Final answer:
If the stomach cannot secrete intrinsic factors, vitamin B12 is not absorbed by the body, risking nutritional deficiency and necessitating alternative forms of supplementation.
Step-by-step explanation:
The stomach plays a crucial role in the absorption of vitamin B12 due to the secretion of a substance called intrinsic factor. This intrinsic factor binds with vitamin B12 and facilitates its absorption in the ileum, which is the last part of the small intestine. If the stomach does not secrete enough intrinsic factors, vitamin B12 cannot be properly absorbed, leading to its deficiency. Without the intrinsic factor, the vitamin B12 present in the diet would pass through the digestive system and be excreted without being absorbed. Therefore, the answer to the student's question is that B12 is not absorbed by the body.