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Sunlight activates the metabolism of vitamin D in the body. Sunlight interacts with chemicals naturally present in the human skin in order to produce the Vitamins. The absolute best source of Vitamin D in the diet can be obtained through whole, fortified milk. Sunlight causes the skin to make activated vitamin D. People also get vitamin D from certain foods and vitamin D supplements.
Vitamin D is included in most multivitamins, usually in strengths from 50 IU to 1,000 IU as softgels, capsules, tablets, and liquids. Recommendations are: 5 micrograms (200 IU or International Units) daily for all individuals (males, female, pregnant/lactating women) under the age of 50 years-old. Vitamin D is not abundant in our usual food choices, so we get most of the vitamin from sun exposure and multivitamins. The problem is that the sun is not a reliable source for everyone.
Vitamin D is essential for promoting calcium absorption in the gut and maintaining adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and prevent hypocalcemic tetany. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts.
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.
Exposure to sunlight in spring, summer and autumn makes up for any shortfall in dietary vitamin D and even short exposure to sunlight during these times is adequate, although there may be problems in winter months in some climates. Babies under 12 months have stores of vitamin D which they accumulate while in the womb.
Calcium can be adjusted within the ranges suggested. Calcium controls innumerable processes in the human body including responses in muscles, bones and glands. Calcium ? and its careful equilibrium ? plays a crucial role in many functions. For example, calcium is necessary for blood vessel constriction and relaxation, blood clotting, nerve function, and hormone secretion (for example, insulin).
Vitamin D is necessary for healthy bones, and it seems for many other organs. The body absorbs calcium and phosphorus in the gut much better with assistance of vitamin D.
Vitamin D is well stored in the body and released gradually over many weeks. Neither calcitriol nor calcidiol with their short half-lives are suitable. Vitamin D is an important nutrient for your health. It is a fat-soluble vitamin that helps your body absorb calcium and build strong bones.
Vitamin D is formed naturally by the body after exposure to sunlight. Fifteen minutes in the sun a few times a week without sunscreen is plenty for many people to manufacture and store all of the vitamin D they need.
Vitamin D's importance in maintaining strong, healthy bones through its interaction with the essential mineral, calcium, is well known. But the vitamin is also vital for the health of the nervous and immune systems, in regulating insulin levels and blood pressure, and even as a possible protector against certain common cancers.
The best known and most serious disease associated with vitamin D deficiency is rickets, which arises when the deficiency causes blood calcium levels to fall too low, and the body to respond by stripping the bones of calcium leading to loss of bone density and malformation.
Interestingly, studies have shown that the geographical pattern of the incidence of rickets is very similar to those for both breast and colon cancer, suggesting a possible (though not fully understood) link between vitamin D deficiency and these diseases. One 5 year study which grouped 120,000 people by levels of vitamin D intake reported that men in the highest intake group had a 29% lower incidence of colon cancer than those in the lowest intake group and similar results have been observed in breast cancer research. Relatively high blood levels of active form vitamin D have also been associated with a lower risk of pre-cancerous growths (polyps) in the colon whereas lower levels of vitamin in the blood have been associated with an increased risk of prostate cancer.
Vitamin D is known to be essential for a healthy immune system and has been shown to be particularly important in helping prevent auto-immune diseases