A 2009 study by Iranian researchers pointed out that drinking a cup of hot tea daily increases the risk of esophageal cancer. Moreover, when the tea temperature is between 65°C and 69°C, the risk of esophageal cancer doubles; once the tea temperature exceeds 70°C, the risk increases by 8 times. If tea is consumed within 2 minutes after being poured, the risk of developing esophageal cancer is about 5 times higher than if waited for 4 minutes. Another study found that drinking tea at a temperature between 56°C and 60°C is more beneficial to health. Besides the risk from high temperature, Taiwanese nutritionist Zhang Silan reminds that pesticide residues on tea leaves may also be harmful. To reduce pesticide concerns, it is recommended to discard the first brew and to keep the lid off while steeping, allowing some pesticide residues to evaporate with the steam. When purchasing tea, choosing organic varieties is safer. So, what is the principle behind tea's cancer-preventive effects, and which cancers can be prevented by drinking tea in daily life?

1. How to prevent cancer by drinking tea

1.1 The anti-cancer effect of green tea

Domestic and international studies have shown that various types of tea have different degrees of preventive effects against chemically induced or metastatic tumors in experimental animals. Both endogenous and exogenous free radicals can cause cancer, but natural antioxidants can scavenge free radicals, thus attracting attention for their anti-cancer potential. Green tea is rich in natural antioxidants such as "tea polyphenols." Consumed before or after meals, these antioxidants work synergistically to scavenge free radicals, enhancing green tea's anti-cancer effects.

 

 

1.2 "Green tea polyphenols" are key anti-cancer compounds in green tea

The content of green tea polyphenols in green tea is five times that of ordinary tea. Green tea can reduce the incidence of certain cancers, but scientists previously did not know exactly which substances were responsible for the preventive effect, nor could they determine the optimal daily intake for effectiveness.

Green tea polyphenols may be only one of the anti-cancer substances in green tea. Researchers also found that the molecular structure of green tea polyphenols is similar to that of the anti-cancer drug methotrexate.

DHFR is crucial for both healthy and cancer cells. Green tea polyphenols bind strongly to DHFR, but less so than methotrexate, thus causing fewer side effects on healthy cells than the drug.

 

 

1.3 The anti-cancer effect of Pu'er tea

After comparing the effects of various green teas, researchers found that Pu'er tea has a stronger ability to kill cancer cells. Long-term consumption of Pu'er tea by cancer patients led to changes in cancer cells: they shrank and became round, pseudopodia reduced, losing adhesion and migration ability, and some even detached and disappeared. Remaining cells became smaller and rounder, with nuclear condensation, chromatin clumping or disappearance, vacuoles in the nucleus and cytoplasm, nucleolar condensation or fragmentation, chromosome contraction or clumping, reduced ribosomes, dilation of mitochondria and endoplasmic reticulum, reduced RNA synthesis, and cessation of nuclear division. These changes indicate that cancer cells degenerate and tend to die under the pharmacological action of Pu'er tea.

 

 

2. Which cancers can be prevented by drinking tea?

2.1 Drinking tea prevents prostate cancer

Recent studies show that both black tea and green tea can help prevent prostate cancer, as well as lower cholesterol, reduce cell damage caused by smoking, and even prevent heart disease.

Researchers investigated 20 male patients with prostate cancer who drank 5 cups of black or green tea daily before surgery. Analysis of their blood and prostate tissue after surgery revealed higher levels of phenolic compounds. Adding black tea, green tea, or soda to cancer cell cultures significantly slowed cancer cell growth.

 

 

2.2 Drinking green tea benefits ovarian cancer prevention

Researchers from Australia and China recently discovered through experiments that green tea can reduce the incidence of ovarian cancer in women. Women who drink green tea daily have nearly 60% lower risk of ovarian cancer compared to non-drinkers.

Researchers from Curtin University in Australia and Zhejiang Cancer Hospital in China conducted experiments on 900 women, of whom 254 had ovarian cancer and 652 were healthy. The results showed that daily tea consumption, especially green tea, significantly reduces the risk of ovarian cancer. Besides tea, other factors such as smoking, oral contraceptives, physical activity, and family history of ovarian cancer also influence the risk.

 

 

2.3 Drinking green tea can prevent skin cancer

Researchers at Dartmouth Medical School in New Hampshire, USA, recently found that drinking several cups of tea daily can reduce the risk of two common skin cancers.

According to Reuters, the research team led by Judy Rees studied the dietary habits and health status of 2,200 adults and found that tea drinkers had a lower risk of squamous cell carcinoma and basal cell carcinoma. Those who drank more than one cup of tea daily had a 20% to 30% lower risk of these two cancers compared to non-tea drinkers.

The study suggests that tea contains an antioxidant called EGCG, which limits the damage of ultraviolet radiation to the skin. This effect was more pronounced in people who had been drinking at least two cups of tea daily for decades.

Experts point out that this finding does not mean you can skip sunscreen. There is no evidence that drinking tea reduces the risk of skin cancer in people who frequently experience sunburn.