{
  "abstract": "Background/Objectives: Vitamin D plays an important role in bone and muscle health; however, whether supplementation improves physical performance in combat-sport athletes remains unclear. This review examined randomized placebo-controlled trials of oral vitamin D supplementation and objective physical-performance outcomes in healthy combat-sport athletes. Methods: PubMed, Scopus, and the Cochrane Library were searched from inception to 22 January 2026, with supplementary targeted verification searches conducted through 1 September 2026. Trials were eligible when combat-sport athletes were randomized to receive vitamin D or placebo/no vitamin D and objective physical performance was assessed. Two reviewers independently performed study selection, data extraction, and risk-of-bias assessment. Findings were synthesized narratively by prioritizing randomized between-group contrasts, group-by-time interactions, numerical changes, and reported effect sizes. Results: Four trials were included, involving 108 randomized participants and 99 analyzed observations. Individual trials reported statistically significant group-by-time effects for selected measures of isokinetic torque, Wingate peak power, high-velocity knee-extension torque, lower-body peak oxygen uptake, handgrip strength, isometric press-up endurance, and lower-body best repeated-sprint peak power. Published standardized effect-size estimates were available for several selected outcomes; however, confidence intervals for between-group effects were generally unavailable. Related outcomes, including Wingate mean or average power, other torque velocities, upper-body peak oxygen uptake, time to exhaustion, oxygen kinetics, wall-sit endurance, and most repeated-sprint measures, showed no statistically significant between-group interaction. No trial assessed competition performance, and all trials presented at least some risk-of-bias concerns. Conclusions: Individual trials reported statistically significant effects on selected laboratory measures. However, the available evidence is not sufficient to determine whether vitamin D supplementation meaningfully improves physical or sport-specific performance in combat-sport athletes. Correcting low vitamin D status should be distinguished from supplementation for performance enhancement. Further well-designed trials are required.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Life Sciences, School of Life and Health Sciences, University of Nicosia, Nicosia 2417, Cyprus",
    "Research Centre for Exercise and Nutrition (RECEN), University of Nicosia, Nicosia 2417, Cyprus"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 5,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Marinos Michael"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Christoforos D. Giannaki",
      "orcid": "0000-0003-0029-1189"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Pinelopi S. Stavrinou",
      "orcid": "0000-0003-2904-3218"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Eleni Andreou",
      "orcid": "0000-0002-0449-6782"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Angelos Vlahoyiannis",
      "orcid": "0000-0001-8424-3314"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/fhrktqjb7et8n.bib",
  "cited_by": 0,
  "doi": "10.3390/nu18213547",
  "fulltext_url": null,
  "id": "fhrktqjb7et8n",
  "issns": [
    "2072-6643"
  ],
  "landing_url": "https://www.mdpi.com/2072-6643/18/21/3547",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "2734|Vitamin D Research Studies"
    ]
  ],
  "openalex": "W7224105631",
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-28",
  "publisher": "MDPI AG",
  "ris": "https://research.draconitic.com/paper/fhrktqjb7et8n.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:19:56Z",
      "native_id": "10.3390/nu18213547",
      "source": "crossref",
      "url": "https://www.mdpi.com/2072-6643/18/21/3547"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "issn:2072-6643",
      "subfield": "nutrition"
    }
  ],
  "title": "Effects of Oral Vitamin D Supplementation on Physical Performance in Combat-Sport Athletes: A Systematic Review of Randomized Placebo-Controlled Trials",
  "title_text": "Effects of Oral Vitamin D Supplementation on Physical Performance in Combat-Sport Athletes: A Systematic Review of Randomized Placebo-Controlled Trials",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:19:56Z",
  "url": "https://research.draconitic.com/paper/fhrktqjb7et8n",
  "venue": "Nutrients",
  "versions": []
}