Effect of Plant-Based Diets on Gut Microbiota: A Systematic Review of Interventional Studies

Abstract

Plant-based diets have grown increasingly popular across the globe, mainly for their health and environmental benefits. Several studies have identified a link between plant-based diets and the decreased risk of developing cardiovascular diseases, obesity, and other health issues. We systematically reviewed human interventions to identify the relationship between various plant-based food items and the gut microbiome, alongside the biochemical and anthropometric measurements as secondary findings. The study selection process was completed using the COVIDENCE platform. Overall, 203 studies were identified, of which 101 were chosen for title and abstract screening by two independent authors. Following this process, 78 studies were excluded, and the full texts and the reference lists of the remaining 23 records were reviewed using the review eligibility criteria. A manual search yielded five additional articles. In the end, 12 studies were included in the systematic review. We found evidence for short- to moderate-term beneficial effects of plant-based diets versus conventional diets (duration ≤ 13 months) on gut microbiome composition and biochemical and anthropometric measurements in healthy participants as well as obese, cardiovascular, and rheumatoid arthritis patients. However, contradictory results were observed for Enterobacteriaceae, at the family level, and for Faecalibacterium and Coprococcus, at the genus level, of gut microbiome composition. The relationship between plant-based diets and the gut microbiome, alongside their underlying metabolic and inflammatory effects, remains largely unexplored. Hence more interventional studies are needed to address these questions.

Keywords: gut microbiome; metabolome; plant-based diet.

Figure 1

PRISMA 2020 flow chart detailing the study selection process.

Figure 2

Higher abundances of bacterial taxa in vegetarian/vegan intervention diets. The figure was created and edited from the images available on Canva.com using a Pro Content License.

Figure 3

Low abundance of bacterial taxa in vegetarian/vegan intervention diets. The figure was created and edited from the images available on Canva.com using a Pro Content License.

Figure 4

The influence of vegan/vegetarian diets on gut microbiota composition and biochemical and anthropometric levels in the healthy and unhealthy (metabolic and autoimmune disturbed) subjects. Note: short-chain fatty acids (SCFAs), postprandial (post-meal) glycemic response (PPGR), systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol (TC), triglycerides (TRG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), low-density lipoprotein-cholesterol (LDL-C), body mass index (BMI). References under healthy pattern for microbiota composition-Significant increase [18]/no changes in diversity [16,23,24], no changes in alpha-diversity [16], increase [16]/no differences in richness [16,23,24]; for biochemical component- increase in SCFAs [23], increase in butyrate-production pathway and acetyl-coA and X4-aminobuthrate-succinate pathways [24], lowered PPGR [24], lowered concentration of inflammatory markers [18,22,23], improved cardiometabolic health [23], low diversity of T-cell repertoire and low expression levels of IgE [18]; for anthropometric-decrease in BMI [21], mo changes in BMI [18,24]. References under unhealthy pattern for microbiota composition-significant increase in diversity [19,21,22,25], no changes in diversity [14,20], decrease in alpha-diversity [21], increase in richness [14,21,22]; for biochemical component–decrease in acetate, butyrate & propionate [14], no increase of SCFAs [19], increase of SCFAs [21,22], no changes in plasma TMAO, acyl-carnitine, or choline [21], increase plasma 1-carnitine [21], improved cardiometabolic health [22], lowered inflammatory markers concentration [22]; for anthropometric-decrease in TC, LDL-C and BMI [17,20,21,22,25], decrease in SBP & DBP, TC, TRG, LDL, HDL [21,22]. The figure was created and edited from the images available on Canva.com using a Pro Content License.