Calcium and Osteoporosis: How Much Calcium is Enough?

Drink milk at the dinner table? Some scoff at the habit--but your bones may be better for it.

Calcium is a principal building block of our skeleton, the mineral that keeps our bones from growing brittle and breaking.

"Bones are a living organism, just like the heart," says Edward McPherson, M.D., USC associate professor of orthopaedic surgery. "Bone is not an inert matter. Old bone is reabsorbed back into the body while new bone is made."

But this process reverses by age 35, when the resorption outpaces new bone generation. Bones lose density, a condition that can lead to osteoporosis, or porous bone disease.

"Over time you'll have potholes here and there," McPherson explains. "Every time you lay down to sleep you develop micro-cracks in your bone."

The secret to healthy bones? Get enough calcium and regular exercise, he says.

An adult should consume 1000 mg of calcium daily. The following foods are the richest in calcium: skim milk (302 mg. per cup), tofu (260 mg.) plain, low-fat yogurt (415 mg) or collard greens (357 mg.).

As for exercise, McPherson recommends 30 minutes of daily moderate activity. And exercise isn't just high-impact activities such as contact sports or running. Walking, gardening, playing golf or even dancing are all exercise, especially if done vigorously.

He also recommends that those with a high risk of osteoporosis - thin, fair-skinned people and post-menopausal women - get a baseline measurement of bone density in their late 30s. The full-body scan takes no more than 20 minutes.

"I'm extremely religious on that," McPherson says. "Fractures can be prevented with early detection and management."

So next time your friends laugh at your drinking habits, raise your milk glass proudly aloft and toast to the health of your 206 bones.