A daily supplement of a green tea extract, providing 640 milligrams of polyphenols, may reduce the oxidative damage associated with strength training, according to findings published in Nutrition Research.
The study adds to the long list of potential health benefits of green tea and its extracts. The Polish researchers who led the new study proposed that supplements of green tea extract "can potentially be recommended to persons who are just beginning to train".
Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.
Researchers from the Jozef Pilsudski University of Physical Education in Warsaw report that green tea extract may protect untrained people who start training from muscle damage associated with oxidative stress.
Oxygen-breathing organisms naturally produce reactive oxygen species (ROS), which play an important role in a range of functions, including cell signaling. However, over production of these ROS from smoking, pollution, sunlight, high intensity exercise, or simply aging, may overwhelm the body’s antioxidant defenses and lead to oxidative stress.
"It has been suggested that exercise-induced oxidative stress may be associated with muscle fatigue, muscle damage, and a decrease in physical performance," explained the researchers.
The Warsaw-based scientists evaluated the effects of four weeks of green tea extract supplementation on markers of oxidative stress and muscular damage in men after short-term exercise.
Thirty-five were recruited and randomly assigned to receive either the green tea extract or placebo in combination with strength training.
Results showed that the green tea extract was associated with increased levels of polyphenols in the blood, and the subjects' total antioxidant status increased accordingly.
Markers of oxidative stress like lipid hydroxyperoxides were seen to increase as a result of exercise, but only in the placebo group. No such increases were recorded in the green tea group.
Neither group displayed any effects on muscular endurance but the green tea extract was associated with an improvement in exercise tolerance.
"Furthermore, supplementation with green tea extract prevented oxidative stress induced by long-term strength training in our previously untrained men," wrote the researchers.
"Further studies are needed to confirm our finding using a more damaging exercise protocol and well-trained participants, because the validity of antioxidant supplementation for attenuating exercise-induced oxidative stress and muscle injury in athletes has been questioned," they concluded.
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