What Vitamin D3 Does For Your Body

Vitamin D is a fat-soluble vitamin that is derived from a few food sources, vitamin supplements and sunlight. Vitamin D comes in three forms, all which perform the same functions in the body. Vitamin D3, also called cholecalciferol, is naturally made when ultraviolet rays come in contact with the skin. Vitamin D3 is also found synthetically in supplements.

Vitamin D3 Absorption

Vitamin D3 from the sunlight is only available during the summer months and at midday sun coverage. The National Health Institute lists season, time of day, length of day, cloud cover, smog, skin melanin content, and sunscreen as factors that can impact vitamin D synthesis. Whether vitamin D comes from the sunlight or through the diet, it is converted to a vitamin D metabolite in the blood. Vitamin D under goes two transformations in order to be used by the body; one happens in the liver and one in the kidney.

Calcium Absorption

Vitamin D3 increases calcium absorption in the gastrointestinal tract, and sufficient levels of vitamin D3 are needed for adequate calcium absorption. Vitamin D3 also maintains calcium levels circulating in the body, which is very important for bone and nerve function. Vitamin D3 regulates circulating calcium levels by impacting the kidneys for the amount of calcium that is excreted or put back into the body.

Bone Development

Vitamin D3 influences bone development or bone breakdown. When there in insufficient calcium in the blood, vitamin D3 helps regulate the breakdown of bone to release calcium into the blood. When calcium levels are sufficient, the calcium goes into the bone. Vitamin D3 deficiency causes rickets, a condition where bones are soft, weak and do not develop properly in children. Although rickets is rare in the Western world, low vitamin D3 and calcium can cause osteomalacia or osteoporosis.

Cell Growth

Vitamin D3 plays a role in controlling genes that determine cell growth and proliferation in the body. When cells proliferate uncontrolled, benign or malignant tumors can result. Vitamin D3 limits out-of-control cell proliferation and helps differentiate these cells to something useful for the body.

Other Functions

Vitamin D3 has other functions in the body unrelated to calcium or bone formation; many cells have vitamin D3 receptors. Vitamin D3 may help the immune system by increasing natural immune defenses and inhibiting auto-immune disorders. Vitamin D3 also affects insulin secretion, the neuromuscular system and blood pressure regulation.