Ingestion of osmotically active substance causes osmotic diarrhoea. Which of the following can cause osmotic diarrhea?
**Core Concept**
Osmotic diarrhea is caused by the ingestion of substances that draw water into the intestines through osmosis, leading to a watery stool. This occurs when the concentration of solutes in the gut lumen is higher than in the bloodstream, causing water to move from the bloodstream into the gut to equalize the solute concentration.
**Why the Correct Answer is Right**
The correct answer is a sugar (sorbitol) that is poorly absorbed by the small intestine. Sorbitol is a polyol sugar that is commonly found in sugar-free gum, candy, and diet foods. When ingested, sorbitol is absorbed into the bloodstream but not efficiently by the small intestine, leading to an osmotic gradient across the intestinal epithelium. Water moves into the gut to equalize the solute concentration, resulting in osmotic diarrhea. This is a classic example of an osmotically active substance causing osmotic diarrhea.
**Why Each Wrong Option is Incorrect**
**Option A:** Lactose is a sugar that is poorly absorbed by some individuals, but it is not typically associated with osmotic diarrhea. Instead, lactose malabsorption leads to carbohydrate malabsorption diarrhea.
**Option B:** Fructose is a sugar that can cause gastrointestinal symptoms, but it is not typically associated with osmotic diarrhea. Fructose malabsorption can lead to bloating, gas, and abdominal pain, but it does not typically cause osmotic diarrhea.
**Option C:** Glucose is a sugar that is well-absorbed by the small intestine and is not typically associated with osmotic diarrhea.
**Clinical Pearl / High-Yield Fact**
Remember that osmotic diarrhea is caused by the ingestion of substances that draw water into the intestines through osmosis, leading to a watery stool. Common causes include poorly absorbed sugars like sorbitol, lactulose, and xylitol.
**Correct Answer:** D.