Keeping bones strong

Ounce for ounce, bone bears as much weight as reinforced concrete. However, unlike reinforced concrete, bone is a living tissue. It serves as a repository of minerals for the rest of the body to use, continuously lending them out and replacing them. Bone also gets stronger when "stressed" by physical activity, and can repair itself when injured.

The building and tearing down of bone tissue is called remodeling. This process happens continuously throughout your entire life. At first, your body rebuilds more bone than it demolishes. Typically, a person reaches peak bone mass around the age of 30. Among women, bone mass usually remains steady for the next 20 years or so until the onset of menopause, when bone is lost much more quickly than it is replaced. When bone loss is significant, the result is osteoporosis (which means "porous bone"). Bone loss generally starts later for men — typically in the late 50s — and progresses more slowly than in women. But men can also get osteoporosis.

When you have osteoporosis, you can no longer count on your skeleton to withstand even routine stress. A twist, a bend, an unexpected jolt — all can snap a vulnerable bone.

Two critical factors in minimizing bone loss are diet and exercise.

Osteoporosis and diet

Calcium is the building material for strong bones. Vitamin D helps your intestines absorb calcium into the bloodstream, which delivers it to your bones, muscles, and other body tissues.

According to the National Osteoporosis Foundation (NOF), men and women ages 51 and older should consume 1,200 milligrams (mg) of calcium a day. It's best to get your nutrients from a balanced, nutritious diet. Dairy products provide the most concentrated sources of calcium. But you can also find calcium in tofu, almonds, spinach, kale, broccoli, fortified orange juice, and canned fish that includes soft bones (like sardines and salmon).

In addition, the NOF recommends 800 to 1,000 international units (IU) of vitamin D per day for men and women ages 50 and older. There are only a few good food sources of vitamin D, such as eggs, saltwater fish, and liver. As a result, most people find they need a supplement. Your body will most easily absorb and use the form of vitamin D called cholecalciferol (or vitamin D3), so look for a D3 supplement.

Vitamin K also helps keep bones strong. This vitamin is found in leafy greens and cruciferous vegetables. A cup of fresh raw spinach will deliver more than enough. So will a generous portion of cooked broccoli or Brussels sprouts.

Osteoporosis and exercise

Weight-bearing exercise — movement that forces a part of your body to work against gravity — encourages the bones in that area to shore up their strength. Weight-bearing exercise includes any activity where your body must bear its own weight — for example, tennis or running. However, if you know you have osteoporosis, you'll want to start with gentler activities — such as tai chi or walking — and get your doctor's advice before starting an exercise program.

For more information on staying healthy and active as you get older, buy A Plan for Successful Aging, a Special Health Report from Harvard Medical School.