Supplements of vitamin B12 are often recommended for people who consume few animal products in their diet (such as vegetarians or vegans), because the vitamin is found naturally only in foods from animal sources, including meat, poultry, fish, eggs and dairy products.nfortunately, production of this factor decreases with age. Crystalline B12 in supplements does not require this intrinsic factor for absorption. Therefore, you should take B12 as a supplement, and you won't be reliant on the presence of intrinsic factor.