The main causes and risk factors of esophageal cancer are as follows:
(1) Nitrosamine compounds:
Experimental studies have shown that nitrosamine compounds can cause cancer in more than 10 animal species, as well as induce esophageal epithelial cancer in animals and human fetuses. In high-risk areas of esophageal cancer in China, the levels of nitrosamine compounds in pickled vegetables and improperly stored grains are higher compared to low-risk areas. Nitrite and nitrate, which are present in drinking water and food, can be converted into carcinogenic nitrosamines under appropriate conditions, leading to esophageal cancer. Researchers have also found small amounts of nitrosamine compounds in homemade fish sauce, preserved vegetables, dried radish, aged cornmeal, aged rice, and moldy foods in high-risk areas of esophageal cancer in China. Acidic pickled vegetables from Lin County have been found to contain significant amounts of nitrate and nitrite, as well as dimethylnitrosamine, diethylnitrosamine, methylbenzylnitrosamine, and other unknown nitrosamine compounds that can induce animal esophageal cancer.
Research has shown a positive correlation between the intake of nitrosamine compounds from the diet and the incidence of esophageal cancer. Specifically, people from Lin County have a higher intake of nitrosamine compounds compared to individuals from low-risk areas of esophageal cancer, and their intake is approximately 100 times higher than that of people from the United States, United Kingdom, and Germany. Chinese researchers have isolated and identified methylbenzylnitrosamine, a nitrosamine compound that can induce animal esophageal cancer, from the diet of high-risk areas for esophageal cancer. This provides important evidence for the etiology of esophageal cancer. In 95% of the gastric fluid samples from 353 individuals in Lin County, nitrosamine compounds were found, indicating that the synthesis of nitrosamine compounds in the stomach is a major source of nitrosamine compounds in the human body.
(2) Research has demonstrated that Fusarium moniliform (mold) and alternaria alternata, along with their toxins isolated from grain in Lin County, have the potential to induce esophageal cancer and precancerous gastric tumors in animals.
Some molds can reduce nitrates to nitrites and promote the formation of secondary amines, while a few can enhance the synthesis of nitrosamines in food. The toxins produced by Alternaria alternata can activate the human embryonic esophageal cancer gene and successfully induce squamous cell carcinoma of the human embryonic esophagus. In addition, moldy foods were found in the homes of residents in high-risk areas, including samples of Mucor, Aspergillus flavus, and Rhizopus. The combined action of mold toxins and nitrosamines results in a synergistic carcinogenic effect.
(3) Investigation has shown that residents’ diets lacking fresh vegetables, fruits, and animal-based foods result in deficiencies of certain nutrients, including certain vitamins and trace elements.
Vitamin A plays a role in maintaining normal structure and function of epithelial tissues. Its deficiency can cause hyperplasia and hyperkeratosis of the gastric and esophageal epithelium in rats, and can promote the development of gastric cancer induced by methylcholanthrene in mice. Riboflavin deficiency significantly enhances the induction of esophageal cancer by nitrosamines in rats. Vitamin C and E can inhibit the nitrosation of amines both in vivo and in vitro, and can suppress the carcinogenic effects of nitrosamines on the esophagus. Residents in high-risk areas have diets that are deficient in vitamins A, C, E, riboflavin, and carotenoids, as well as trace elements such as selenium, molybdenum, and zinc, which weakens the body’s disease prevention and anti-cancer capabilities.
(4) There is a significant family aggregation of esophageal cancer in high-incidence areas of China, and research has proven that genetic factors also play an important role in the disease. It is thus believed that esophageal cancer is a disease caused by the combined effects of environmental and genetic factors.
(5) Dietary habits:
Eating coarse and hard food, consuming food at high temperatures, and eating too quickly may cause damage to the esophagus. Ignoring oral hygiene may lead to esophageal inflammation, which is a contributing factor to esophageal cancer.
(6) Smoking and drinking:
European scientists believe that smoking and drinking are the main risk factors for esophageal cancer, and Chinese researchers support the idea that smoking is one of the factors contributing to the development of esophageal cancer. Alcohol itself has carcinogenic or co-carcinogenic effects and may contain pollutants and impurities. Different types of alcohol may contain different pollutants, such as trace elements, mold toxins, and nitrosamines. European studies have shown that people who smoke and drink are more likely to develop esophageal cancer than those with a single habit.