Vitamin Status of Adults with Type 2 Diabetes in Africa: A Scoping Review

Type 2 diabetes mellitus (T2DM) represents one of the most rapidly growing public health crises on the African continent. According to the International Diabetes Federation (IDF 2025), Africa currently accounts for over 24 million adults living with diabetes, a figure projected to nearly double by 2045, the fastest growth rate of any region globally. This epidemiological burden is compounded by widespread nutritional vulnerabilities specific to African populations, including dietary deficiencies in vitamins essential to glucose metabolism, insulin signaling, and the prevention of diabetic complications. Vitamins play critical and mechanistically distinct roles in the pathophysiology of T2DM. Vitamin D modulates pancreatic beta-cell function and insulin sensitivity through the vitamin D receptor expressed on beta cells and peripheral tissues. B-group vitamins, particularly vitamin B12, folate (B9), and vitamin B6 ,are implicated in homocysteine metabolism, the risk of diabetic peripheral neuropathy, and the integrity of one-carbon metabolic pathways. Metformin, the most widely prescribed first-line antidiabetic agent in Africa, is well documented to impair vitamin B12 absorption through competitive inhibition of the intrinsic factor-B12 receptor complex in the ileum, raising the risk of subclinical B12 deficiency in treated patients. Vitamins C and E exert antioxidant effects directly relevant to the chronic oxidative stress characteristic of T2DM. Vitamin A participates in insulin gene expression and retinol-binding protein signaling pathways that intersect with insulin resistance. Despite this well-established pathophysiological relevance, and despite the recognized burden of malnutrition and food insecurity across many African countries, no scoping review has to date systematically mapped the available evidence on the vitamin status of adults with T2DM living in Africa. Existing literature is fragmented across individual country studies, limited to single vitamins (most frequently vitamin D), or embedded in broader reviews on micronutrients that encompass minerals and trace elements alongside vitamins without differentiating their specific contributions. No synthesis exists that covers the full vitamin spectrum; vitamins A, B1, B2, B3, B6, B9/folate, B12, C, D, E, and K, in a T2DM population specifically located on the African continent. This scoping review aims to fill this evidence gap. Conducted according to the five-step framework of Arksey and O'Malley (2005), revised by Levac et al. (2010) and formalized in the JBI Manual for Evidence Synthesis (Peters et al., 2020), and reported following the PRISMA-ScR guidelines (Tricco et al., 2018), it will systematically search eight databases : PubMed/MEDLINE, Scopus, Web of Science, Embase, CINAHL, Cochrane Library, AJOL (African Journals Online), and Google Scholar from inception to the search date, with no language or date restrictions. The primary research question is: What is the vitamin status of adults with type 2 diabetes mellitus living in Africa, which vitamins are most frequently studied and deficient, and what associations exist between vitamin status and glycemic parameters? Secondary objectives are: (1) to identify the vitamins most frequently studied and most commonly deficient in this population; (2) to characterize the geographical distribution of studies across African regions and countries; (3) to describe the methods used to assess vitamin status; (4) to examine reported associations between vitamin status and HbA1c, fasting plasma glucose, and insulin resistance indices. Eligibility will follow the PCC framework: - Population : adults ≥18 years with confirmed T2DM in any African country; - Concept : status of any vitamin (A, B-group, C, D, E, or K) assessed by serum, plasma, dietary, urinary, or erythrocyte measurement; - Context : all African countries. All study designs are eligible. Expected outcomes include: a comprehensive map of the available evidence on vitamin status in T2DM adults across Africa; identification of the most prevalent vitamin deficiencies and the vitamins least studied in this population; a synthesis of reported associations between vitamin status and glycemic control and characterization of the African countries and regions best and least represented in the literature. This review is expected to provide the first systematic evidence base to inform nutritional assessment protocols for T2DM patients in African clinical settings, and to support the development of context-adapted dietary guidelines for this population.