Can molecular hydrogen supplementation reduce exercise-induced oxidative stress in healthy adults? A systematic review and meta-analysis.

Abstract

<h4>Objective</h4>Exercise-induced oxidative stress affects multiple neurophysiological processes, diminishing the exercise performance. Hydrogen (H₂) can selectively reduce excessive free radicals, but studies observed its "dual effects" on exercise-induced oxidative stress, that is, increasing or decreasing the oxidative stress. Therefore, we here conducted a systematic review and meta-analysis to quantitatively assess the influence of H₂ on exercise-induced oxidative stress in healthy adults.<h4>Methods</h4>We conducted a systematic review of publications across five databases. The following keywords were used for search strategy: ["hydrogen"[Mesh] or "molecular hydrogen" or "hydrogen rich water" or "hydrogen-rich water" or "hydrogen rich saline"] and ["Oxidative Stress"[Mesh] or "Antioxidative Stress" or "Oxidative Damage" or "Oxidative Injury" or "Oxidative Cleavage"] and ["randomized controlled trial"[Mesh] or "randomized" or "RCT"]. We included trials reporting the effects of H₂ on exercise-induced oxidative stress and potential antioxidant capacity post-exercise in healthy adults. Additionally, subgroup analyses were conducted to explore how various elements of the intervention design affected those outcomes.<h4>Results</h4>Six studies, encompassing seven experiments with a total of 76 participants, were included in our analysis. Among these studies, hydrogen-rich water, hydrogen bathing, and hydrogen-rich gas were three forms used in H₂ administration. The H₂ was applied in different timing, including before, during, or after exercise only, both before and after exercise, and repeatedly over days. Single-dose, multi-dose within 1 day and/or multiple-dose over days were implemented. It was observed that compared to placebo, the effects of H₂ on oxidative stress (diacron-reactive oxygen metabolites, d-ROMs) was not significant (SMD = -0.01, 95%CI-0.42 to 0.39, <i>p</i> = 0.94). However, H₂ induced greater improvement in antioxidant potential capacity (Biological Antioxidant Potential, BAP) (SMD = 0.29, 95% CI 0.04 to 0.54, <i>p</i> = 0.03) as compared to placebo. Subgroup analyses revealed that H₂ supplementation showed greater improvement (SMD = 0.52, 95%CI 0.16 to 0.87, <i>p</i> = 0.02) in the antioxidant potential capacity of intermittent exercises than continuous exercise.<h4>Conclusion</h4>H₂ supplementation can help enhance antioxidant potential capacity in healthy adults, especially in intermittent exercise, but not directly diminish the levels of exercise-induced oxidative stress. Future studies with more rigorous design are needed to examine and confirm these findings.<h4>Systematic review registration</h4>https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=364123, Identifier CRD42022364123.