Which of the following is a potential cause of vitamin B12 deficiency?

Pernicious anemia is a specific condition that leads to vitamin B12 deficiency due to an inability to absorb the vitamin in the intestines. This occurs because of an autoimmune attack on the gastric parietal cells, which produce intrinsic factor, a protein essential for the absorption of vitamin B12 in the small intestine. Without intrinsic factor, even if dietary intake of vitamin B12 is adequate, the body cannot effectively absorb this vital nutrient, leading to deficiency. Symptoms of vitamin B12 deficiency can include anemia, fatigue, neurological issues, and glossitis, among others.

The other options do not contribute to vitamin B12 deficiency in the same manner. A high fiber diet can be beneficial for overall health and does not directly interfere with the absorption of vitamin B12. A sedentary lifestyle has no direct correlation with vitamin B12 levels, as it primarily affects physical fitness and overall health rather than nutrient absorption. Excessive vitamin D intake does not affect vitamin B12 status; rather, it can lead to hypercalcemia and related issues. Thus, pernicious anemia distinctly stands out as a recognized cause of vitamin B12 deficiency.