Even though bones are made up mostly of calcium, magnesium also plays a huge role in bone health. "Magnesium assists absorption of calcium and vitamin D into the bones," says Dr. Carolyn Dean, medical director of the nonprofit Nutritional Magnesium Association.

"It also stimulates calcitonin, a hormone that helps preserve bone structure and draws calcium out of the blood and soft tissues back into the bones."

Trouble is, most of us don't get enough magnesium from food, Dean says, because today's soil has become depleted of the mineral. "One hundred years ago, there was about 500 mg of magnesium in our daily diet," she says. "Now we are lucky to get 200 mg." To load up on magnesium, Dean recommends kelp, wheat germ, wheat bran, cashews, and almonds. She's also a big fan of supplements. "I feel most people, especially athletes who sweat out a lot of magnesium, should supplement with about 300 mg of magnesium citrate powder, a highly absorbable form," she says.