Vitamin B12, also called cobalamin, is important to good health. It helps maintain healthy nerve cells and red blood cells, and is also needed to make DNA, the genetic material in all cells . Vitamin B12 is bound to the protein in food. Hydrochloric acid in the stomach releases B12 from protein during digestion. Once released, B12 combines with a substance called intrinsic factor (IF) before it is absorbed into the bloodstream. Good sources include meat, particularly liver, salmon, cod, milk, cheese, eggs, yeast extract, and some fortified breakfast cereals.