Multivitamins are a combination of different vitamins normally found in food sources. They are used to provide vitamins that are not taken in through your diet. The primary role of a multivitamin is to fill nutritional gaps and make sure people get their daily allowance of underconsumed nutrients like vitamins A, C, D, E and K, calcium, magnesium, dietary fiber, choline and potassium. Vitamins and minerals are considered essential nutrients—because acting in concert, they perform hundreds of roles in the body. They help shore up bones, heal wounds, and bolster your immune system. They also convert food into energy, and repair cellular damage.