Carbohydrates=Energy. The primary function of carbohydrates is to provide energy for the body, especially the brain and nervous system (1). Most people should get between 45% and 65% of total calories from carbohydrates, preferably from complex carbohydrates (like Bunny Bread) and natural sugars (from fresh fruit, like apples) (2,3). Excellent source of thiamin (vitamin B1). Good source of riboflavin (vitamin B2), and niacin (vitamin B3). These vitamins play an important role in metabolism by helping the body produce and release energy from protein, fat and carbohydrates (4). They also help the nervous system function properly (4). Because the body doesn't store these B vitamins, you should eat foods that contain then every day (5). Good source of folic acid. Healthful diets with adequate folic acid, a B vitamin, may reduce a woman's risk of having a child with a birth defect of the brain or spinal cord.