Which factors can lead to B12 deficiency?

A deficiency in vitamin B12 can occur due to a variety of factors, but intrinsic factor deficiency is a primary reason. Intrinsic factor is a protein secreted by the stomach that is essential for the absorption of vitamin B12 in the small intestine. When there is a deficiency of intrinsic factor, which can happen in conditions like pernicious anemia, the body cannot effectively absorb vitamin B12 from the foods consumed. This leads to a significant decrease in the availability of this crucial vitamin, which is vital for processes such as red blood cell formation, DNA synthesis, and neurological function.

The other options, while they may relate to overall diet or health, do not directly cause a B12 deficiency. High consumption of dairy would actually provide a good source of B12, excessive intake of green vegetables may lead to other nutritional imbalances but not specifically to B12 deficiency, and smoking can have a myriad of health effects, but it isn’t recognized as a direct cause of B12 deficiency. Hence, intrinsic factor deficiency is a definitive cause of B12 malabsorption and deficiency.