Evidence check: B12 in the context of gut health

The provided context does not contain direct evidence linking vitamin B12 to gut health. Generally, B12 absorption requires adequate stomach acid, intrinsic factor, and a functional ileum. Gut health issues such as SIBO, atrophic gastritis, or inflammatory bowel disease can impair B12 status. Consumer tests often measure serum B12, which may not reflect cellular levels. Based on the given context, evidence is insufficient to draw specific conclusions. Clinical assessment (e.g., holotranscobalamin, methylmalonic acid) is recommended if deficiency is suspected.