Objectives: The aim of this study was to investigate the effects of green tea catechins (GTC) on oxidative stress metabolites in healthy individuals while at rest and during exercise. The effects investigated included response to fat metabolism, blood lactate concentrations, and rating of perceived exertion.
Methods: In a paralleled, crossover, randomized controlled study, 16 trained male gymnastic students were randomly divided into two groups. The rest group (n = 8; GTC-NEX) received a single dose of 780 mg GTC with water but no exercise; the exercise group (n = 8; GTC-EX) received a similar dose of GTC but were instructed to exercise. This was followed by a crossover study with similar exercise regime as a placebo group (PL-EX) that received water only. Blood samples were collected at baseline and after 60 and 120 min of GTC intake. Oxidative stress blood biomarkers using the diacron reactive oxygen metabolite (d-ROMs) and biological antioxidant potential (BAP) tests; urinary 8-hydroxydeoxyguanosine (8-OHdG); 8-OHdG/creatinine; and blood lactate concentrations were analyzed. During the cycle ergometer exercise, volume of maximal oxygen uptake, volume of oxygen consumption, volume of carbon dioxide, and respiratory exchange ratio were measured from a sample of respiratory breath gas collected during low, moderate, and high intensity exercising, and the amount of fat burning and sugar consumption were calculated. Analysis of variance was used to determine statistical significance (P < 0.05) between and among the groups.
Results: Levels of postexercise oxidative stress metabolites BAP and d-ROMs were found significant (P < 0.0001) in the PL-EX and GTC-EX groups, and returned to pre-exercise levels after the recovery period. Levels of d-ROMs showed no significant difference from baseline upon GTC intake followed by resting and a resting recovery period in the GTC-NEX group. BAP levels were significant upon GTC intake followed by resting (P = 0.04), and after a resting recovery period (P = 0.0006) in the GTC-NEX group. Urinary 8-OHdG levels were significant (P < 0.005) for all groups after the recovery period. A significant difference was noticed between the ratios of resting BAP to d-ROMs and exercise-induced BAP to d-ROMs (P = 0.022) after 60 min of GTC intake, as well as resting 8-OHdG and exercise-induced 8-OHdG levels (P = 0.004) after the recovery period. Oxidative potentials were higher when exercise was performed at low to moderate intensity, accompanied by lower blood lactate concentration and higher amounts of fat oxidation.
Conclusions: The results of the present study indicate that single-dose consumption of GTC influences oxidative stress biomarkers when compared between the GTC-NEX and GTC-EX groups, which could be beneficial for oxidative metabolism at rest and during exercise, possibly through the catechol-O-methyltransferase mechanism that is most often cited in previous studies.
Keywords: Antioxidant; Catechins; Exercise; Green tea; Stress metabolites.
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