2024 · Li et al. — Can Molecular Hydrogen Supplementation Reduce Exercise-Induced Oxidative Stress in Healthy Adults? A Systematic Review and Meta-Analysis
Super-Abstract
Across six studies with 76 healthy adults, hydrogen did not lower the exercise-induced oxidative stress marker d-ROMs compared with placebo (SMD −0.01, p = 0.94), but it raised the antioxidant capacity marker BAP by a small amount (SMD 0.29, p = 0.03). In a subgroup analysis, the gain in BAP was reported as larger with intermittent than with continuous exercise (SMD 0.52). The included studies gave hydrogen as hydrogen-rich water, hydrogen baths or hydrogen-rich gas, at different times and doses. With 76 participants in total and no heterogeneity figures in the abstract, the results are imprecise. (Frontiers in Nutrition, 2024.)
Commentary
Hydrogen is thought to reduce excess free radicals selectively, but earlier studies reported both increases and decreases in exercise-induced oxidative stress. This systematic review, registered in PROSPERO (CRD42022364123), searched five databases with terms for hydrogen, oxidative stress and randomised trials. The abstract does not give the search date. It included trials in healthy adults that reported effects of hydrogen on oxidative stress and antioxidant capacity after exercise. Six studies with seven experiments and 76 participants were analysed. Hydrogen was given as hydrogen-rich water, hydrogen baths or hydrogen-rich gas, before, during or after exercise, or repeatedly over several days, as single or multiple doses. The main outcomes were diacron-reactive oxygen metabolites (d-ROMs) as a marker of oxidative stress and biological antioxidant potential (BAP) as a marker of antioxidant capacity, each compared with placebo. Subgroup analyses examined elements of the intervention design.
Key quotes
- „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, p = 0.94).“ — the main oxidative stress marker showed no difference from placebo
- „However, H2 induced greater improvement in antioxidant potential capacity (Biological Antioxidant Potential, BAP) (SMD = 0.29, 95% CI 0.04 to 0.54, p = 0.03) as compared to placebo.“ — the positive finding: a small effect, with the lower confidence limit near zero
- „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.“ — the authors' conclusion, which names both the positive and the null result
Our assessment
This small meta-analysis gives a split answer. Hydrogen did not lower the oxidative stress marker d-ROMs after exercise. It raised the antioxidant marker BAP slightly, with a confidence interval whose lower limit (0.04) lies close to zero. Both are blood markers, so the review says nothing directly about performance, recovery or health. Limitations: only six studies with 76 participants were included. Three different forms of hydrogen with different timing and dosing were pooled. The abstract reports no heterogeneity statistics, no risk-of-bias assessment and no certainty rating, and it does not give the search date. The intermittent-exercise subgroup rests on even fewer data and is best read as a hypothesis. The authors themselves call for more rigorous studies to confirm the findings.
Study design
- Type: systematic review and meta-analysis, registered in PROSPERO (five databases, search date not stated in the abstract) · n: 76 healthy adults in six studies (seven experiments) · H₂ delivery: hydrogen-rich water, hydrogen baths or hydrogen-rich gas, single or repeated doses before, during or after exercise
- Included studies: trials in healthy adults, found with a search restricted to randomised designs, that reported oxidative stress and antioxidant capacity after exercise, hydrogen compared with placebo
- Result: d-ROMs SMD −0.01 (95% CI −0.42 to 0.39, p = 0.94), not significant. BAP SMD 0.29 (95% CI 0.04 to 0.54, p = 0.03). Subgroup with intermittent exercise, reported as a greater BAP improvement than with continuous exercise: SMD 0.52 (95% CI 0.16 to 0.87, p = 0.02)
Abstract
OBJECTIVE: 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. METHODS: 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. RESULTS: 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, p = 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, p = 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, p = 0.02) in the antioxidant potential capacity of intermittent exercises than continuous exercise. CONCLUSION: 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. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=364123, Identifier CRD42022364123.
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