Adequate intake of calcium is key to preventing osteoporosis, even in your 30s.
Pop calcium twice a day. The average woman consumes about 600mg of calcium from food in a day—that's only half the recommended daily allowance for thirtysomethings of 1,200mg. Therefore, taking additional calcium is almost always necessary. But since your intestines can digest only 300 to 500mg of calcium at a time, it's better to take one calcium supplement twice a day.
Order salmon. Strive to eat this fish at least twice a week. While salmon's calcium punch benefits your skeleton, it is also rich in omega-3 fatty acids, which Swedish researchers have recently linked to higher bone-mineral density. What's known for sure is that omega-3s improve mood, contribute to better heart and breast health, and increase energy levels. "So, if nothing else, you'll have the get-up-and-go to head to the gym—thus improving your bone health," says Dr. Thacker.
Take D alone. Chances are you don't get enough vitamin D from sunlight. "This is especially the case now that women slather on moisturizer with SPF to prevent wrinkles and skin cancer," says Dr. Thacker. Your body needs adequate amounts of vitamin D to absorb calcium.
Even though some foods are fortified with D, and a few, such as fish and egg yolks, contain this vitamin naturally, 40% to 70% of Americans are still deficient and need a supplement. Dr. Thacker recommends taking D on its own. Why? Taking A and D together, as they're often sold, can result in too much A, which puts women at increased risk for hip fractures. This is because retinol, the active form of A, may weaken bones.