The advice about supplements can get as finicky as the mineral itself. Calcium isn't easily absorbed in large amounts, so it's best to break up your daily intake into two to three doses and to take it with meals, says Heaney. For the calcium to reach your bones, you need to make sure you're getting 200 international units (IU) of vitamin D a day if you are 50 or younger; 400 IU, ages 51 to 69; 600 IU, 70 and older. Your body probably produces enough of the vitamin if you simply step out into the sunlight every day. But you may need to take a D supplement if you're supervigilant about sunscreen or if you're African-American, since melanin acts as a shield. You may have heard that supplements with calcium citrate are absorbed more easily than the calcium carbonate found in antacids, but Heaney says the evidence for both is equally strong. And if you can't be bothered with rules, just down your daily quotient all at once. It's better than not taking any at all.
"That's my worst fear," says the NORA study's Siris. "A woman in her 30s or 40s finds out she has low bone density and her doctor puts her on expensive drugs she doesn't need. It's incorrect for a healthy premenopausal woman to be on Fosamax." Evista, a third drug approved to treat osteopenia in postmenopausal women, is a Selective Estrogen Receptor Modulator, or SERM, which acts like estrogen in some parts of the body but not others. Though Evista is known to slow bone loss in postmenopausal women, it has never been studied for this purpose in younger women. And last November, the first drug that actually stimulates bone growth, Forteo, was approved by the FDA, but again only for women who've been through menopause (it involves a daily injection). None of these drugs has been studied for long-term safety.
Medication is an option for postmenopausal women with osteopenia, although even then, there's no need to rush into it. No one goes from osteopenia to osteoporosis in a year. "If your bone density is low, you might decide you want to get on one of those drugs, and that's a reasonable choice. Or you might wait and get retested in a year," says Siris. The good news is that the osteoporosis drugs have dramatically helped women who already have the disease, reducing their fracture risk by as much as half.
Whenever you do get tested, try not to panic about the results. It's normal to be worried about your bones if your mother has osteoporosis or if you are a slender white woman who hates milk and loves pinot noir. And it's right to want to take charge of your health. "But the thing to remember," says Siris, "is that if you have osteopenia, it doesn't mean your bones are going to fall apart overnight. And there's a lot you can do to keep them strong right now."