Vitamin D Supplementation, Total Testosterone, and Androgen Bioavailability Markers in Adult Men: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

What It Covers

Researchers studied Vitamin D, K2, Magnesium and Zinc in this meta-analysis publication.

This systematic review and meta-analysis evaluated the effects of vitamin D supplementation on total testosterone (TT) and androgen bioavailability markers in adult men, including sex hormone-binding globulin (SHBG), free androgen index (FAI), calculated free testosterone (calculated FT), and bioactive testosterone (BAT) where methodologically compatible.

Why It Was Studied

Vitamin D has traditionally been recognized for its role in calcium homeostasis and skeletal health, but vitamin D receptor expression and vitamin D-metabolizing enzymes have also been identified in extra-skeletal tissues, including components of the male reproductive tract.

Who the Included Studies Covered

The age groups tagged for this paper are adults, men only.

Embase was initially planned but was not searched because institutional access was unavailable; this amendment was made before screening, extraction, risk-of-bias assessment, and synthesis.

Meta-analyses used random-effects REML models with Hartung-Knapp adjustment.

How the Review Was Done

The review was registered in PROSPERO (CRD420261365005) and conducted according to PRISMA 2020 and Cochrane methodological guidance.

Searches were conducted from database inception to April 2026 in PubMed, Web of Science, Scopus, ClinicalTrials.gov, and the WHO ICTRP.

Records were deduplicated in Zotero, screened in a structured matrix, and converted from report-level records into independent comparison-level datasets where appropriate.

What Was Measured

PubMed files the paper under topics including Testosterone, Vitamin D, Androgens, Dietary Supplements, Randomized Controlled Trials as Topic, Biological Availability and Biomarkers.

The authors tagged it with the keywords androgen bioavailability, cholecalciferol, free androgen index, free testosterone, male hypogonadism and meta-analysis.

What This Means in Plain Language

This is a meta-analysis of Vitamin D, K2, Magnesium and Zinc.

Its findings take up roughly 9 sentences of the abstract and are left out here on purpose; the source paper is the place to read them.

The publication is from 2026 (Nutrients), a journal based in Switzerland.

More context: the Vitamin D, K2, Magnesium and Zinc compound page, all human trials.