Vitamin D Deficiency Health Article

Definition

Vitamin D deficiency exists when the concentration of 25-hydroxy-vitamin D (25-OH-D) in the blood serum occurs at 12 nanograms/milliliter (ng/ml) or less. This is one-half to one-fourth the amount normally present. When vitamin D deficiency continues for many months in growing children, the disease commonly referred to as rickets occurs.

Description

Vitamin D is a fat-soluble vitamin, meaning it can be dissolved in fat. While some vitamin D is supplied by the diet, most of it is made in the body. To make vitamin D, cholesterol, a substance widely distributed in animal tissues, the yolk of eggs, and various oils and fats, is necessary. Once cholesterol enters the body, a slight alteration in the cholesterol molecule occurs, with one change taking place in the skin. This alteration requires ultraviolet light, a component of sunlight. Vitamin D deficiency and rickets tend to occur in children who do not get enough sunlight and who do not eat foods that are rich in vitamin D.

Once consumed or made in the body, vitamin D is further altered to produce a substance called 1,25-dihydroxy-vitamin D (1,25-diOH-D). The conversion of vitamin D to 1,25-diOH-D occurs in the liver and kidney. The role of 1,25-diOH-D in the body is to keep the concentration of calcium at a constant level in the bloodstream. Maintaining calcium at a constant level is absolutely required for human life, since dissolved calcium is required for nerves and muscles to work. One of the ways in which 1,25-diOH-D accomplishes this is by stimulating the absorption of dietary calcium by the intestines.

The sequence of events that can lead to vitamin D deficiency and later to bone disease, is as follows: a lack of vitamin D in the body creates an inability to manufacture 1,25-diOH-D. This results in decreased absorption of dietary calcium and an increased loss of calcium in the feces. When this happens, the bones are affected. Vitamin D deficiency results in a lack of bone mineralization (calcification) in growing children.