Nutrition knowledge, dietary practice and vitamin B12 levels in patients living with type 2 diabetes mellitus on metformin in Thulamela Municipality

Abstract

Background: Vitamin B12 deficiency is a recognized complication of long-term metformin use in patients with type 2 diabetes, yet data on its prevalence and dietary determinants in South African populations are limited. Objective: This study assessed the plasma vitamin B12 status and dietary intake of patients with type 2 diabetes receiving metformin in Thulamela Municipality, South Africa. Methods: A cross-sectional study was conducted among 339 patients. Socio-demographic data, anthropometric measurements, clinical history, and dietary intake were collected using structured questionnaires and 24-hour dietary recalls. Plasma vitamin B12 concentrations were measured using standard laboratory methods. Descriptive statistics, BMI classification, and Pearson correlation analyses were performed to examine associations between vitamin B12 status, dietary intake, and socio-demographic variables. Results: Among participants, 32.8% were vitamin B12 deficient, 35.7% had borderline levels, and 31.5% had normal concentrations. Overweight and obesity were prevalent, affecting 46.7% and 26.0% of participants, respectively. Dietary assessment showed high consumption of grains (100%), meat (95.3%), vegetables (87.6%), and fruits (83.5%), but lower intake of milk, eggs, seafood, legumes, and micronutrients such as folate, vitamin C, D, and E. Plasma vitamin B12 was positively associated with BMI, waist circumference, and employment status, and inversely associated with household income, while no significant correlations were observed with dietary diversity or nutrient intake. Conclusion: Vitamin B12 deficiency is common among metformin-treated patients with type 2 diabetes in Thulamela Municipality. Socio-demographic factors appear to influence vitamin B12 status more than dietary intake, highlighting the need for regular monitoring and potential supplementation in this population. Public health interventions should address both nutritional adequacy and the clinical management of diabetes.