Short-Term Mediterranean Dietary Intervention Reduces Plasma Trimethylamine-N-Oxide Levels in Healthy Individuals

<b>Objectives</b>: This study aimed to evaluate the association between adherence to the Mediterranean diet and blood trimethylamine-N-oxide (TMAO) levels. <b>Methods</b>: This randomized clinical trial enrolled 53 healthy adults with normal or overweight body mass index (BMI) who were recruited from a cardiology outpatient clinic in Istanbul, Turkey. Dietary patterns and Mediterranean diet adherence (assessed using the MEDAS) were evaluated alongside anthropometric and biochemical parameters, including fasting glucose, total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglycerides, alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Twenty individuals with low adherence underwent a 4-week Mediterranean dietary intervention with daily dietary monitoring. To assess changes, pre- and postintervention data were compared. <b>Results</b>: The results revealed that individuals adhering to the Mediterranean diet exhibited significantly lower blood TMAO levels (<i>p</i> < 0.001). In males, total cholesterol, LDL, triglyceride, and ALT levels significantly decreased compared with those at baseline (<i>p</i> < 0.05), whereas fasting blood glucose, HDL, and AST levels showed no significant changes (<i>p</i> > 0.05). In females, only blood TMAO levels exhibited significant reduction, with no other biochemical parameters indicating significant differences (<i>p</i> > 0.05). Additionally, males demonstrated significant improvements in anthropometric measures, including weight, BMI, fat mass, muscle mass, waist, and hip circumference, compared with pre-intervention values (<i>p</i> < 0.05), whereas females exhibited no significant changes in these measures (<i>p</i> > 0.05). <b>Conclusions</b>: Our findings demonstrate that implementing the Mediterranean diet in individuals with initially low adherence causes significantly reduced blood TMAO levels even within a short intervention period of 4 weeks.