The B group vitamins are water-soluble and not adequately stored in the body, so needing to be replenished daily to support many body functions. Deficiencies of one or more of the B vitamins can easily occur, particularly at times of stress, fasting and weight-loss, or with diets high in refined and processed food, sugar or alcohol. Deficiency signs may include fatigue, irritability, nervous tension, low mood, insomnia, poor appetite, sore mouth, and cracks at the corners of the mouth. B vitamins help to provide energy by converting carbohydrates to glucose. The normal functioning of the nervous system is dependent on the B complex vitamins. They are often helpful in balancing and conserving energy in individuals who are stressed and tired.