Vitamin D, that is. You'll need it to aid in the absorption of all that calcium you'll be ingesting. Fortunately, your own skin produces vitamin D in response to sunlight. Getting just 10 to 15 minutes of sunlight exposure two to three times week should enable you to meet the vitamin D requirements for most people. Drinking vitamin-D-fortified milk can also boost your intake, but consider with caution a dietary supplement, since too much vitamin D can be toxic.

Exercise has been proven to help prevent osteoporosis, as the pull of the muscles against the bones spurs the building of more bone cells. In particular, weight-bearing activities such as jogging, walking or stair climbing can help build bone strength, as can resistance exercise using free weights, fitness bands or weight machines.

While some drugs may increase your risk of osteoporosis, others have been approved by the U.S. Food and Drug Administration for both the treatment and prevention of the disease:

• Hormone replacement therapy (HRT)
• Alendronate sodium (Fosamax)
• Risedronate sodium (Actonel)
• Raloxifene (Evista)
• Calcitonin (Miacalcin)

Certain medications may increase your risk of osteoporosis:

• Immunosuppressants, including prednisone and other steroids, methotrexate and cyclosporine
• Thyroid drugs
• Anticonvulsants
• Aluminum-containing antacids
• Cholesterol-lowering drugs
• Long-term heparin therapy

While these drugs may increase bone loss, they may also be essential for treating serious conditions. Discuss the pros and cons of your medications with your physician.

If you smoke, here's yet another reason to quit. Smoking has been shown to decrease bone density, increasing your risk of fractures. Furthermore, once bones have been broken, smoking may hinder the healing process, since smokers carry a lower amount of oxygen (essential for healing) in their blood. Female smokers have also been shown to start menopause an average of five years earlier than non-smokers, increasing their risk of osteoporosis.

Don't drink away your dietary efforts! Alcohol can interfere with vitamin D metabolism, which in turn affects your body's absorption of calcium. Excessive alcohol consumption can also affect hormone production, causing irregular menstrual periods in premenopausal women and lowering testosterone levels, both of which increase one's risk of osteoporosis.

Though the National Osteoporosis Foundation recommends a daily calcium intake of 1,000 to 1,200 milligrams for adult men and women, most of us aren't getting enough of this essential nutrient. To boost your intake, add more of these calcium-rich foods to your diet:

• Low-fat dairy products
• Sardines and salmon canned with bones
• Broccoli
• Spinach and other dark green leafy vegetables
• Calcium-fortified products such as orange juice or cereals

The numbers don't lie: Osteoporosis is a national epidemic. Approximately one-third of all postmenopausal women have or are developing the "silent disease," which often develops over many years without evident symptoms. <p>So why should you care?