Many people know that drinking tea can prevent cancer, but in fact, drinking tea can also potentially cause cancer. Today, the editor will explain which types of tea are more likely to be carcinogenic.
Iranian researchers published a study in 2009 pointing out that drinking a cup of hot tea daily can easily increase the risk of esophageal cancer. Moreover, when the tea water temperature is between 65°C and 69°C, the risk of esophageal cancer doubles. Once the water temperature exceeds 70°C, the incidence of esophageal cancer increases eightfold. If the tea is consumed within 2 minutes of being poured, the risk of developing esophageal cancer is about five times higher than if you wait for 4 minutes before drinking. Another study found that a tea temperature between 56°C and 60°C is more beneficial to health.
In addition to the risk of cancer from excessively hot tea, Taiwanese nutritionist Zhang Silan reminds us that pesticide residues in tea leaves can also be harmful to health. If you are concerned about pesticide residues, you can discard the first infusion. When brewing, leave the lid open to trap the steam, allowing some pesticide substances to evaporate. When purchasing tea, try to choose organic tea for greater safety. So, what is the principle behind tea's cancer-prevention effects, and which types of cancer can be prevented by drinking tea in daily life?
1. The Cancer-Prevention Effects of Green Tea
Some studies at home and abroad have shown that all types of tea have varying degrees of preventive and therapeutic effects on chemical carcinogenesis or metastatic tumors in experimental animals. Both endogenous and exogenous free radicals are carcinogenic, but natural antioxidants can scavenge free radicals. Therefore, the cancer-prevention and anti-cancer effects of these natural antioxidants have garnered significant attention. Green tea is rich in natural antioxidants such as "tea polyphenols." When consumed before or after meals, various antioxidants work synergistically to scavenge free radicals, which further enhances the cancer-prevention and anti-cancer effects of green tea.
2. "Green Tea Polyphenols" are an Important Substance in Green Tea's Anti-Cancer Effect
The content of green tea polyphenols in green tea is five times that of ordinary tea. Green tea can reduce the occurrence of certain cancers, but scientists in the past did not understand which substance was responsible for the preventive effect or how it worked. Therefore, they could not determine how much green tea a person should drink per day to be effective.
Green tea polyphenols may be just one of the many anti-cancer substances in green tea. They also discovered that the molecular structure of green tea polyphenols is similar to that of the anti-cancer drug methotrexate.
DHFR (dihydrofolate reductase) is crucial for both healthy and cancer cells. Green tea polyphenols have a strong binding affinity for DHFR, but it is weaker than that of methotrexate, so the side effects on healthy cells are smaller than those of the anti-cancer drug.
3. The Cancer-Prevention Effects of Pu-erh Tea
After comparing the effects of various green teas, it was determined that Pu-erh tea has a stronger effect in killing cancer cells. After cancer patients drink Pu-erh tea for a long period, their cancerous cells shrink from polygonal to round, their pseudopods decrease in number, and they lose their ability to adhere and migrate. Some even detach, float, and are lost. The remaining cells become smaller, rounder, and more concentrated, with pyknosis (shrinkage of the nucleus), condensation or disappearance of chromatin, vacuoles appearing in the nucleus and cytoplasm, pyknosis or fragmentation of the nucleolus, contraction or condensation of chromosomes, a reduction in ribosomes, and expansion of mitochondria and endoplasmic reticulum. RNA synthesis decreases, and nuclear division ceases. These changes demonstrate that under the pharmacological action of Pu-erh tea, cancer cells tend towards death through degeneration.