The researchers analyzed riboflavin (vitamin B2) status in 3,567 participants from 17 cohorts in nine countries across Europe, North America, Asia and Africa.
“This study is a first step in providing evidence to underpin emerging dietary recommendations and food policy measures concerning riboflavin,” they wrote.
Riboflavin deficiency impacts metabolism, iron and vitamin B6 levels
Riboflavin is necessary as the body converts it into the cofactors FMN and FAD, which support many metabolic processes. These cofactors transfer protons in oxidation–reduction reactions, help generate energy through the mitochondrial electron transport chain, and assist enzymes in metabolizing drugs and toxins.
Riboflavin also supports iron metabolism and helps release stored iron from ferritin, meaning riboflavin supplementation can improve hematological responses beyond iron supplementation alone and may help prevent anemia, particularly in women of reproductive age.
Furthermore, it plays a critical role in folate and one-carbon metabolism by enabling the enzyme MTHFR to function. In addition, riboflavin helps convert vitamin B6 into its active form (PLP), making riboflavin status an important determinant of vitamin B6 levels.
Because riboflavin supports multiple metabolic pathways, deficiency can disrupt the metabolism of other nutrients. However, estimates suggest that more than 4 billion people worldwide consume insufficient riboflavin.
The researchers noted that global riboflavin status remains unclear because many studies do not measure riboflavin biomarkers. They therefore used the erythrocyte glutathione reductase activation coefficient (EGRac) assay method, a test that measures how strongly enzyme activity depends on riboflavin and identifies deficiency.
Women at higher risk of riboflavin deficiency than men
The researchers collected venous blood samples and assessed riboflavin status using the EGRac assay. In Irish and UK cohorts, researchers also collected dietary intake data using four-day semi-weighed food diaries, evaluating riboflavin intake using established dietary reference values.
Across both Ireland and the UK, women had lower riboflavin intake and poorer riboflavin status than men. In Ireland, women consumed a median of 1.6 mg/day compared with 2.4 mg/day in men. In addition, 34% of women consumed less than the average requirement compared with 9% of men. Nearly half of Irish women who did not consume supplements were riboflavin deficient, and similar patterns appeared in the UK.
Globally, riboflavin deficiency was widespread. Among women in high-income countries such as Canada, about 45% were deficient. In low- and middle-income countries, deficiency rates were much higher, with 72% of women deficient in Malaysia, 82% in Cambodia and 90% in Uganda.
Among children, riboflavin status declined with age in the UK, with deficiency rates ranging from 19% in children aged one to five, to over 50% in teenagers. Meanwhile, children in low- and middle-income countries showed deficiency rates as high as 75%.
“The current study draws on two population-based cohorts (from Ireland and the UK) to link dietary intakes with corresponding riboflavin biomarker values, and the results show that females are at particular risk both of dietary insufficiency and low/deficient status,” wrote the researchers.
“Given the adverse health consequences of deficiency, population-based strategies to improve riboflavin status in both LMICs and HICs are needed.”
They added that future research should investigate the effects of interventions aimed at improving riboflavin status and preventing the clinical sequelae of riboflavin deficiency.
Source: The Journal of Nutrition; doi: https://doi.org/10.1016/j.tjnut.2025.101277; “Riboflavin Deficiency Is Highly Prevalent in Females and Children across High and Low/Middle Income Countries Worldwide.” Authors: McAnena, L. et al.
