INTRODUCTION

Oxidative stress is a condition resulting from an imbalance between the production of reactive oxygen species (ROS) and the capacity of the body's antioxidant defense system to neutralize them. Exercise, especially high-intensity, can temporarily increase ROS production in skeletal muscle and other tissues (through sources such as mitochondrial respiration, xanthine oxidase activity, and phagocyte activity), leading to transient oxidative stress. This increase in ROS can contribute to exercise-induced muscle damage and fatigue. However, there is strong evidence that regular exercise training and the resulting adaptations lead to improvements and strengthening of the body's endogenous antioxidant defense system. Meanwhile, garlic is recognized as one of the oldest medicinal plants, with a long history in traditional medicine and numerous health-promoting properties, including cardiovascular, anticancer, and immune system-modulating benefits. The potential interaction between regular exercise (as a chronic modulator of the antioxidant system) and garlic supplementation (as an exogenous antioxidant agent) on the body's oxidant/antioxidant status is not fully understood and requires further investigation. Most studies have either examined the effect of garlic alone or the acute effect of exercise combined with short-term supplementation; however, the combined effect of regular exercise training and long-term garlic supplementation has received less attention. Despite this biochemical basis and preliminary evidence, findings from randomized clinical trials (RCTs) on the effect of garlic supplementation on oxidative stress markers, particularly MDA and TAC, have been inconsistent. Therefore, considering the clinical importance of oxidative stress, the dual role of exercise, the antioxidant potential of garlic, and the inconsistencies in initial studies, the present study aimed to conduct a systematic review and meta-analysis of existing RCTs to determine the combined effect of regular exercise and garlic supplementation on malondialdehyde (MDA) levels and total antioxidant capacity (TAC).
METHODS
The present study is a systematic review and meta-analysis based on the Cochrane and PRISMA comprehensive guidelines. To extract articles, an advanced search was conducted in the PubMed, ScienceDirect, the Scientific Information Database (SID), Magiran, and Scopus databases, without a time limit until April 15, 2025, using the following keywords:
"Garlic," "Oxidative Stress," "Malondialdehyde," "Antioxidant Capacity," and "Exercise"
Statistical analysis of data was performed using Comprehensive Meta-Analysis (Version 2) software. In the present study, mean, standard deviation, and sample size were employed for statistical analysis. The I-square index was also used to determine the heterogeneity of the studies. The I² value is considered to be low heterogeneity (less than 25%), moderate heterogeneity (less than or equal to 50%), and high heterogeneity (more than 75%) based on the Cochrane test interpretation guidelines. In the present meta-analysis, the necessary criterion for heterogeneity was I² > 50% and p < 0.05; the mean difference and 95% confidence interval were also considered. Additionally, to quantitatively assess publication bias, funnel plots of effect size versus standard error were created, and funnel plot asymmetry was evaluated using the Egger test. The trim and fill method was also applied to eliminate publication bias.
RESULTS
In the initial search of articles identified in scientific databases, 1107 articles were extracted. Then, 589 articles were excluded after reviewing the title and abstract. After reviewing the full text of the articles, 91 articles were excluded due to a lack of experimental design, inadequate analysis, or the use of medication. A total of 10 studies that examined the role of exercise and garlic supplementation on oxidative stress index and TAC were meta-analyzed. The results of the meta-analysis demonstrated that garlic supplementation and exercise did not have a significant effect on MDA levels (ES=-0.50, 95% CI=-1.10 to 0.08, p=0.09) and TAC (ES=-0.50, 95% CI=-1.03 to 0.02, p=0.06).
CONCLUSION
The results of the present meta-analysis showed that the combination of regular exercise and garlic supplementation, despite the observed trends towards improving antioxidant status, did not have a statistically significant effect on MDA levels and TAC in the reviewed studies. This finding could be influenced by some factors, such as significant heterogeneity between studies in terms of garlic type and dose, exercise protocols, and study populations, the possible effect of improved antioxidant systems by exercise alone, and the relatively limited number of specific studies in this area. However, the results of some individual studies examining specific antioxidant enzymes are promising and indicate the need for further research with a more rigorous design, standardization of interventions (especially the type and dose of garlic product), and focus on more diverse markers to reach more definitive conclusions.

Ethical Considerations
Compliance with ethical guidelines
In this systematic review and meta-analysis, all ethical principles were observed, and no primary data were collected. Therefore, ethical approval and informed consent were not required.
Funding
There is no funding support.
Authors' Contributions
The authors contributed equally to the conceptualization and writing of the article.
All of the authors approved the content of the manuscript and agreed on all aspects of the work.
Conflict of Interest
The authors declared that there is no no conflict of interest.
Acknowledgments
Not applicable.