What is Vitamin B12? Vitamin B12 (Cobalamin) is a water soluble vitamin & essential nutrient. Vitamin B12 is found in foods of animal origin, including dairy, eggs, meat, poultry, & fish. It is often lacking in a vegetarian diet. What Does Vitamin B12 Do? May help to support a healthy nervous system. Helps to maintain normal homocysteine levels. Helps to maintain healthy energy levels. Supplements a vegetarian diet.