A daily B-12 supplement provides increased vitality and improved brain function for individuals who are deficient in this important vitamin. The brain, nerves, blood cells and other body parts require this essential nutrient to function properly, according to WebMD.
Vitamin B-12 is obtained naturally from animal protein and is also added to many other food products, such as breakfast cereals. Most people attain sufficient quantities from their daily diet, but vegetarians, people over 50 and those with other health challenges may need to supplement their diet, says the National Institutes of Health.
An individual's B-12 level is found through blood testing. Nutrition experts vary on the necessary required dosage, but they agree that less than 200 picogram/milliliter constitutes a deficiency, reports Today's Dietitian.