Riboflavin Deficiency Is Highly Prevalent in Females and Children across High and Low/Middle Income Countries Worldwide

BACKGROUND: Riboflavin, as flavin mononucleotide and flavin adenine dinucleotide, is essential for numerous metabolic pathways. However, the prevalence of riboflavin deficiency worldwide remains unclear, because status biomarkers are very rarely measured in human studies. OBJECTIVES: This study aimed to investigate riboflavin status in females of reproductive age and children from several regions of the world, representing both high-income countries and low/middle-income countries (HICs and LMICs). METHODS: We measured riboflavin status in population-representative samples from Ireland, United Kingdom, Cambodia, and Democratic Republic of the Congo, and in cohort samples from HICs (Northern Ireland, Spain, Canada) and LMICs (Malaysia, Lao People's Democratic Republic, Cambodia, Uganda) using the functional assay, erythrocyte glutathione reductase activation coefficient (EGRac), with higher values indicating lower status and EGRac ≥ 1.40 indicative of deficiency. RESULTS: In Irish (n = 251) and British (n = 163) populations, among unsupplemented females of 18-45 y, median (95% confidence interval) EGRac values were 1.39 (1.36, 1.42) and 1.40 (1.36, 1.49), and 48% and 50%, respectively, had riboflavin deficiency. In Irish females, biomarker status declined progressively(P < 0.002) with decreasing quintiles of dietary riboflavin intakes, from >2.1 in Q1 to