Vitamin B12 is involved in energy production in your body. It may improve your energy level if you are deficient in this vitamin. It keeps our eyes healthy as we age and prevents age-related macular degeneration. Vitamin B12 is needed for the production of serotonin, a chemical responsible for regulating mood. Vitamin B12 can help improve mood in people with an existing deficiency. Healthy vitamin B12 levels are important for your hair, skin and nails