Vitamin D in Therapeutics: Past, Present and Future

Abstract

In the beginning of 20 th century vitamin D was classified as a vitamin but later considered as a prohormone ("conditional" vitamin) which influences the expression of more than 200 genes in the human body. Worldwide vitamin D insufficiency affects about 50% of the population and in India about 80% of population has vitamin D level less than normal. In India sunshine is abundant but still Indians are deprived of this sunshine vitamin. Minimal exposure to direct sunlight, staying indoors, use of sunscreen lotions, pollution, clothing, dietary and cooking habits are most important factors for vitamin D deficiency in the Indian population. Serum 25 hydroxyvitamin D level is the initial diagnostic test in patients at risk for deficiency. Treatment with either vitamin D 2 or vitamin D 3 is recommended for patients having deficiency, keeping hypervitaminosis in mind. deficiency. However nobody recognized the vital role of diet or exposure to sunlight in the prevention of this disease. Around 200 years later in 1840 a Polish physician Sniadecki found that rickets occurred in children living in the industrial centre of Warsaw but did not affect children living outside Warsaw. He found that lack of exposure to sunlight in the crowded streets of the city where sunlight is not abundant and there was considerable pollution due to the burning of coal and wood, caused the disease.In 1918 Sir Edward Mellan by discovered that beagles, which are exclusively placed inside house away from natural sunlight and fed a diet of oatmeal, developed rickets but after the addition of cod liver oil to the food cure the disease successfully. In 1921 he demonstrate "The action of fats in rickets is due to a vitamin or a specific food factor which they contain, probably the fat-soluble vitamin.In MetabolismVitamin D 3 is cholecalciferol and vitamin D 2 is ergocalciferol. On exposure to sunlight Vitamin D 3 is produced in the skin. It is derived from 7-dehydrocholesterol by ultraviolet irradiation of the skin. After ingestion vitamin D both D 2 or D 3 , incorporated into chylomicrons which get absorbed into the lymphatic system and enter the venous blood. Vitamin D that comes from the skin or diet is biologically inert and requires its first hydroxylation in the liver and second one in kidneys to form the biologically active form of vitaminD1, 25(OH)2D, 1,25(OH)2D may be responsible for regulating up to 200 genes which may facilitate many of the health benefits 2 . SourcesVitamin D perhaps the one of the vitamin that gets synthesized in the body in the skin with the help of sunlight. Vitamin D 3 is found in animal food e.g., fatty fish (e.g., mackerel, salmon and tuna), cod liver oil, milk. Vitamin D 2 is found in vegetal sources like sun-exposed yeast and mushrooms Causes of Vitamin D Deficiency 2• Inadequate exposure to sunlight -as major source of vitamin D is exposure to natural sunlight.• Skin tone-Dark skin people are more prone for deficiency than white tone as dark skin provide natural sun protection.• Use of sunscreens-reduce...