|The supplement that was used in the study at hand was a commercially available product from Olimp Labs, a Polish producer of bodybuilding and fitness supplements.|
No one can and that's why I'd like to ask you to go back to some of the previous articles on that matter and remind yourself that there is evidence that the provision of significant amounts of supplemental antioxidant can blunt the beneficial adaptive response to exercise (learn more and even more).
Apropos "significant amounts"! If we take a look at the amount of green tea extract, the 16 male sprinters (21.6 y; 76.9kg; 11.8% body fat) received, a question arises: Are 2x250 mg of standardized GTE (245 mg polyphenols, including 200 mg catechins, among them 137 mg epigallocatechin-3-galate) a "significant amount" of green tea extract (GTE) if they are consumed twice daily?
I guess there may be supplement junkies out there who consume way more than this 1g of green tea extract everyday. Based on the dosages in studies that report beneficial effects of GTE, 1g is yet already on the high(er) side of the dosing continuum and thus unquestionably a "significant amount" of green tea extract, which was administered in a randomized controlled crossover study that was conducted during preparatory phase of yearly training cycle (after transition period) of the sprinters all of whom had more than 4 years of training experience.
What do the latest reviews say about exercise + antioxidant supplementation? In spite of the fact that you will find reviews with different undertones, the vast majority of reviewers concludes that convincing evidence of the long-assumed benefits of anti-oxidant supplementation does not exist.Whether this warrants conclusions as the one Mari Carmen Gomez-Cabrera, Michael Ristow and Jose Viña formulate in their 2012 paper(s) and "the vast majority of experimental evidence clearly advises against this supplementation" (Gomez-Cabrera. 2014), however is still a matter of open debate (Holloszy. 2012).The two 4-week treatment periods (during which half of the subjects received GTE and the other half PL, and vice versa) were separated by a 4-week washout period. The duration of the washout period was selected based on the results of one previous study (Brown. 2011), in which 6-week supplementation with higher amounts of catechins (800 mg/day) was used on obese subjects. In view of the fact that the plasma catechin concentration in this study returned to its baseline level after at least 2 weeks of washout period, we can safely assume that a 6-week washout in highly active non-obese individuals should be enough to get rid of all the effects of only 250mg of catechins.
Both GTE and PL were administered in the form of dark gelatin capsules (Olimp Labs, De˛bica, Poland), identical in appearance (i.e., size, shape, and color); the same dosage regimen was used (two capsules twice a day). One GTP capsule contained 250 mg of standardized GTE (245 mg polyphenols, including 200 mg catechins, among them 137 mg epigallocatechin-3-galate) and additional substances (maltodextrin, microcrystalline cellulose, and magnesium stearate). Therefore, each participant was administered 980 mg polyphenols daily. PL capsules contained microcrystalline cellulose, magnesium stearate, and maltodextrin instead of GTP."Compliance was measured by counting the capsules the subjects returned. Participants who returned no more than 15 % of their capsule dose were classified as "compliant". At the end of each of the two 4-week treatment periods, the sprinters performed a repeated cycle sprint test (RST) on a cycle ergometer (Ergomedic 839E, Monark, Sweden).
|Based on the food logs, the scientists decided that there were no significant nutritional differences between the two phases of the study (Jówko. 2014)|
diet for both treatment periods. During both the first and the second treatment periods (during 7 days preceding each RST), the participants filled out a 3-day dietary record (covering 2 week days and 1 day of the week end).
The performance tests were performed in the morning following 12-hovernight fast, at air temperature between 19 and 21°C and with 40–60 % relative humidity. The subjects were instructed to not perform hard physical training for 48 h and avoid drinking tea and caffeinated beverages within
24 h prior to each of the RSTs.
|Figure 1: Changes in blood indices of acid–base balance & lactate concentration induced by the repeated sprint test (49 x15 s) in sprinters (n=16) after 4-week supplementation with placebo (PL) or green tea extract (GTE; Jówko. 2014)|
|Table 1: Changes in blood parameters of oxidative stress and muscle damage induced by the repeated sprint test (49 x15 s) in sprinters (n=16) after 4-week supplementation with placebo (PL) or green tea extract (GTE; Jówko. 2014)|
- Brown, A. L., et al. "Health effects of green tea catechins in overweight and obese men: a randomised controlled cross-over trial." British Journal of Nutrition 106.12 (2011): 1880-1889.
- Gomez-Cabrera, Mari Carmen, Michael Ristow, and Jose Viña. "Antioxidant supplements in exercise: worse than useless?." American Journal of Physiology-Endocrinology and Metabolism 302.4 (2012): E476-E477.
- Holloszy, J. O., et al. "Response to letter to the editor by Gomez-Cabrera et al." American Journal of Physiology Endocrinology and Metabolism 302 (2012): E478-E479.
- Jówko, Ewa, et al. "The effect of green tea extract supplementation on exercise-induced oxidative stress parameters in male sprinters." European Journal of Nutrition (2014): 1-9.