Current evidence on thiamin (vitamin B1) status in healthy European adults: a systematic review of deficiency prevalence

Abstract Objective This systematic review evaluates the thiamin status of the European adult population, identifying critical gaps and priorities for future research. Methods The review was conducted according to a pre-registered protocol (PROSPERO: CRD420251101630) and PRISMA guidelines. A systematic search of PubMed and Scopus was carried out to identify observational studies reporting relevant thiamin status biomarkers (erythrocyte transketolase activity coefficient (ETKAC), whole blood thiamin diphosphate (WB ThDP), total thiamin in whole blood, or erythrocyte thiamin diphosphate - RBC ThDP) in apparently healthy, community-dwelling adults (≥ 18 years) from European countries. Results and discussion A total of 21 cross-sectional studies from 11 countries, published between 1976 and 2026, met the inclusion criteria, providing data on 7,344 individuals. The prevalence of thiamin deficiency (ETKAC > 1.25, WB ThDP < 70 nmol/L, total thiamin in whole blood < 75 nmol/L, RBC ThDP < 280 ng/g Hb) ranged from 0% to 41.2%. When pregnant and post-partum women were excluded, the prevalence of thiamin deficiency ranged from 0% to 10%. The prevalence of thiamin deficiency in Europe remains poorly established because nationally representative studies in the general population are scarce. The largest and most recent data come from the United Kingdom, where wheat flour is fortified with thiamin. Conclusions Further population-based studies using harmonised biomarkers are required before reliable conclusions can be drawn regarding the prevalence and public health significance of thiamin deficiency in Europe.