Vitamin D can be considered either a vitamin or a hormone. The active from of vitamin D is like a hormone because it is made in one part of the body and regulates activities in other parts.
Vitamin D is essential for the absorption of calcium and phosphorus from the digestive tract and deposition in the bones.
By promoting calcium absorption, vitamin D helps to form and maintain strong bones. When the dietary calcium is not sufficient to satisfy the body’s requirement, then vitamin D mobilizes calcium stores from the skeleton.
It acts in the concert with two others hormones: parathyroid hormone (PTH) from the parathyroid glands and calcitonin from the thyroid glands.
It is also important for regulating cell differentiation and growth. It modulates the transcription of cell cycle proteins, which decrease cell proliferation and increase cell differentiation of a number of specialized cells of the body – osteoclastic precursors, enterocytes, keratinocytes.
It may suggested that vitamin D protective against colorectal cancer.
Vitamin D also has a role in modulating immune defense mechanisms. The receptor is found in significant concentrations in the T-lymphocyte. It has been suggested that by providing vitamin D to infants may prevent the development of type 1 diabetes.
Vitamin D is formed from a substance present in our skin, called 7-dehydrocholestrol when exposed to sunlight. This substance will be converted to cholecalciferol which then enters the bloodstream and travels to the liver.
It is a fat-soluble steroid hormone precursor that contributes to the maintenance of normal levels of calcium and phosphorus in the bloodstream, which in turn needed for the normal mineralization of bone, muscle contraction, nerve conduction and general cellular functions in all cells of the body.
Functions of Vitamin D
