Vitamin B12 in meat and dairy products.

Vitamin B12 is synthesized exclusively by microorganisms; therefore, humans must absorb it from food. Excellent sources of B12 are foods of ruminant origin, so dairy and meat products play an important role in efforts to meet the official daily B12 intake recommendation of 3.0 μg. Concentrations of the vitamin vary within foods of ruminant origin, with the highest concentrations found in offal such as liver and kidney. In comparison, dairy products have much lower quantities of the vitamin. In bovine milk, the B12 concentration is stable with regard to breed, feed, season, and stage of lactation, but in ruminant meat, the amount of B12 can vary based on the feeding and husbandry of the animal as well as the cut of meat chosen and its preparation. Processing of ruminant food, including thermal treatment, usually diminishes the vitamin B12 concentration. This review summarizes the vitamin B12 content of foods and discusses the impact of food processing on vitamin content. The contribution of ruminant food sources to B12 intake is specifically evaluated, with its bioavailability taken into account.