The relationship between fish intake and urinary trimethylamine-N-oxide

Scope: Fish intake has been reported to associate with certain health benefits; however accurate assessment of fish intake is still problematic. The objective of this study was to identify fish intake biomarkers and examine relationships with health parameters in a free-living population. Methods and results: In the NutriTech study, 10 participants were randomised into the fish group and consumed increasing quantities of fish for 3 days/week during 3 weeks. Urine was analyzed by NMR-spectroscopy. Trimethylamine-N-oxide (TMAO), dimethylamine and dimethyl sulfone were identified and displayed significant dose response with intake (P < 0.05). Fish consumption yielded a greater increase in urinary TMAO compared to red meat. Biomarker derived fish intake was calculated in the National Adult Nutrition Survey (NANS) cross sectional study. However, the correlation between fish intake and TMAO (r=0.148, P < 0.01) and between fish intake and calculated fish intake (r=0.142, P < 0.01) were poor. In addition, TMAO showed significantly positive correlation with serum insulin and insulin resistance in males and the relationship was more pronounced for males with high dietary fat intake. Conclusion: Urinary TMAO displayed strong dose-response relationship with fish intake; however, use of TMAO alone is insufficient to determine fish intake in a free-living population.