Can tea prevent cancer?
The new answer may be unexpected. In the forthcoming August issue of the European Journal of Epidemiology, scientists from the Peking University School of Medicine, Peking Union Medical College and Harvard University and other world-renowned medical schools published an article on “The difference between tea consumption and cancer risk.” Relationship: An academic research paper on a prospective cohort study of 500,000 Chinese adults gives a surprising analysis of the results. Drinking tea may not be effective in preventing cancer.
Tea is a commonly used drink in all types of people in China. In vitro and in vivo experiments have demonstrated that tea polyphenols can prevent cancer by anti-oxidation, growth inhibition and apoptosis induction. However, according to evidence from human studies, the link between tea consumption and cancer risk remains controversial. The large-scale epidemiological survey led by Li Liming, director of the former Chinese Center for Disease Control and Prevention and professor of Peking Union Medical College, recruited 455,981 Chinese in five cities and five rural areas between China and China from 2004 to 2008. Residents, whose average age is 50.9 years old, 36.1% of volunteers are male and 56.1% of volunteers live in rural areas. The researchers used questionnaires to record the amount of tea they usually drink, followed by long-term follow-up, to observe the number of cancers during follow-up, and to analyze whether the habit of drinking tea is related to the incidence of all cancers, and the six major types of Cancer (lung cancer, stomach cancer, colorectal cancer, liver cancer, female breast cancer and cervical cancer)?
After removing some of the volunteers who did not meet the requirements, the researchers performed a statistical analysis of the data of the remaining 450,000 subjects. Each volunteer will fill out a detailed questionnaire during the initial enrollment and follow-up process, including smoking, drinking, tea, eating habits, education, marital status, occupation, income status, physical exercise, Basic diseases (diabetes, heart disease, cerebrovascular disease, gastric ulcer, chronic hepatitis, gallstones), fertility and family history of cancer are very detailed. At the same time, regarding tea drinking, the classification and registration of the specific conditions are carried out. The type of tea, the frequency of tea, the weight of tea added each time, the temperature of tea when drinking tea (hot water, hot water, warm water) , room temperature, etc.)
After a follow-up observation of 10.1 years, a total of 22,652 cancer patients were found, including 4046 cases of lung cancer. 2366 cases of gastric cancer, 2267 cases of intestinal cancer, 1874 cases of liver cancer, 1984 cases of breast cancer and 868 cases of cervical cancer. Among male volunteers, a higher proportion of people who like to smoke and drink alcohol also love to drink tea. This may be related to folklore. “Drinking tea can sober up, can moisturize the lungs, and can reduce the carcinogenic effect of tobacco and alcohol. “This traditional concept is related.
After a rigorous statistical analysis, the Chinese team of scientists has three major discoveries:
One is compared to volunteers who don’t drink much tea (the frequency of tea is less than once a week), then volunteers who drink tea almost every day and add tea with an average weight of more than 4g/day, lung cancer and stomach cancer The risk is significantly higher. Among them, the risk of lung cancer increased by 31%, and the risk of gastric cancer increased by 18%. However, it has no effect on the risk of bowel cancer, liver cancer, breast cancer, and cervical cancer. This conclusion is also true among male volunteers. In female volunteers, there is no significant association between tea and cancer risk. .
Then, among the volunteers who are not exposed to alcohol and tobacco, the risk of gastric cancer is significantly increased , compared with those who do not drink tea much, who drink tea almost every day and add tea with an average weight of more than 4g/day. 46%; however, it has no effect on lung cancer, colon cancer, liver cancer, breast cancer, and cervical cancer.
Third, among the volunteers who smoked and drank alcohol, compared with those who did not drink tea much, volunteers who drank tea almost every day and added tea with an average weight of more than 4g/day had a significant increase in the risk of cancer, especially lung cancer. . Drinking tea does not significantly reduce the risk of cancer, which means that drinking tea does not solve the poison of tobacco and alcohol.
In a nutshell: drinking tea at high frequency may increase the risk of lung cancer and stomach cancer , but it does not seem to have much effect on the occurrence of other common cancers; one thing that is clear is that in this research population, drinking more tea People tend to smoke and drink too much. If you do not rule out the two factors of smoking and drinking, you will think that drinking tea is related to the increased risk of cancer. That tea is a black pot for tobacco and alcohol.
Drinking tea does not offset the carcinogenic effects of tobacco and alcohol!
Summarize the survey, that is, people who drink more tea have more cancer than those who drink less tea! The overall risk of cancer increases, and the risk of lung cancer and gastric cancer increases in each category; the risk of colorectal cancer, liver cancer, breast cancer, and cervical cancer is similar regardless of tea consumption.
However, the above paper does not show the type of tea, the temperature of tea when drinking tea and the correlation between cancer; research in this area has also been the focus of scholars at home and abroad in recent years.
Drink hot tea: significantly increase the risk of esophageal cancer
Esophageal cancer, especially esophageal squamous cell carcinoma, is a high-grade malignant tumor in East Asia. It is a cause of esophageal cancer caused by smoking, drinking, and long-term consumption of “hot food” (hot tea, hot drinks, mala, hot pot, etc.). An important risk factor.
