The health outcomes of vitamin D supplementation in Africa: a systematic review and meta-analysis

BackgroundVitamin D supplementation is essential for health, yet its full benefits and optimal use remain incompletely understood, particularly given the global prevalence of deficiency, which affects around 50% of the population, with higher rates in high-latitude regions and among individuals with darker skin. This systematic review synthesizes evidence on the health outcomes of vitamin D supplementation in Africa, addressing gaps in regional and demographic-specific research.MethodsA comprehensive literature search was conducted using PubMed, Scopus, Epistemonikos, and Google Scholar, limited to English-language publications without date restrictions. Two independent reviewers evaluated study eligibility, data quality, and risk of bias. The findings were reported in accordance with PRISMA guidelines, employing narrative synthesis and meta-analyses to compare the effects of vitamin D supplementation against control groups. Heterogeneity and publication bias were assessed using Egger's regression and Q statistics.ResultsThe review included 14 randomized controlled trials from 9 African countries, involving 11,259 participants. Half of the studies reported health benefits associated with vitamin D supplementation. Meta-analysis of seven studies demonstrated significant increases in serum vitamin D levels (odds ratio = 6.78, p < 0.001) and reduced viral load in patients with human immunodeficiency virus (odds ratio = 1.63, p = 0.033). However, supplementation did not significantly affect weight gain (odds ratio = 1.1, p = 0.18) or mortality rates in patients with tuberculosis and human immunodeficiency virus (odds ratio = 0.971, p = 0.638). Improvements in disease symptoms and biochemical markers were observed (odds ratio = 2.28, p = 0.028), with no significant heterogeneity or publication bias. Subgroup analysis was constrained by the diversity of diseases and insufficient studies.ConclusionsVitamin D supplementation showed significant benefits in half of the studies, elevating serum levels and reducing viral load in HIV patients. However, it did not affect weight gain or mortality in TB and HIV patients. While symptom and biomarker improvements were noted, further research is needed to explore subgroup effects and optimize strategies.Trial registrationPROSPERO registration number CRD42024620729.