Vitamins regulate cell functions and help convert the food we eat into energy. Since the first vitamin was identified in the early 1900s, knowledge of their benefits has grown yearly.

Early treatment of vitamin deficiencies resulted in vast improvements in health: English sailors no longer suffered from scurvy, and children going blind from vitamin A deficiency regained their sight.

Nearly 40 percent of U.S. adults take vitamin supplements regularly, spending $2.7 billion last year.

No consensus exists as to which vitamin supplements are best or exact amounts that should be taken. That depends on age, gender, pregnancy, weight, environment, pre-existing health conditions, and even genetics. Over-the-counter vitamins should be fine. Steer clear of supplements advertising “miracle” cures.

The U.S. Committee on Dietary Allowances, Food and Nutrition issues the following recommended daily allowance for vitamins. (RDA amounts listed below are subject to revision.)