Intrinsic factor is a protein that plays a central role in absorbing a specific nutrient. This substance is necessary for the proper absorption of vitamin B12 from the food we consume. Without intrinsic factor, the body cannot effectively utilize dietary vitamin B12.
Where Intrinsic Factor is Made
Intrinsic factor is produced by specialized cells located within the stomach lining. These cells are called parietal cells. Parietal cells are primarily found in the gastric glands, specifically within the fundus and body regions of the stomach. Once produced, intrinsic factor is secreted into the gastric juice, allowing it to mix with ingested food.
How Intrinsic Factor Works
When vitamin B12 is released from food in the stomach, it binds with intrinsic factor. This newly formed intrinsic factor-B12 complex then travels through the digestive tract. The complex protects vitamin B12 from degradation by the acidic environment and digestive enzymes encountered in the stomach and small intestine.
This protected complex eventually reaches the terminal ileum, which is the final section of the small intestine. Here, specialized receptors on the cells lining the ileum recognize and bind to the intrinsic factor-B12 complex. This binding triggers the absorption of the entire complex into the intestinal cells. Inside these cells, vitamin B12 is released from intrinsic factor and subsequently transported into the bloodstream, where it can be utilized by the body.
When Intrinsic Factor is Lacking
A deficiency in intrinsic factor significantly impairs the body’s ability to absorb vitamin B12, leading to a condition known as vitamin B12 deficiency. This deficiency can result in various health issues, including a type of anemia called pernicious anemia. Pernicious anemia occurs because vitamin B12 is essential for the proper formation and maturation of red blood cells. Without sufficient intrinsic factor, red blood cells do not form correctly, leading to anemia.
Common causes for a lack of intrinsic factor include autoimmune conditions, where the body’s immune system mistakenly attacks and destroys the parietal cells that produce intrinsic factor or the intrinsic factor itself. Gastric surgeries, such as gastric bypass or removal of part of the stomach, can also reduce intrinsic factor production by eliminating parietal cells. Additionally, chronic gastritis, an inflammation of the stomach lining, can weaken the stomach and lead to diminished intrinsic factor production. Symptoms of B12 deficiency due to intrinsic factor issues can range from fatigue and paleness to neurological problems like confusion, memory loss, and nerve damage.