Where in the body is vitamin B12 primarily absorbed?

Vitamin B12 is primarily absorbed in the terminal ileum of the intestines. This absorption process occurs after vitamin B12 has undergone several critical steps prior to reaching the ileum. First, vitamin B12 is released from food sources in the stomach, aided by gastric acid and digestive enzymes. In addition, intrinsic factor, a protein secreted by parietal cells in the stomach, binds to vitamin B12, forming a complex that is crucial for its absorption.

As this complex moves through the digestive tract, it reaches the terminal ileum, where specific receptors facilitate the uptake of vitamin B12 into the enterocytes. This process is essential for maintaining normal levels of vitamin B12 in the body, which is vital for red blood cell formation, neurological function, and DNA synthesis.

This understanding emphasizes the unique role of the terminal ileum in the absorption of vitamin B12, distinguishing it from other parts of the gastrointestinal tract where various forms of nutrient absorption occur, but not specifically for B12.