Jim Kraft, age 16, of Montgomery, Ala., for his question:

WHAT CAUSES RICKETS?

Rickets is a childhood disease that is most often caused by a lack of vitamin D. Fortunately, it isn't one of the diseases that we frequently see. It has become very uncommon since we have learned how to eat the right foods.

If a child develops rickets when very young, he or she may have either a bent spine or curved legs. Sometimes the ribs also become bent and the skull bones stay soft.

Not enough calcium is deposited at the growing ends of bones to make them strong in the case of a child stricken with rickets. This growing strip of bone becomes broad and irregular instead of sharp and narrow.

Vitamin D helps calcium and phosphorus get through the wall of the intestine into the blood stream. These minerals form part of the strong framework of the skeleton. Vitamin D can be made by the body when exposed to sunlight and can also be found in fish oils. It is often added to milk.