If you often feel tired, run-down, and lacking in energy, you're not alone. Low energy is one of our country's biggest health complaints. Inadequate blood levels of Vitamin B12 can be one of the symptoms related to low energy, mental fatigue, mood changes, sleep difficulties, and even occasional indigestion. Your body relies on the efficient conversion of carbohydrates to glucose – your body’s source of fuel. Vitamin B12 enables your body to convert fatty acids into energy. In addition, it is also needed for proper digestion, food absorption, carbohydrate and fat metabolism. It also helps keep your nervous system healthy by assisting the nerves of your body to function and communicate in an optimal manner. Vitamin B12 also helps to support the female reproductive system. It is also responsible for your circulation and adrenal hormone production -- plus, it helps boost your immunity. Overall, Vitamin B12 is a vital nutrient that your body cannot do without helps you fight vitamin B12 deficiency, increase your energy, enhance your immunity, promote good mood, and support mental alertness. A daily intake of Vitamin B12 supplement is well advised for vegetarians and vegans, as this vitamin is normally lacking in vegetarian diets.