Ever said, "I wonder where those kids get all that energy?"

According to Lee Berk, associate director at the Center for Neuroimmunology at the Loma Linda School of Medicine, children have a secret energy source, one which is available to any of us.

They laugh. A lot. In fact, Berk notes in this month's Parenting Magazine that children laugh an average of 400 times a day, while adults guffaw only 15 times.

Through years of research, Dr. Berk and his colleagues have discovered that laughter produces NK cells, functions as an analgesic, suppresses the release of cortisol, increases circulatory capacity, and strengthens organs.

In other words, laughter fights infections, raises the body's pain threshold, and strengthens the immune system. It also significantly increases energy.

Want to stay well and energetic this winter? Heard any good jokes?