Pills might seem like an easy fix, but food provides an abundance of nutrients, as well as fiber, that pills lack, says Mary Ryan, a registered dietitian in Jackson Hole, Wyoming.

These nutrients are what keep your body functioning at its best — building strong bones; improving brainpower, mood, and memory; and possibly helping the immune system ward off ailments both small (a cold) and large (cancer).

"Vitamins should be used only as supplements to the diet, not substitutes for healthy food," says Jeffrey Blumberg, Ph.D., director of the antioxidant research lab at Tufts University, in Boston.

While there are hundreds of nutrients, the following information explains the ones you need to consume every day, what they do, and how to get them from your diet.