Figure 2.

Vitamin B₁₂ sources and microbial interactions in meat, eggs, milk, and milk products. Cattle are herbivorous ruminant animals and their stomachs contain various microorganisms including B₁₂-synthesizing bacteria. The synthesized B₁₂ is absorbed in the intestine and stored in the liver and muscles of cattle or secreted into milk. Bovine milk and fermented milk (yogurt and cheese) are major dairy products for humans. Chickens are omnivores and eat both plants and animals that contain considerable amounts of B₁₂. The B₁₂ contents of raw meats are generally higher in cattle than in chicken.