In fact, the team led by Director Li Liming last year published the results of a study on the risk of drinking hot tea and esophageal cancer in the Journal of Internal Medicine. Using a questionnaire similar to the above study, they surveyed and tracked 456 155 30-79 healthy volunteers, with an average follow-up of 9.2 years and a total of 1731 patients with esophageal cancer.
Among male volunteers, those who drink tea almost every day have an increased risk of esophageal cancer compared with those who drink tea less than once a week: volunteers who drink warm water tea once a day, risk of esophageal cancer Increased by 17%; volunteers who drink hot tea once a day, the risk of esophageal cancer increased by 30%; volunteers who drink hot tea directly every day, the risk of esophageal cancer increased by 55%. Moreover, the risk of esophageal cancer increases significantly with the frequency and amount of hot water, hot water, and tea – however, in female volunteers, drinking tea does not seem to increase the risk of esophageal cancer.
As mentioned above, some people who smoke and drink alcohol drink tea to soothe and moisten their lungs. Therefore, a considerable number of volunteers have the hobby of smoking, drinking and drinking tea. Compared with volunteers who ate less than 1 tea per week on average and consumed less than 15g per day, those who drank more than 15g of tea per day and liked boiling hot blisters had the highest risk of esophageal cancer. Times. By the same token, the risk of esophageal cancer has more than doubled compared to volunteers who don’t smoke much or drink tea, and who love to smoke and drink hot blisters. In volunteers who neither smoke nor drink, drinking tea does not increase the risk of esophageal cancer.
A case-control study by another Iranian scientist found similar results: Professor Reza Malekzadeh from the University of Tehran, led a team that analyzed 300 patients with esophageal cancer, 571 neighbors with esophageal cancer, and 48,582 healthy volunteers. Eating habits, they found that volunteers who like hot tea have a 103% increased risk of esophageal cancer compared to those who do not drink tea or drink tea after they have cooled down. They like to drink hot boiled tea. The risk of esophageal cancer in volunteers has increased more than eightfold.
Integrated together, we can find: a cup of tea itself probably does not increase the risk of esophageal cancer, but if you smoke, drink alcohol, but also looking forward to “drink tea may counteract the carcinogenic role of research,” you might clever wisdom wrong – in Among the people who smoke and drink, high-frequency drinking hot water or hot boiling water, significantly increase the risk of esophageal cancer.
Drink green tea to reduce the risk of gastric cancer? Chinese and Japanese scholars’ conclusions are the opposite
Different tea leaves contain different ingredients. Green tea contains more catechins and tea tannins. These substances can resist oxidation and thus prevent cancer to a certain extent. Professor M Inoue from the National Cancer Center of Japan summarized data from six large prospective observations. A total of 219 080 volunteers were included. The average follow-up was followed for more than 10 years. A total of 3577 patients with gastric cancer were found.
The results suggest that in male volunteers, drinking hot tea has nothing to do with the risk of gastric cancer; among female volunteers, those who drink more than 5 cups of green tea a day have a significantly lower risk of gastric cancer, a 21% reduction.
This conclusion seems to be inconsistent with the research conducted by Director Li Liming in the Chinese population: Professor Li’s team found that drinking tea seems to increase the risk of gastric cancer, while Japanese scholars’ research suggests that at least among female volunteers, Green tea can reduce the risk of stomach cancer – why is there such an opposite conclusion? The main reason may be that Li’s team did not strictly distinguish between different types of tea (green tea, black tea, black tea, white tea, green tea, yellow tea), but bundled together; at the same time, there is no detailed distinction between different genders. .
Drink black tea: or increase breast cancer risk
The black tea in English does not correspond to the “black tea” that Chinese people often say; in fact, what foreigners want to say is “black tea.” Black tea contains a certain concentration of caffeine, which may interfere with the metabolism and function of sex hormones, and thus may indirectly affect malignant tumors related to hormone secretion such as breast cancer.
As early as 1996, the National Cancer Center magazine published a famous study. The Dutch scholars carried out a total of 58,279 male healthy volunteers and 62,573 female volunteers, aged between 55 and 69 years old. Follow-up of the year. It was found that female volunteers who like to drink black tea (women who drink more than 5 cups of black tea a day) tend to have a greater probability of developing breast cancer, and the risk of breast cancer increases by 30%. Drinking black tea does not seem to be related to the risk of other cancers such as bowel cancer.
However, a similar large-scale population study conducted in Sweden in 2012 showed that drinking black tea or a beverage containing a higher concentration of caffeine did not affect breast cancer-specific mortality and survival. Coincidentally, in 2013, the Shenyang Women and Infant Hospital scholars conducted a summary analysis of the current research on the relationship between black tea and breast cancer. They found that there was no statistically significant correlation between drinking black tea and breast cancer. .
Therefore, the risk of black tea and breast cancer remains to be further studied.