Why is sugar added to ORS?
**Core Concept**
The addition of sugar to Oral Rehydration Solution (ORS) is a deliberate design element aimed at providing a readily available source of free energy for the small intestine to absorb electrolytes and water. This is critical in the treatment of dehydration caused by diarrhea, where the gut's ability to absorb electrolytes is compromised.
**Why the Correct Answer is Right**
The presence of sugar in ORS facilitates the absorption of glucose and sodium ions in the small intestine through a sodium-glucose cotransporter (SGLT-1). This mechanism is essential for the effective absorption of electrolytes and water in the gut. The addition of sugar helps to drive the uptake of sodium ions, which in turn enhances the absorption of water and other electrolytes. The sodium-glucose cotransporter works by binding to both sodium and glucose molecules, allowing them to be transported across the intestinal epithelium in a coupled manner.
**Why Each Wrong Option is Incorrect**
**Option A:** There is no evidence to suggest that sugar is added to ORS to provide a source of calories. While sugar does contribute some calories, this is not the primary reason for its inclusion in ORS.
**Option B:** The addition of sugar to ORS does not stimulate gastric emptying. In fact, the presence of glucose in the intestine can slow gastric emptying, allowing for a more gradual absorption of electrolytes and water.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the addition of sugar to ORS is a deliberate design element aimed at facilitating the absorption of electrolytes and water in the small intestine. This is a critical concept in the treatment of dehydration caused by diarrhea, and students should be familiar with the mechanism of sodium-glucose cotransport in the small intestine.
**Correct Answer:** C.