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Recent research challenges previous beliefs about the health benefits of green tea.
It has been long known that green tea has health benefits. It contains catechins, EGCG and ECG that are believed to prolong the life expectancy.
These two substances are part of the group called polyphenols. They are called antioxidants. This means that they prevent or counter oxidative stress caused by oxygen-aggressive free radicals.
Researchers have believed that catechins neutralize free radicals and prevent DNA damage. The metabolism is one source of oxygen-free radicals. For example, the mitochondria (powerhouses in the cellare) are producing energy.
The researchers found that green tea polyphenols increase oxidative stress initially, but then have the effect of increasing the defense capabilities of cells and organisms. Researchers found that the catechins found in green tea were able to prolong life and improve fitness.
This means that green tea polyphenols or catechins are not antioxidants. Instead, they act as pro-oxidants to improve an organism's ability to defend itself. It is similar to a vaccine, according to Michael Ristow (professor of energy metabolism, health sciences and technology, ETH Zurich).
This increase in defense capability is not due to the immune system. It's actually caused by activating genes that make certain enzymes like superoxide dismutase and catalase. These enzymes are endogenous antioxidants and inactivate free radicals in the Nematode.
Ristow doesn't find it surprising that this mechanism is at work. In 2009, Ristow's research team found that sport promotes health because it increases oxidative stress in the short-term and improves the body's defenses.
As has been proven in animal studies, consuming fewer calories can have the same effect. Mice who are fed a lower-calorie diet live longer that mice who are fed high-calorie, normal-calorie foods. Ristow says that it was intuitive to me that catechins in green-tea would also work in this way.
He says that the results of this study are applicable to humans. The fundamental biochemical processes that organisms use to neutralize oxygen free radicals have been conserved throughout evolutionary history. They are found in all life forms, from yeast unicellular to humans.
Ristow drinks green tea every morning, which he highly recommends. He advises against drinking green tea concentrates or extracts. It becomes toxic at a certain level, he states. High-dose catechins can cause cell death by inhibiting mitochondria. This is especially dangerous for the liver. Consuming these polyphenols in high amounts can cause organ damage.
The highest levels of catechins can be found in Japanese green teas, but other types of green teas contain enough polyphenols. The fermentation process has largely destroyed catechins in black tea.
Ristow states that green tea is better than black tea.
Additional coauthors come from the University of Jena, ETH Zurich, and University of Jena.
Source: ETH Zurich