B vitamins are essential to support energy and maintain mental alertness, particularly when experiencing fatigue. B complex is necessary for healthy function of blood, brain, and nerve cells which are vital for sustained energy. B vitamins are water soluble and must be replenished daily for the body to operate at peak energy.
Many studies suggest that levels much higher than the government set RDA may be needed for optimal function. 25-100 mg a day of each B Vitamin (250+ mcg/day for Vitamin B12) is a better recommendation.