Vitamins are complex chemical substances    (find) in many foods. The human body needs them for health and    (grow). The body makes some vitamins, but usually in amounts too small to meet its needs.  vitamins are not made in the body. These must ___(supply). No one knows     (exact) how all vitamins work. Doctors do know that vitamins have very special uses.   , One vitamin cannot take the place of another. The steady absence of one vitamin causes a deficiency disease. Rickets, scurvy, and pellagra are examples___ deficiency diseases.
It is best to get vitamins   eating the foods in which they occur. There are also pills that contain a single vitamin __a combination of vitamins. People should ask their doctors___they take any vitamin pills.