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27.01.2023

Tea protects against glioma

Tea drinkers may be less likely to have glioma - a typically ill-treatable form of brain cancer - than non-tea drinkers. This is suggested by an Indonesian meta-study.

Study
Raymond Pranata, a biomedical researcher from the Universitas Pelita Harapan in Indonesia, collected 13 previously published epidemiological studies, in which researchers had tried to measure the effect of coffee and tea intake on glioma. In his publication, which appeared in the British Journal of Nutrition in 2023, Pranata swept the results together and re-analyzed them.

Results
The researchers found a trend that coffee drinkers were less likely to have glioma than non-coffee drinkers, but the difference between the two groups was not statistically significant.

However, the difference between the probability of glioma in the tea drinkers and the probability in study participants who drank little or no tea was statistically significant.

This is clear in the table below. Click on it for a larger version.

The more cups of tea the study participants drank, the lower their chance of glioma.

Mechanism
Polyphenols such as ECG and EGCG in tea inhibit inflammation and the development of cancer cells. In addition, they have an antioxidant and - in fundamental research - a cancer-inhibiting effect.

In cancer cells, as the the result of a methylation prcess, the gene for O6-methylguanine-DNA-methyltransferase is often no longer active. In in vitro research, cancer cells after being exposed to EGCG screw off those methyl groups of the gene, making it active again.

"Higher O6-methylguanine-DNA-methyltransferase activation is postulated to protect against the development of various cancers, including glioma," the researchers write.

Conclusion
The researchers emphasize that the results of their meta-study rely heavily on cohort studies. "Confounders are present in the observational studies on lifestyle, and these confounders might not be adequately reported and adjusted," they write.

It seems that we have to take the results of this study with a grain of salt for the time being.

Source:
Br J Nutr. 2022 Jan 14;127(1):78-86.

More:
High intake of nuts and legumes protects against brain cancer 16.01.2023
Walking and running can halve the chance of brain cancer 18.05.2014

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Cancer Prevention
Tea

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