What Does Vitamin D Do?

Child suffering from rickets

Vitamin D is a fat-soluble vitamin and exists in several forms. There are two forms which are important in humans: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Plants synthesize vitamin D2, and vitamin D3 is synthesized by humans in the skin when it is exposed to ultraviolet-B (UVB) rays from sunlight. The liver and kidney help convert vitamin D to its active hormone form.

Vitamin D has the following functions:

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• The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus.

• Vitamin D is absolutely necessary for the growth and development of bones and teeth.

• It is essential for the proper absorption and utilization of calcium and phosphorus in the body; both are important to the health of the skeleton.

• Vitamin D promotes bone mineralization with a number of other vitamins, minerals, and hormones.

There are two diseases that occur with a vitamin D deficiency, namely, osteomalacia and rickets. Osteomalacia is found in adults and results in muscular weakness in addition to weak bones. Rickets is found in children and results in skeletal deformities.

Vitamin D is found in dairy products such as cheese, butter, cream, fortified milk. Other foods containing vitamin D are: fish, oyster, fortified cereal and margarine.

Consuming too much vitamin D can result in a high health risk. It can increase your risk for kidney stones and excess calcium in the blood. High blood calcium can lead to calcium deposits in soft tissues such as the heart and lungs. This can reduce their ability to function. Vitamin D toxicity can cause nausea, vomiting, poor appetite, constipation, weakness, and weight loss. Too much vitamin D mostly occurs from high intakes of vitamin D in supplements.

Exposure to sunlight is an important source of vitamin D. It is still important to routinely use sunscreen whenever sun exposure is longer than 10 to 15 minutes.