The World Health Organization has already listed alcohol as a first-class carcinogen, and the main evidence comes from two aspects. The results of large-scale epidemiological studies show that the more people drink, the higher the risk of cancer. Then there are animal experiments. Adding alcohol to the drinking water of mice will obviously increase the cancer rate of mice. The question of how alcohol causes cancer seems simple, but not many people actually know the answer. Even people who call for abstinence don't know why drinking alcohol can cause cancer. Actually, alcohol itself is not a carcinogen. The real danger is that its metabolite acetaldehyde in the body is an obvious carcinogen. At present, acetaldehyde has at least two important carcinogenic factors, namely, acetaldehyde can directly combine with DNA to cause DNA mutation and acetaldehyde can cause cell death in vivo, induce chronic inflammation and cell replication, and increase the probability of cancer. Drinking alcohol is more likely to cause cancer for people in China, because 60% of people in Asia lack acetaldehyde invertase. The slower the conversion rate of acetaldehyde, the longer it stays in the body, and the greater the harm to human body. Regarding the problem between cancer and health, the World Health Organization has already reached a formal conclusion. There are five words, the less alcohol, the better. According to the collaborative research of the World Health Organization, under normal circumstances, the amount of pure alcohol consumed by men should not exceed 20g, and women should be less. If drinking is inevitable, experts suggest that it is best to choose drinks with low alcohol concentration as far as possible instead of drinking on an empty stomach, and eat foods rich in vitamins and high protein before drinking.