Drinking 'this' hastily because it's hot could lead to a troublesome storm of diarrhea.

Seoul issued its first heatwave warning of the summer. The Korea Meteorological Administration issued a heatwave warning across Seoul and various inland areas at 10 a.m. on the 19th. On such hot days, many people drink cold water rapidly to cool down, but this can be a major cause of diarrhea. Here’s why.

Suddenly drinking cold water can cause gastrointestinal problems such as abdominal pain, vomiting, and diarrhea. The normal functioning of digestive enzymes occurs most smoothly at 35-40°C. Drinking too much cold water can lower the temperature of the digestive organs, which may affect digestive function. If less digested food remains in the small intestine for a long time, diarrhea can occur due to osmotic phenomena. Especially in patients with diffuse esophageal spasm, cold water can induce changes in gastrointestinal motility. Diffuse esophageal spasm is a condition where the esophageal muscle wall contracts abnormally due to reflux of acidic stomach contents, causing pain and difficulty swallowing. Patients with sensitive irritable bowel syndrome also should avoid cold liquids like cold water.

Especially, drinking cold water after exercise increases the risk of indigestion, abdominal pain, or diarrhea. Immediately after exercise, blood is prioritized to the muscles, and blood flow to the digestive organs decreases, causing gastrointestinal function to decline compared to usual. Drinking cold water in this state can stimulate the stomach and impair its function. The body expends energy to warm the cold water to a temperature similar to body temperature, which also reduces the energy available for digestion. Additionally, it can cause muscle fatigue to accumulate. To recover from exercise fatigue, metabolic waste products accumulated in the muscles need to be expelled quickly. However, drinking cold water immediately after exercise causes blood vessels to constrict, which may hinder the smooth removal of metabolic waste through the bloodstream. Drinking cold water can also temporarily stiffen the muscles involved in breathing, delaying fatigue recovery.

Therefore, lukewarm water around 30 degrees Celsius, slightly cooler than body temperature, is the best to drink. It is absorbed quickly by the body and does not burden the stomach. When drinking water, do so slowly.