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Published on: January 7, 2019
Effect of Green Tea Extract Supplementation on Substrate Utilization: A GRADE-Assessed Systematic Review and
Amir Hossein Khalilkhaneh1,2, Mohammad Vesal Bidsheki3,4, Salih M S Zebari5,6
1Sports Medicine Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran.
Context:
Several studies have assessed the effects of green tea extract (GTE) supplementation on substrate oxidation. However, no consensus has been reached due to the heterogeneity of the results, and so far no meta-analysis has been conducted on this topic.
Objective:
This systematic review and meta-analysis aimed to critically evaluate the effects of GTE supplementation on substrate oxidation, particularly on fat and carbohydrate oxidation during and after exercise.
Data Sources:
We conducted a comprehensive search of databases, including PubMed, Web of Science, and Scopus, to identify studies relevant to our research up until December 2024.
Data Extraction:
Eligible randomized controlled trials (RCTs) that reported relevant and adequate data about substrate oxidation were included in this meta-analysis. Also, we rated the evidence certainty using the 'Grading of Recommendations Assessment, Development and Evaluation' (GRADE) method.
Data Analysis:
Nine clinical trials evaluated the effect of GTE supplementation on substrate oxidation during and after exercise. In summary, intervention with GTE significantly increased fat oxidation both during (weighted mean difference [WMD]: 0.2 g/min; 95% CI; 0.04, 0.36; P = .016) and after exercise (WMD: 0.04 g/min; 95% CI; 0.01, 0.08; P = .023). Also, GTE significantly decreased carbohydrate oxidation after exercise (WMD: -0.16 g/min; 95% CI; -0.32, -0.01; P = .04) but did not significantly affect carbohydrate oxidation during exercise (WMD: -0.08 g/min; 95% CI; -0.29, 0.13; P = .468). Furthermore, the results of the dose-response analysis showed that an increase in the dose of GTE could augment fat oxidation after exercise (WMD: 0.03 g/min; 95% CI: 0.01, 0.06, P = .007). The quality of evidence was rated as low to high according to the GRADE criteria.
Conclusion:
Green tea extract supplementation significantly enhances fat oxidation during and after exercise, with limited effects on carbohydrate oxidation.
Systematic Review Registration:
PROSPERO registration No. CRD42024598165.
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