Published in PLOS One on 2026-07-24, this study is presented as an attributed evidence briefing. The excerpts below are the original researchers’ words, reproduced under their Creative Commons Attribution licence. Health Signal has selected the abstract and, where needed, opening background paragraphs; the complete methods, results, limitations and references remain in the linked paper.
Original authors: Eyob Girma Abera, Samuel Alemu Himbaro, Surafel Worku Megersa, Tesfaye Adugna Leta, Ermias Habte Gebremichael, Akif Altınbas
Source: PLOS One • DOI 10.1371/journal.pone.0354518
Read the complete primary study ↗ · Creative Commons Attribution licence
From the researchers
Abstract
Type 2 diabetes mellitus (T2DM) has become a significant health challenge in Africa, with rapidly increasing prevalence. Despite abundant sunlight, vitamin D deficiency (VDD) is prevalent and may influence glucose metabolism and insulin resistance. Genetic factors, including vitamin D receptor (VDR) polymorphisms, may modify these effects. This systematic review and meta-analysis aimed to estimate the prevalence of VDD and evaluate the association of VDR gene variants with T2DM among African populations.
We systematically searched PubMed, Cochrane Library, ScienceDirect, Embase, Web of Science, and Google Scholar for observational studies published up to June 11, 2025, reporting VDD prevalence and VDR genetic associations in African individuals with T2DM. Data extraction and quality assessment followed Joanna Briggs Institute (JBI) and PRISMA 2020 guidelines. Pooled prevalence, mean difference and odds ratios (ORs) were calculated using random-effects meta-analysis. Heterogeneity, publication bias, sensitivity analyses, and meta-regression were performed. All statistical analyses were conducted using R version 4.3.1 (2023-06-16 ucrt).
Twenty-two eligible studies encompassing 3,447 participants from 11 African countries were included. The pooled prevalence of VDD among individuals with T2DM was 51% (95% CI: 36–65%), with substantial heterogeneity (I2 = 95.7%). Subgroup analyses showed highest prevalence in East Africa (56%). Vitamin D-deficient individuals had significantly higher HbA1c compared to sufficient individuals (mean difference = 0.89%; 95% CI: 0.06–1.72 p = 0.044; I2 = 0%, p = 0.49). The pooled analysis of VDR FokI polymorphisms did not demonstrate a significant association with T2DM risk (OR = 1.51; 95% CI: 0.23–9.73). No evidence of publication bias was detected.
Vitamin D deficiency is highly prevalent in African populations with T2DM and is associated with poorer glycemic control. Current evidence is insufficient to conclude on VDR FokI polymorphisms and T2DM risk. These findings underscore the need for interventional trials to determine whether improving vitamin D status enhances glycemic outcomes; routine screening or supplementation recommendations remain premature.
CRD420251134616.
Introduction
Type 2 diabetes mellitus (T2DM) has emerged as a significant public health concern in Africa, with its prevalence increasing rapidly across the continent. The International Diabetes Federation (IDF) reported that in 2021, approximately 24 million adults aged 20–79 years were living with diabetes in the African region, representing a prevalence of 4.5%. Alarmingly, more than half of these individuals remain undiagnosed, the highest proportion globally [1]. Projections indicate that the number of adults with diabetes in Africa will rise to 60 million by 2050, marking a 142% increase [2].
Recent evidence suggests a novel role of vitamin D in glucose homeostasis and insulin metabolism. Vitamin D modulates the immune system, regulates inflammatory cytokines, improves insulin secretion, and reduces insulin resistance. These mechanisms may influence the development and progression of T2DM [3]. In humans, the majority of vitamin D is synthesized in the skin upon exposure to ultraviolet B (UVB) radiation, while a smaller portion comes from dietary sources such as fatty fish, eggs, and fortified foods [4]. Serum 25-hydroxyvitamin D [25(OH)D] is the most reliable biomarker for assessing vitamin D status.
Reading this evidence
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This briefing makes the source accessible within the wider research & evidence desk. It does not assess an individual patient or certify a product. When considering relevance to another health system, examine the original authors’ account of context and limitations, then seek local implementation evidence. The related reporting below provides other studies to read alongside this one; it is a topic connection, rather than a claim that their results are directly comparable.
© 2026 Eyob Girma Abera, Samuel Alemu Himbaro, Surafel Worku Megersa, Tesfaye Adugna Leta, Ermias Habte Gebremichael, Akif Altınbas. Excerpts reproduced under CC BY. Selection, formatting and contextual notes by Health Signal. The researchers are the authors of the source study, not members of Health Signal’s staff.
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