Are changes in faecal short-chain fatty acid profiles possible under the influence of a vegetarian diet?

Background. Differences in gut microbiota composition between vegetarians and individuals consuming mixed diets are well documented. Increased dietary fibre promotes bacterial fermentation, producing short-chain fatty acids (SCFA). This study analysed whether a shift to a lacto-ovo-vegetarian diet alters faecal SCFA profiles.
Material and methods. Seventy-five healthy adults were enrolled and divided into two groups: participants who adopted a lacto-ovo-vegetarian diet for one month, and a control group who maintained their usual diet. The study was conducted in 2023–2024 in Poznań, at the Department of Bromatology, Poznań. University of Medical Sciences.
Results. Baseline faecal SCFA concentrations did not differ significantly between groups. After 30 days, the study group (SG) showed significant changes in acetic acid concentrations compared with baseline. Propionic acid concentrations also differed significantly between the study group and the control group (CG) after four weeks. Within the SG, significant changes in propionic acid were observed between baseline, two weeks, and four weeks. No significant differences were observed in butyric acid concentrations.
Conclusions. Although some changes in acetic and propionic acid concentrations were observed, the overall lack of consistent differences in SCFA profiles may be explained by insufficient increases in dietary fibre intake. Fibre intake remained comparable between groups and did not increase in the study group. Since fibre is the primary substrate for SCFA production by intestinal bacteria, its limited consumption likely constrained broader changes in faecal SCFA concentrations.