In Your 20s

Iron
This mineral is crucial for the body to make oxygen-transporting proteins in the blood (a.k.a. hemoglobin and myoglobin). While most people associate iron with red meat and spinach (Popeye!), there are many other ways to load up (most dried beans and green veggies have it, as well as salmon, tuna, and egg yolks). It may sound cavewoman-esque, but when your body is in full-reproduction mode from a biological standpoint (whether you’re ready or not), your monthly cycle is probably at its, um, best? (Read: heaviest). “It’s important to replenish lost blood,” says Morrison, who suggests having approximately 18 to 27 mg a day (which is also the amount often laced in a multi).

Calcium & Vitamin D
This dynamic duo is no longer just an old-lady staple. “You need to starting getting enough now to ward off osteoporosis and subpar bone health,” says Gans. Of course, calcium is pretty easy to get — grab a yogurt for breakfast or hover over the cheese plate — but Gans says that she finds many of her female clients don’t reach the three servings a day that’s needed — the equivalent of about 600 mg. As for vitamin D, which has gotten more press this year than Lindsay Lohan, there aren’t as many foods to choose from — the only fortified foods include cereal and milk or salmon — and the vitamin is crucial to have so that your body can absorb the calcium. Recently, after much hoopla, the IOM increased its recommendation of D from the archaic 400 units daily dose to 1,000. Gans suggests taking the D with some fat, like after having a salad with olive oil, for better absorption (but more on that later) and to split the calcium dosage (500 and 500), because the whole thing at once can’t be absorbed — take one in the a.m. and the other at lunch, she says.