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Green tea for sports nutrition?

By Stephen Daniells , 15-Apr-2008

Antioxidant-rich green tea may counter the effects of resistance exercise by reducing the detrimental effects of oxidative stress, suggests a small trial from Brazil.

If the results can be repeated in a bigger trial it could see green tea added to the market for energy drinks and sports nutrition, which has blossomed over the last few years. While the thought of athletes knocking back a cup of green tea after a workout may seem strange, it may signal a possibility for antioxidant-rich green tea extracts to be formulated in sports drinks, and supported by science like the new study from the May issue of the journal Nutrition. Researchers from the Federal University of Santa Catarina, and the Center of Physical Education, Physiotherapy and Sports of Santa Catarina State University studied the effects of daily green tea consumption for seven days in athletes undertaking resistance training, which can increase the production of free radicals beyond the tissues' antioxidant defense capacity, and causing oxidative stress. "The inadequate intake of dietary antioxidants among the physically active populations must be considered," wrote lead author Vilma Simoes Pereira Panza. "This study suggests that green tea intake may offer a protective effect against oxidative damaged induced by resistance exercise." According to market analyst Mintel, the sports drink market in the UK was worth £137m ($252m, €200m) in 2003, and is dominated by isotonic drinks like Lucozade Sport, Powerade and Gatorade. In the US, the sports drinks market is reported to have generated almost $3bn (£1.6bn, €2.4bn) with Gatorade dominating the market with 82 per cent of the market. Powerade is a distant second with a reported 13 per cent of the market. Study details Panza and co-workers recruited 14 healthy men aged between 19 and 30 to consume either water or green tea three times per day for seven days. The average polyphenol content of the tea was 771.0 micrograms per mL, while the average intake of green tea polyphenols was calculated to be 4.6 micrograms per day. After seven days of consuming the beverages, the volunteers were required to perform a bench press exercise (four sets, 10 to 4 repetitions). The researchers analysed blood samples and calculated the total antioxidant capacity according to the ferric reducing ability of plasma (FRAP) assay, and levels of reduced glutathione and lipid hydroperoxide. According to the results, consumption of green tea was associated with a 64 per cent reduction in the levels of lipid hydroperoxide after exercise, while blood levels of polyphenols were approximately 27 per cent high before and after exercise. Moreover, post-exercise levels of glutathione, a protein that is important in protecting the body from oxidative (free radical) damage, were approximately 37 per cent higher in the green tea group. "There is evidence that supplementation with antioxidants may decrease the oxidation of blood GSH after exercise," stated the researchers. "Furthermore, our findings demonstrate that dietary strategies, such as daily GT intake, may also benefit the glutathione system of athletes by elevating blood GSH levels before and after effort." Consumption of green tea also provided pre-exercise benefits, with the pre-exercise FRAP value about 21 per cent higher compared with the control group. "Consumption of green tea, a beverage rich in polyphenols, may offer protection against the oxidative damage caused by exercise, and dietary guidance for sports participants should be emphasised," concluded the researchers. Panza and co-workers also noted that future studies should elucidate the time course and recovery periods associated with green tea consumption, while other studies "should corroborate our findings using other polyphenol-rich foods and beverages, thus widening the dietary strategies applied to training." Green tea market According to recent report from Frost & Sullivan, the market for green tea extracts, currently worth around $44m (€29.7m), is expected to grow by more than 13 per cent over the next seven years. The analysts state that science is the reason for the ingredient's growing popularity, and that it is generally accepted that green tea has a beneficial role in reducing Alzheimer's, certain cancers, cardiovascular and oral health. Source: Nutrition (Elsevier) May 2008, Volume 24, Issue 5, Pages 433-442 "Consumption of green tea favorably affects oxidative stress markers in weight-trained men" Authors: V.S. Pereira Panza, E. Wazlawik, G.R. Schutz, L. Comin, K.C. Hecht, E.L. da Silva

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