Assessment of the Gut Microbiota during Juice Fasting with and without Inulin Supplementation: A Feasibility Study in Healthy Volunteers

Abstract

Prebiotic inulin consumption provides health benefits to the host and has also been associated with a reduction in hunger cravings. We conducted a pilot crossover study to investigate the feasibility of a juice fasting intervention with and without inulin supplementation. We also examined trends of how the microbial community in the human gut adapts to juice fasting as well as to inulin intake during juice fasting. Six healthy volunteers were fasting for three consecutive days consuming a total of 300 kcal daily provided by vegetable juices, framed by two days with a total daily calorie intake of 800 kcal, respectively. During one fasting period, participants consumed additionally 24 g of inulin daily. Stool samples were collected for the analysis of the microbial composition using 16S rRNA gene sequencing. Although no significant uniform changes were observed on the microbiome, quantitative changes in the microbial composition suggest a stronger decrease in alpha-diversity after fasting compared to the fasting intervention with additional inulin intake. The intake of inulin did not affect compliance for the fasting intervention but appeared to increase relative abundance of Bifidobacteria in participants who tolerated it well. Further studies with a larger sample size to overcome inter-individual microbiota differences are warranted to verify our observations.

Keywords: crossover study; dietary intervention; fasting; feasibility study; human gut microbiome; inulin; juice fasting; pilot study; prebiotics.

Figure 1

Study design of the crossover intervention. Two juice fasting interventions (one with additional 24 g inulin taken daily and one without inulin) separated by a six-week washout phase. Each fasting intervention consisted of five days. The first and the last day each included small light meals of 800 kcal in total. The three acute fasting days in the middle of the intervention include 300 kcal daily as vegetable juices and tea. Stool samples were collected right before and after each fasting intervention.

Figure 2

Changes in human gut microbial composition after fasting intervention and inulin intake. (A,B) Alpha diversity measures before and after fasting intervention. The lines and dots are colored according to the identities of the participants and show the individual changes in the gut microbiome community. (C) Beta diversity of bacterial samples based on Bray-Curtis distances and visualized using Non-Metric Multidimensional Scaling (NMDS). Colors correspond to participant identities and shapes to intervention phases.

Figure 3

Relative abundance of the most abundant genera at the individual level before and after fasting interventions and inulin consumption. Genera from the same family are grouped next to each other by decreasing levels of abundance and colored with a similar shade of color.

Figure 4

Bacterial composition of aggregated gut microbial samples before and after fasting interventions and inulin consumption. Relative abundance of the most abundant genera. Genera from the same family are grouped next to each other by decreasing level of abundance and colored with a similar shade. Names of the corresponding families are indicated by brackets.