Moms have been telling their children to eat their vegetables for generations, yet new evidence continues to emerge about the important role these foods play in the body's immune health.

For example, a recent study showed that mice that eat few green leafy vegetables have fewer cells that line the inner organs of the body and serve as the first line of defense against infection. The study revealed that vegetables contain a chemical that signals these protective immune cells to function properly.

"It is still surprising to me," said Marc Veldhoen, who led the investigation. "After feeding otherwise healthy mice a vegetable-poor diet for two to three weeks, I was amazed to see 70 to 80 percent of these protective cells disappeared."

Numerous studies in the past have shown that a diet rich in fruits and vegetables is one the most important keys to maintaining strong immune health. These foods contain a number of important vitamins and minerals that fuel the body's protective ability and keep things function at peak levels.