It can help if you're lacking in certain nutrients. The body acquires energy through calories—and although vitamins and minerals don't contain any calories, they do play a key role in energy production. The B vitamins—such as the folate in asparagus and the riboflavin in milk—help release energy from foods for the body to use, so skimping on those can make you sluggish. You can also feel tired and weak if you're iron deficient, because iron helps bring oxygen to cells, where it's used to create energy. Women are more prone to having iron-poor blood, thanks to losses through menstruation and lower intakes of iron-rich foods such as red meat. "If you can undo these deficiencies, through diet or a supplement, you'll definitely feel perkier," says Kulik. But before you load up, keep in mind that exceeding the recommended amount of any vitamin or mineral won't lift your energy level to greater heights.