Your digestive system breaks down the complex carbohydrates, fats, and proteins (macronutrients) from the foods we eat into simpler substances that can be used by the body. Digestion begins in the mouth and includes multiple other organs, including the esophagus, small intestine, pancreas, liver, and large intestine. Undigested and unabsorbed nutrients become waste, which is passed out of our bodies. Food is the fuel that can help give us the energy to function. “Carbohydrates become glucose, giving our brain and muscles energy,” says Erica Hornung, RD, nutritionist, UPMC Nutrition Services. “Fats help to store energy, protect our vital organs, and allow certain vitamins to be absorbed. Finally, proteins are the building blocks of all cells in the body, they help to boost your immune system, increase your metabolism, and keep you feeling full.” In addition to these three macronutrients, the micronutrients in vitamins and minerals also provide the necessary fuel for our body. For example, some of the B vitamins help with nerve function, vision, energy metabolism, and the making of new blood cells. Therefore, it’s important to consume a wide variety of foods — doing so helps your body work efficiently.