Despite increasingly focused marketing — for seniors! for carb watchers! — one daily vitamin suits most. Good, general adult versions work for teenager and Grandpa alike. Choose one that’s both a multivitamin and a multimineral and contains about 100 percent of the minimum daily requirement for the essentials in both categories. “Although most children don’t need multivitamins, you should generally ask your physician,” says Dennis Bier, M.D., director of the Children’s Nutrition Research Center, in Houston. Your doctor can tell you whether a pill with vitamins or certain minerals in much higher levels than the minimum daily requirements might be beneficial for a specific condition (women who are pregnant, lactating, or trying to conceive, for example, require higher doses of folic acid), but stay away from multivitamins with high doses of trendy herbs, many of which haven’t been proved safe in large research studies.

Next, look for the United States Pharmacopeia (USP) seal. Though compliance to USP standards is voluntary, Jeffrey Blumberg, a professor of nutrition science and policy at Tufts University, believes the seal can help validate an unfamiliar brand. Finally, check the expiration date on the bottle. According to Sam Knoll, chief executive officer of Myvitaminguide.com, an online vitamin-information source and shop, “failing to do so is one of the biggest mistakes people make.”