Vitamins are complex chemical substances found in many foods. The human body needs them for health and growth. The body makes some vitamins, but usually in amounts too small to meet its needs. Other vitamins are not made in the body. These must be supplied. No one knows exactly how all vitamins work. Doctors do know that vitamins have very special uses. One vitamin therefore cannot take the place of another. The steady absence of one vitamin in an otherwise complete diet causes a deficiency disease. Rickets, scurvy, and pellagra are examples of deficiency diseases.  It is best to obtain vitamins by eating the foods in which they occur. There are also pills that contain a single vitamin or a combination of vitamins people should consult their doctors before they take any vitamin pills. Scientists have discovered about 25 vitamins and their different forms that are very important to human beings and other forms of life. Experts believe that there are many more vitamins to be discovered. There are two basic groups of vitamins. One group of vitamins dissolves in fat and is therefore called the "fat-soluble" group. Vitamins A, D, E and K are in this group. The other group is known as "water-soluble" vitamins. These vitamins, understandably, dissolve in water. Among this group are Vitamin C and the B group of vitamins. Vitamin A aids the building and growth of body cells. This vitamin is therefore vital for the growth of children and for good development of babies before birth. Vitamin A is also important for good vision at night. Vitamin B1 is also called thiamine. This vitamin prevents and cures disease. Vitamin B2, called riboflavin, is needed for growth, healthy skin, and for the eyes. Vitamin C, or ascorbic acid, prevents and cures scurvy. Vitamin D is a group of 10 vitamins that prevents rickets. Scientist believe that Vitamin D3 forms in the skin when the body is exposed to sunlight. Because of this, it is called the "sunshine vitamin". A lack of Vitamin D may lead to bone damage; too much may cause kidney disease.   All of the functions of Vitamin E, also called tocopherol, are not known. It is necessary for reproduction in animals. Vitamin K is necessary for making the blood clot. The more that is learned about vitamins, the more it is realized how these chemical substances play a part in all aspects of human activity. What is important for good sight at night?
Vitamin A Vitamin B1 Vitamin B2 Vitamin D