Vitamins do not share a common chemistry, but they do share certain characteristics. They are all organic nutrients that are necessary in small amounts for normal body functioning and good health. A well-balanced diet should provide most of the vitamins people need to stay healthy and prevent disease. Vitamin D is the only exception. Supplements can be helpful in some situations, such as pregnancy and certain illnesses. Strict vegetarians may benefit from taking vitamin B12 supplements. Unlike carbohydrates, fats, and proteins, vitamins are not sources of energy. Instead, vitamins are involved in the body's metabolism, cell production, tissue repair, and other vital processes. If you want to know more about, read this book. Find if you are one of the people who need them and why.