Carbohydrates are necessary for achieving optimal health, and are found in four of the major food groups: whole grains, fruit, vegetables, and dairy products. These are your body and brain's main source of fuel. Carbohydrates are also needed to maintain proper function of the central nervous system, muscles, and metabolism of fat and protein. Today, we find carbohydrates in many forms, making it difficult to distinguish which ones are truly beneficial for us. All carbohydrates break down into sugar in your blood, which causes your pancreas to release insulin that transports sugar to your cells for energy. However, the rate at which food breaks down into sugar determines if your energy levels are going to be stable or climb quickly then crash. Fiber found in carbohydrates slows digestion and helps keep energy levels and hunger in check.