The B vitamins are a family of eight unique vitamins that play several important individual and collective roles in your body. One of their key functions is to support the production of cellular energy from the foods you eat. When you consume a meal, all eight B vitamins are required for the metabolic processes that convert the carbohydrates, proteins and fats that you eat into cellular energy. This cellular energy is used to fuel your body's many chemical reactions. Vitamin C is also required for cellular energy production from the fats that you eat.