This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorders of Gastrointestinal System Including Diarrhea, Subject name: Pediatrics
All are true regarding osmotic diarrhea EXCEPT: 
Select and explain. 
A. Due to highly osmotic substances in lumen, B. Fasting may improve symptoms, C. Stool reducing substances are present, D. Can be mediated by bacterial toxins
D: Can be mediated by bacterial toxins
Answer: D: Can be mediated by bacterial toxins 
Explanation: Osmotic diarrhea is caused by nonabsorbed nutrients in the intestinal lumen as a result of one or more of the following mechanisms: (1) intestinal damage (e.g., enteric infection); (2) reduced absorptive surface area (e.g., active celiac disease); (3) defective digestive enzyme or nutrient carrier (e.g., lactase deficiency); (4) decreased intestinal transit time (e.g., functional diarrhea); and (5) nutrient overload, exceeding the digestive capacity (e.g., overfeeding, sorbitol in fruit juice). Whatever the mechanism, the osmotic force generated by nonabsorbed solutes drives water into the intestinal lumen. A very common example of osmotic diarrhea is lactose intolerance. Lactose, if not absorbed in the small intestine, reaches the colon, where it is fermented to sho-chain organic acids, releasing hydrogen that is detected in the lactose breath test, and generating an osmotic overload. Another risk for chronic osmotic diarrhea often noted in patients with diarrhea-associated irritable bowel syndrome are foods containing FODMAPs (fermentable oligo- di-monosaccharides and polyols).