; 86:342-6. Moulas A, Challa A, et al. 'Vitamin D metabolites (25-hydroxyvitamin D, 24,25-dihydroxyvitamin D and 1,25-dihydroxyvitamin D) and osteocalcin in beta-thalassemia.' Acta Paed 1997; 86:594-9. Utiger RD. 'The need for more vitamin D.' N Engl J Med 1998; 338:828-9. |
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