Role in the Body
Vitamin D is essential for the absorption and metabolism of calcium and phosphorus from food and for maintaining proper calcium levels in the blood. It is very important for strong bones and teeth, is involved in cell growth, enhances the immune system, regulates blood sugar levels, and is necessary for nerve impulse transmission and muscle contraction.
Vitamin D is found in fortified milk (all milk in the United States is fortified with vitamin D) and fortified cereals, butter, margarine, cheese, fish, and oysters.
In addition, the body can make vitamin D when the skin is exposed to sunlight. Direct sunlight on the face and arms for 10-15 minutes, three times a week is recommended to meet vitamin D requirements.
Who Is at Risk for Deficiency?
You may be at risk for deficiency if you don't get much sunlight, are a strict vegetarian or vegan, are lactose-intolerant, have kidney or liver disease, take certain cholesterol-lowering drugs, corticosteroids, or anticonvulsant drugs, or abuse alcohol. Older folks are also at risk as the skin makes less vitamin D as we age.
Vitamin D may protect against colon cancer, and possibly breast and prostate cancers. Vitamin D can protect against hearing loss by strengthening the small bones of the ear. And in cream form, vitamin D can help relieve the skin disorder, psoriasis.
Large doses of vitamin D over a period of time can be toxic. Vitamin D should not be taken without calcium.