In general, the body best uses nutrients from foods. Food supplies other nutrients and fiber not found in pills. Some people may benefit from a vitamin pill due to an increased need. Vitamins alone do not provide energy. Energy comes from calories.
Calories come from carbohydrates, protein and fat.
However, vitamins do help the body use energy through the breakdown of these nutrients. Whether natural or man-made, a vitamin is used by your body in the same way. In other words, your body cannot tell the difference. Most people in need of a vitamin pill should choose a multi-vitamin with amounts no greater than the Recommended Dietary Allowances. Experts frequently discourage people from taking single vitamins because they are often in excess of the recommended amount.