If you eat a well-balanced, healthy diet, should you take a multivitamin? Most experts agree that it can't hurt and it might help. "No matter how well we try to eat, there are days when we fall far short of the ideal," says registered dietitian Mary Ryan. In those instances, "a multi covers most of the bases," she says. Most multis are packed with all the major vitamins and minerals and can give a little boost to your daily diet. Look for ones with nutrient levels at or close to 100 percent of the RDAs.