• Curb cravings. A multi may make you less hungry when you're dieting, reveals a new Canadian study. Researchers think that it short-circuits the body's natural response to calorie cutting, which is to boost appetite to counter vitamin deficiencies.

• Keep energy up. A good vitamin prevents low iron, which makes you drag during workouts and may also cause hair loss, according to a French study.

• Safeguard your heart. The ingredients in a multi have been linked to a lower heart disease risk. But it's an aid to — not a substitute for — fruits and veggies, which may deliver other disease-fighting compounds.

• Stave off breast cancer.Taking a multi may cancel out the breast cancer risk incurred by drinking alcohol. In a recent study from Boston's Brigham and Women's Hospital, women who had a daily cocktail and took a multi had a lower risk than those who didn't pop the pill. The supplement may correct alcohol-triggered deficits of B vitamins that encourage tumor development.

• Get pregnant. Multi users have a 41 percent lower risk of ovulatory infertility, finds a Harvard School of Public Health study. Folic acid and other B vitamins appear to help promote healthy ovulation.