Effect of Green Tea Supplementation on Antioxidant Status in Adults: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Abstract

It is well-established that green tea supplementation has antioxidant properties. However, whether green tea supplementation leads to oxidative stress reduction remains unclear, as clinical investigations on this subject have yielded inconsistent outcomes. Consequently, we aimed to determine the effects of green tea supplementation on oxidative stress in adults. A systematic search of English language publications up to 21 August 2021 was carried out in PubMed, Scopus, Embase, and ISI Web of Science, utilizing pertinent keywords. These searches included randomized controlled trials (RCTs) evaluating the relationship between green tea supplementation, malondialdehyde (MDA), and total antioxidant capacity (TAC) in adults. A random-effects model was used to estimate the weighted mean difference (WMD) and 95% confidence intervals (95% CI). Meta-regression and non-linear dose-response analyses were performed to investigate the association between the dosage of green tea (mg/day) and the duration of the intervention (weeks) with pooled effect size. Sixteen RCTs with seventeen arms including 760 participants met the inclusion criteria. Our results indicated that green tea supplementation had significant effects on TAC (weighted mean difference [WMD]: 0.20 mmol/L; 95% CI: 0.09, 0.30, p < 0.001) and significant heterogeneity between studies (I2 = 98.6%, p < 0.001), which was largely related to gender and body mass index (BMI). Subgroup analysis in TAC identified a significant relationship except with low dose supplementation and obese individuals. No relationship between MDA and green tea supplementation was observed in any subgroups; however, meta-regression analysis revealed a linear inverse association between the dosage and significant change in MDA (r = −2117.18, p = 0.017). Our outcomes suggest that green tea supplementation improves TAC and affects MDA based on the dose of the intervention in adults. Future RCTs with longer durations are needed to expand our findings.

The effects of green tea extract supplementation on body composition, obesity-related hormones and oxidative stress markers: a grade-assessed systematic review and dose–response meta-analysis of randomised controlled trials

“…In the subgroup analysis, a greater increase in TAC was revealed in studies conducted on men, but only a study among women showed a significant reduction in MDA. Our recent meta-analysis on the antioxidant effects of supplementing with all types of green tea demonstrated beneficial effects on TAC in adults; however, in contrast to our results, no reduction in MDA was observed except for low-dose supplementation and individuals with obesity (31) . Although it is becoming increasingly evident that GTE supplementation has a potential role in enhancing TAC (70,71,128) , its effects on MDA as a lipid peroxidation indicator have yet to be established.…”

“…Prior meta-analytic works by Rasaei et al (31) and Lin et al (106) reported the effects of GTE supplementation on antioxidant status and obesity, respectively. The present findings exhibit discrepancies with the results of these two recently published meta-analyses, which provided new knowledge on several relevant topics.…”

“…In contrast, our study revealed decreased C-reactive protein and malondialdehyde (MDA) in type 2 diabetes mellitus patients following GTE supplementation (30) . Our most recent study indicated that GTE supplementation significantly increased total antioxidant capacity (TAC); moreover, meta-regression analysis revealed a linear inverse association between the dosage and significant change in MDA (31) . Moreover, while some studies reported that GTE supplementation improves body fatness or mass in individuals with obesity (32–34) , some studies did not find any favourable effects (35,36) .…”

Antioxidant and Anti-Inflammatory Compounds from Edible Plants with Anti-Cancer Activity and Their Potential Use as Drugs

“…This is because cancer cells have redox regulation genes, suggesting that low ROS levels are required for their survival; however, the therapeutic approach may be crucial to treating this pathology. Nevertheless, in clinical trials has been shown that antioxidant consumption might be beneficial [ 167 , 168 , 169 , 170 , 171 , 172 ] or have no effect [ 167 , 172 , 173 , 174 ], as it is suggested to depend on the metabolic demand of the individual.…”

Mental Performance and Sport: Caffeine and Co-consumed Bioactive Ingredients

“…It also contains the tea-specific amino-acid ʟ-theanine and caffeine. Meta-analyses of controlled trial data show that the consumption of green tea extracts is associated with a number of cardiovascular and anthropomorphic benefits, including enhanced total antioxidant status [ 162 ], improved glucoregulation [ 163 ] and significant benefits to weight, BMI and waist circumference, irrespective of caffeine content [ 164 ]. Whilst the exercise performance effects of green tea extracts remain unclear, consumption of caffeinated green tea extracts for more than 1 week has been shown to reduce exercise-induced oxidative stress [ 165 ].…”