Green Tea Discovery Upends Ideas About Its Health Benefits

New research casts doubt on previous assumptions about how the ingredients in green tea work to promote health.

Green tea has long been known to have health benefits. In particular, it contains catechins called ECG and EGCG which are said to extend life.

These two substances belong to the group of polyphenols. It is considered an antioxidant, which means that it combats or prevents oxidative stress in the body caused by aggressive oxygen free radicals.

Until now, researchers hypothesized that catechins neutralize these free radicals and thus prevent cell or DNA damage. One of the sources of free radicals for oxygen is metabolism. For example, when mitochondria – the centers of power in the cell – work to produce energy.

In the new study in the journal agingResearchers have shown that polyphenols from green tea initially increase oxidative stress in the short term, but this has a subsequent effect in increasing the defensive capabilities of cells and the organism. As a result, the catechins in green tea that the researchers fed to the nematodes led to longevity and fitness.

says study leader Michael Resto, professor of energy metabolism in the Health Department of Science and Technology at ETH Zurich.

However, this increase in defense capacity does not appear through the immune system, but through the activation of genes that produce specific enzymes such as superoxide dismutase (SOD) and catalase (CTL). It is these enzymes that inactivate free radicals in nematodes. They are mainly endogenous antioxidants.

Resto was not surprised to see this kind of mechanism in action. His research group showed in 2009 that the reason why sport promotes health is that sports activities increase oxidative stress in the short term, thus improving the body’s defenses.

Consuming fewer calories has the same effect, as has been shown several times in animals. Mice fed a low-calorie diet lived longer than those fed a normal high-calorie diet. “So it made sense for me that the catechins in green tea would work in a similar way,” Risto explains.

He went on to say that the results of this study translate well to humans. The basic biochemical processes by which organisms neutralize free radicals of oxygen are preserved in evolutionary history and are present in everything from single-celled yeast to humans.

Ristow himself drinks green tea every day, a practice he recommends. But it is advised not to take green tea extracts or concentrates. “At a certain concentration, it becomes toxic,” he says. High doses of catechins inhibit mitochondria to such an extent that they lead to cell death, which can be especially dangerous in the liver. Anyone who consumes these polyphenols in excessive doses risks damaging their organs.

While most catechins are found in Japanese green teas, other green teas also contain adequate amounts of these polyphenols. On the other hand, black tea contains a much lower level of catechins, as they are largely destroyed by the fermentation process.

“This is why green tea is better than black tea,” says Resto.

Additional co-authors are from the University of Jena and ETH Zurich.

This article was originally published by ETH Zurich. Reposted via


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