The Catechin Paradox

Green tea catechins have been found to have a "paradoxical" benefit

Maria Azarova, Naked Science

The most common polyphenols found in green tea leaves are epigallocatechin gallate (EGCG), epicatechin gallate, epigallocatechin and epicatechin: they make up up to 42% of its extract and are considered antioxidants. Consequently, they prevent damage to cells in the body, the so-called oxidative stress. Earlier experiments on various model organisms have shown that catechins have a positive effect on life expectancy due to metabolic adaptation and increased resistance to reactive oxygen species. For example, an additive in the form of extracts of green tea rich in EGCG affected glucose metabolism and strengthened the health of fruit flies. And, the water containing polyphenols of this drink helped male mice to live longer.

Researchers from the Swiss Higher Technical School of Zurich and the Friedrich Schiller University of Jena in Germany decided to check whether green tea catechins really work exactly as we think, and in what concentrations they are useful. The results of the work are published in the journal Aging (Tian et al., Green tea catechins EGCG and ECG enhance the fitness and lifespan of Caenorhabditis elegans by complex I inhibition).

Experiments were carried out on free-living soil nematodes Caenorhabditis elegans and mice. As it turned out, polyphenols increased oxidative stress in the short term, but then improved the protective capabilities of cells. "Catechins after 6-12 hours hindered the respiration of C.elegans mitochondria and the activity of complex I in isolated rodent mitochondria. Violation of mitochondrial respiration was accompanied by a short-term drop in the production of adenosine triphosphate and a temporary increase in the level of reactive oxygen species (ROS) in nematodes. After 24 hours, mitochondrial respiration and adenosine triphosphate levels recovered, and ROS indicators even fell below the control conditions," the researchers write. Epigallocatechin gallate and epicatechin gallate improved the physical fitness of the subjects and increased their life expectancy — and this was achieved already at a dosage of 0.0025 millimoles per liter.

From this, the researchers conclude that green tea polyphenols are not actually antioxidants (substances that inhibit oxidation), but pro-oxidants, that is, they cause oxidative stress and, as a result, improve the body's ability to defend itself. And not at the expense of the immune system, but through the activation of genes that produce enzymes like superoxide dismutase and catalase, which inactivate free radicals and, in turn, act as endogenous antioxidants.

However, the authors do not recommend taking green tea extracts or drinking concentrates. "Catechins in high doses suppress mitochondria to such an extent that cell death occurs. This can be especially dangerous for the liver and threatens to damage organs," said Professor Michael Ristow.

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