Bone Builders

Unearthed skeletons from ancient times testify to the durability of bone long after other bodily tissue turns to dust. Living bone in the body, however, can lose mineral and fracture easily if neglected -- a disorder called osteoporosis, or porous bones. One in two women and one in eight men over 50 suffer such fractures, including sometimes life-threatening hip fractures.

But during your preteen and teenage years, you can reduce your risk of fractured bones later in life with calcium-rich foods and physical activity.

Bone Behavior

Your body's 206 living bones continually undergo a buildup, breakdown process called remodeling.

The body starts to form most of its bone mass before puberty, the beginning of sexual development, building 75 to 85 percent of the skeleton during adolescence. Women reach their peak bone mass by around age 25 to 30, while men build bone until about age 30 to 35. The amount of peak bone mass you reach depends largely on your genes. Then gradually, with age, the breakdown outpaces the buildup, and in late middle age bone density lessens when needed calcium is withdrawn from bone for such tasks as blood clotting and muscle contractions, including beating by the heart.

"You can't do anything about the genes you're dealt," says Mona Calvo, Ph.D., a calcium expert for the Food and Drug Administration. "As a teenager, though, you can make the most of things you do control that can build your bones and help reduce the risk of fractures when you are older."

Supporting the skeleton with healthful habits now so it can support you later in life is especially important if you have an increased risk of osteoporosis -- for example, if you're female or have a thin, small-boned frame. These habits are proper diet, exercise, and avoiding bone risks -- lifestyle choices that are bad for bone, like smoking.

Eat Your Way to Strong Bones

The main mineral in bones is calcium, one of whose functions is to add strength and stiffness to bones, which they need to support the body. To lengthen long bones during growth, the body builds a scaffold of protein and fills this in with calcium-rich mineral. From the time you're 11 until you're 24, you need about 1,200 milligrams (mg) of calcium each day.

Adolescent bodies are tailor-made to "bone up" on calcium. Calvo says that with the start of puberty, "your body is at a higher capacity to absorb and retain calcium."

Bone also needs vitamin D, to move calcium from the intestine to the bloodstream and into bone. You can get vitamin D from short, normal day-to-day exposure of your arms and legs to sun and from foods fortified with the vitamin. Also needed are vitamin A, vitamin C, magnesium and zinc, as well as protein for the growing bone scaffold.