The body uses vitamin B-12 to help produce DNA and maintain nerve and blood cell health, explains the National Institutes of Health. The main use of supplementation is to address a vitamin B-12 deficiency. A bacterial fermentation process creates supplemental vitamin B-12 in the form of cyanocobalamin, notes Precision Nutrition.
Although most individuals in the United States consume adequate amounts of vitamin B-12 in their diets, there are several reasons some people become deficient in the nutrient, states the NIH. People who eat vegetarian or vegan diets often develop a deficiency because the only natural sources of vitamin B-12 are animal foods. Breastfed babies may also become deficient in the vitamin if their mothers do not include animal foods in their diets. Pernicious anemia is another cause of vitamin B-12 deficiency. Patients with this condition do not produce the intrinsic factor that allows for the absorption of the vitamin. Additionally, gastrointestinal surgery, Crohn's disease and celiac disease make individuals more prone to deficiency.
Natural food sources of vitamin B-12 include clams, beef liver, poultry, dairy products and eggs, notes the NIH. Fortified breakfast cereals and nutritional yeasts also contain the vitamin. Vitamin B-12 deficiency symptoms include weight loss, fatigue and constipation.