Current Evidence on Thiamin (Vitamin B1) Status in Healthy European Adults: A Systematic Review of Biomarkers and Deficiency Prevalence

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: A total of 19 cross-sectional studies from 11 countries, published between 1976 and 2024, met the inclusion criteria, providing data on 1687 individuals. The prevalence of thiamin deficiency (ETKAC >1.25, WB ThDP <70 nmol/L, total thiamin <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 %. Discussion: The prevalence of thiamin deficiency in Europe has not been reliably established owing to the lack of representative, population-based studies. Representative studies using harmonized thiamin biomarkers are urgently needed to establish the prevalence and public health significance of thiamin deficiency in Europe. Particular attention should be given to prevention of thiamin deficiency in high-risk groups, such as pregnant and lactating women, individuals following low-carbohydrate high-fat (LCHF) diets, and people with alcohol use disorder. Conclusions: It is commonly assumed that thiamin deficiency is not a problem in Europe, but the main finding of this systematic review is that there is virtually no representative data to support this assumption.