A dietary supplement is a manufactured product intended to supplement the diet when taken by mouth as a pill, capsule, tablet, or liquid. A supplement can provide nutrients either extracted from food sources or synthetic, individually or in combination, in order to increase the quantity of their consumption. Dietary supplements come in a variety of forms, including tablets, capsules, gummies, and powders, as well as drinks and energy bars. Popular supplements include vitamins D and B12; minerals like calcium and iron; herbs such as Echinacea and garlic; and products like glucosamine, probiotics, and fish oils. Among supplement users, multivitamins were the most commonly used supplement (71%), followed by omega-3 or fish oil (33%), calcium (32%), vitamin D (32%), and vitamin C (32%). Supplements that increase your calorie or protein intake could help you gain muscle when combined with an appropriate exercise program, typically weight training ( 2 , 32 ). However, for most supplements there is little evidence to suggest that they can increase weight or muscle gain on their own.