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Green tea extract may boost ‘metabolic efficiency’ and help endurance training: Human data

By Stephen Daniells+

27-Jan-2015
Last updated on 27-Jan-2015 at 14:07 GMT2015-01-27T14:07:45Z

Green tea extract may boost ‘metabolic efficiency’ and help endurance training: Human data

Supplements of green tea extract may enhance performance in active men by improving metabolic efficiency and economy, says a new study.

Green tea extracts also led to greater body fat reductions compared to placebo, reported researchers from the Anglia Ruskin University and the University of Hertfordshire in England in the Journal of the International Society of Sports Nutrition .

“The use of a capsulated decaffeinated green tea extract formula in the present study potentially offers a more practical means to regularly consume a sufficient daily dosage to elicit such effects (compared to consumption of about 6-7 cups of green tea per day, especially considering the notable variability of catechin content in commercial green teas),” they wrote.

Tea benefits

The study adds to an ever-growing body of science supporting the potential benefits of green tea (Camellia sinensis) and its constituents, most notably EGCG (epigallocatechin gallate).

Green tea contains between 30% and 40% of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3% and 10%. Oolong tea is semi-fermented tea and is somewhere between green and black tea. The four primary polyphenols found in fresh tealeaves are EGCG, epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC).

Studies investigating the potential exercise-enhancing benefits of green tea extracts have yielded conflicting results, said the authors of the new JISSN paper, with caffeine being a significant complication. For their new study, they chose to use a decaffeinated green tea extract (571 milligrams per day), obtained from Changsha Active Ingredients Group Inc. in China. The extract provided an EGCG dose of 400 mg per day.

Study details

"The use of [the green tea extract] resulted in a progressive increase in distance covered from 20.2 km at week 0 to 22.4 km by week 4, representing a 10.9% significant increase in performance," reported the researchers.

Led by Justin Roberts, the researchers recruited 14 recreationally active men with an average age of 21 to participate in their study. The men received either placebo or the green tea extract for four weeks and to cycle for one hour three times per week.

Results showed that fat oxidation rates increased by almost 25% in the green tea extract group, but no changes were observed in the placebo group.

In addition, significant decreases in body fat were observed in the green tea extract group (1.63%), in contrast to the placebo group.

Performance improvements were also observed, with the green tea extract group covering a longer distance in the final testing at week four (a 10.9% improvement).

“Decaffeinated green tea extract in conjunction with exercise training reduced relative fat oxidation rates and body composition in recreationally active, male volunteers,” wrote the researchers. “Improved metabolic efficiency during submaximal exercise may potentiate improved metabolic economy and hence adherence to longer term training programmes.

“Combined with the observed impact of decaffeinated green tea extract on subsequent performance indices, this supports the contention that EGCG use may modulate cellular signalling pathways leading to more efficient substrate use, resulting in improved exercise output.”

The study was funded by British sports nutrition brand High5 Ltd.

Source: Journal of the International Society of Sports Nutrition
2015, 12:1, doi:10.1186/s12970-014-0062-7
“The effect of a decaffeinated green tea extract formula on fat oxidation, body composition and exercise performance”
Authors: J.D. Roberts, M.G. Roberts, M.D. Tarpey, et al. 

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