Gut Microbiota: Association with Fiber Intake, Ultra-Processed Food Consumption, Sex, Body Mass Index, and Socioeconomic Status in Medical Students

Abstract

The gut microbiota plays a vital role in various physical and physiological processes, including immune system regulation, neurotransmitter production, inflammatory response modulation, and the inhibition of pathogenic organisms. An imbalance in the microbial community, known as dysbiosis, has been associated with numerous health issues. Biological influences, health behaviors, socioeconomic determinants, and nutritional status can disrupt this balance.

Objective: To evaluate the differences in the gut microbiota composition in medical students according to fiber intake, ultra-processed food (UPF) consumption, sex, body mass index, and socioeconomic status.

Methods: A cross-sectional study was conducted with 91 medical students, and 82 fecal samples were analyzed. Sociodemographic and dietary data were collected via questionnaires, UPF consumption was assessed using the NOVA classification, and trained nutritionists performed anthropometry. DNA extraction and 16S rRNA sequencing were performed for the microbial analysis. Bioinformatics and statistical tests included the Dunn and Kruskal-Wallis tests, a PCoA analysis, PERMANOVA, ANOVA, Spearman's rank correlation, and alpha and beta diversity metrics.

Results: Dietary fiber intake strongly influences gut microbiota composition. Lower fiber intake was associated with a higher prevalence of Parabacteroides and Muribaculaceae. Prevotella was more prevalent in individuals with lower UPF intake, while Phascolarctobacterium was prevalent in those with higher UPF consumption. Significant differences were associated with sex and UPF consumption but not BMI or SES. Women consumed more UPF, which correlated with distinct gut microbiota profiles.

Conclusions: This study highlights the significant impact of diet, particularly fiber intake and UPF, on gut microbiota composition, emphasizing the importance of dietary habits in maintaining gut health.

Keywords: diet; fiber intake; gut microbiota; medical student; obesity; overweight; socioeconomic status; ultra-processed food.

Figure 1

Composition of gut microbiota across different BMI and SES categories by sex. (A) Samples grouping according to sex and BMI. (B) Samples grouped according to SES and sex.

Figure 2

Distribution of alpha diversity metrics (observed ASVs, Shannon, Simpson). (A) Sex, (B) BMI, (C) SES, (D) national consumption of UPF, (E) energy contribution of UPF by tertiles.

Figure 3

Beta diversity (Atkinson distance). (A) Sex, (B) SES, (C) BMI, (D) national consumption of UPF, and (E) energy contribution of UPF by tertiles. The points on the graph represent the bacterial communities of each subject, with points closer together indicating more similar bacterial communities.

Figure 4

Distribution of genera that were significantly enriched based on UPF consumption and fiber intake (p-values ≤ 0.01). (A) Genera enriched according to the national consumption of UPF. (B) Genera enriched according to the tertiles of UPF consumption. (C) Genera enriched in participants according to the meeting of the recommendation of fiber intake. (D) Genera enriched in participants with a fiber intake according to tertiles.

Figure 5

Spearman correlations between bacterial genera and UPF consumption and fiber intake. Asterisks indicate p-values < 0.05. A positive Spearman correlation suggests that higher UPF consumption or fiber intake values are associated with a higher relative abundance of the taxa. Negative correlations indicate that higher values of UPF consumption or fiber intake are associated with a lower relative abundance of the taxa.