Plant foods have no vitamin B12 unless they are fortified. You can get recommended amounts of vitamin B12 by eating a variety of foods including the following: 1  Beef liver and clams, which are the best sources of vitamin B12. 2  Fish, meat, poultry, eggs, milk, and other dairy products, which also contain vitamin B12.itamin B12 is a nutrient that helps keep the body's nerve and blood cells healthy and helps make DNA, the genetic material in all cells. Vitamin B12 also helps prevent a type of anemia called megaloblastic anemia that makes people tired and weak.