Vitamin B12 is a water-soluble vitamin that keeps your nerves and red blood cells healthy.  It is responsible for the smooth functioning of several critical body processes.  Strict vegetarians, heavy drinkers and smokers, pregnant and breast-feeding women, and the elderly usually require vitamin B12 supplements.  It is needed to convert carbohydrates into glucose in the body, thus leading to energy production and a decrease in fatigue and lethargy in the body.  It helps in healthy regulation of the nervous system, reducing depression, stress, and brain shrinkage.  B12 helps maintain a healthy digestive system. Vitamin B12 also protects against heart disease by curbing and improving unhealthy cholesterol levels, protecting against stroke, and high blood pressure.  It is essential for healthy skin, hair, and nails.  It helps in cell reproduction and constant renewal of the skin.  Vitamin B12 helps protect against cancers including breast, colon, lung, and prostate cancer.