Association between dietary thiamine intake and serum lipid profiles in U.S. adults: NHANES 2021–2023

Thiamine (vitamin B1) is an essential water-soluble vitamin involved in carbohydrate metabolism and energy production. Emerging evidence suggests that thiamin may influence lipid metabolism and cardiovascular risk, yet population-based data are limited and inconsistent. This study aimed to investigate the association between dietary thiamin intake and serum lipid profiles, including total cholesterol, LDL-C, HDL-C, and triglycerides, among U.S. adults. Data from 4986 fasting adults aged ≥ 18 years from the National Health and Nutrition Examination Survey (NHANES) 2021 to 2023 were analyzed. Dietary thiamin intake was assessed using the first 24-hour dietary recall and classified into four intake categories based on the distribution of thiamin intake. Linear regression models were used to examine the associations between dietary thiamin intake and serum lipid components, with sequential adjustment for demographic, socioeconomic, lifestyle, dietary, and health-related factors. A sensitivity analysis was additionally performed, adjusting for lipid-lowering medication use. In fully adjusted models, higher thiamin intake was associated with lower total cholesterol (β = -7.13, SE = 2.61, P = .007) and LDL-C (β = -6.72, SE = 3.27, P = .04). No significant associations were observed with HDL-C (β = -0.21, SE = 0.80, P = .79) or triglycerides (β = 13.82, SE = 10.37, P = .183). In the sensitivity analysis additionally adjusted for lipid-lowering medication use, the associations with total cholesterol and LDL-C remained significant, while those with HDL-C and triglycerides remained nonsignificant. These findings indicate an inverse association between dietary thiamin intake and selected atherogenic lipid fractions. Among U.S. adults, higher dietary thiamin intake is associated with lower total and LDL cholesterol levels. Higher thiamin intake may be associated with a more favorable lipid profile and may represent a potential dietary factor relevant to cardiovascular risk management. Given the cross-sectional design, causal relationships cannot be inferred, and further prospective and interventional studies are warranted to confirm these findings and elucidate underlying mechanisms.