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Effects of Vitamin D Supplementation on Inflammatory Markers in Athletic and Trained Populations: A Systematic Review and Narrative Synthesis of Randomized Controlled Trials
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M.N Goli Eskardi    , A.H Razipour Juybari , A Gholamalizade , A Hekmatdoost * |
| Department of Clinical Nutrition & Dietetics, Faculty of Nutrition and Food Industries, National Nutrition and Food Industries Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran , a_hekmat2000@yahoo.com |
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Abstract: (29 Views) |
Background and Objectives: Strenuous exercise can trigger an acute inflammatory response which, if excessive or prolonged, may impair recovery and athletic performance. Given the immunomodulatory role of vitamin D, this systematic review aimed to evaluate the effects of vitamin D supplementation on exercise-induced inflammatory biomarkers in athletic and trained populations.
Materials & Methods: This review was conducted in accordance with the Cochrane Handbook and the PRISMA 2020 statement. Randomized controlled trials (RCTs) enrolling athletes or trained individuals were included. Outcomes comprised a range of cytokines and inflammatory biomarkers. Risk of bias was assessed using the RoB 2 tool. Due to substantial heterogeneity across studies, results were synthesized using a Synthesis Without Meta-analysis (SWiM) approach, based on direction of effect and combined p values.
Results: Of 1,474 records identified, seven trials (n = 209 participants) met the inclusion criteria. Overall, vitamin D supplementation was associated with a favorable direction of change in some inflammatory outcomes. More consistent beneficial findings were reported for IL-6, TNF-α, and selected related markers, whereas results for CRP and hs-CRP were heterogeneous and largely non-significant. Most RoB 2 domains were judged as low risk of bias; however, several studies raised “some concerns,” mainly related to the selection of the reported outcomes.
Conclusion: This review suggests that vitamin D supplementation may, under certain conditions, be associated with modulation of selected inflammatory biomarkers in athletic and trained populations. Nonetheless, clinical and methodological heterogeneity, along with the limited number of available RCTs, restricts definitive inference. Therefore, these findings should be interpreted with caution. |
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| Keywords: Vitamin D, Inflammation, Exercise training, Systematic review, Narrative synthesis |
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Full-Text [PDF 856 kb]
(16 Downloads)
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Article type: Review |
Subject:
nutrition
Received: 2026/01/5 | Accepted: 2026/06/30
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