To answer this question, we must first define the temperature of "hot water". Personally, it is cooled to a temperature suitable for drinking after boiling. In some related clinical studies, the temperature of hot drinks is generally between 55-7 degrees Celsius. (Of course, if anyone can't take it easy and just sip boiling water, that's another matter.). In fact, there are many variables hidden behind "drinking hot water", and there are two most important variables. The first is intake. A French research group found that drinking hot drinks can lead to a sudden rise in the temperature in the esophagus of 6-12 degrees, and the degree of warming is directly proportional to the average intake. This variable is very easy to understand. The heat damage to esophagus caused by drinking hot water with the same temperature as fine products is of course different. (The above article also mentioned the relationship between intake and risk.) Secondly, the intake components, like 65-degree hot water, hot tea or hot coffee, have different additional effects on injury and carcinogenesis due to different chemical components. For example, assuming that high temperature can cause thermal damage to esophageal epithelial cells to a certain extent, the presence of caffeine can enhance the wound healing rate and reduce the inflammatory reaction compared with water, but it will also cause the disorder of DNA repair pathway and cell cycle, and then increase the risk of cancer.

Personally, the biggest reason may be that the heat damage to esophagus and stomach causes inflammatory reaction, which leads to DNA repair, cell cycle and related signal pathways disorder of esophageal epithelial cells or gastric wall cells. The positive correlation between inflammation and gastric cancer/esophageal cancer has long been confirmed. There are also some tumor prevention studies that show that long-term use of non-steroidal anti-inflammatory drugs (NSAID) can significantly reduce the risk of esophageal cancer and gastric cancer. Please correct me if there are any inadequacies in the above reasons, but in order to strictly answer the question of the subject, many other cultural, customs and environmental factors need to be considered. For example, in American restaurants, no matter what season, all meals are iced water, but in China, it is usually hot tea.