Associations of Salivary Microbiota with Diet Quality, Body Mass Index, and Oral Health Status in Turkish Adolescents

<b>Background:</b> The oral microbiota is the largest and most diverse microbial community in the human body, shaped by numerous factors such as body composition, dietary habits, and oral health status. However, relationships between these parameters and the salivary microbiota in adolescents are not yet well understood. <b>Objectives:</b> This study aimed to characterize the salivary microbiota of healthy Turkish adolescents and to examine its associations with body mass index (BMI), diet quality, decayed-missing filled teeth (DMFT) index, and community periodontal index of treatment needs (CPITN). <b>Methods:</b> A descriptive, cross-sectional study was conducted among 40 adolescents aged 14-18 years, classified into four BMI z-score categories (underweight, normal weight, overweight, and obese). Anthropometric measurements, nutritional information, and oral health parameters (DMFT, CPITN) were assessed. Unstimulated saliva samples were collected, and the V3-V4 region of the 16S rRNA gene was sequenced using Illumina MiSeq. Alpha and beta diversity, differential abundance (LEfSe), and correlations with HEI components were analyzed. <b>Results:</b> Underweight adolescents exhibited significantly higher alpha diversity than obese participants (<i>p</i> = 0.024), while beta diversity did not differ across BMI, HEI, DMFT, or CPITN categories. LEfSe analysis revealed BMI-specific taxa: <i>Leptotrichia</i> sp., <i>Haemophilus</i> sp., and <i>Treponema socranskii</i> were enriched in the underweight group; <i>Prevotella denticola</i> in the obese group; and <i>Selenomonas sputigena</i> in the normal-weight group. HEI components, including whole fruits, whole grains, and plant-based proteins, showed positive correlations with <i>Desulfobacterota</i> and <i>Proteobacteria</i>. Poor oral hygiene was associated with higher species richness but not with large shifts in community structure. <b>Conclusions:</b> Salivary microbiota diversity and composition in adolescents vary with BMI, diet quality, and oral hygiene. These patterns are consistent with the idea that targeted nutritional and oral health interventions could influence the salivary microbiome during adolescence.