An Interventional Soylent Diet Increases theBacteroidetestoFirmicutesRatio in Human Gut Microbiome Communities: 141 : Official journal of the American College of Gastroenterology | ACG

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Abstracts: ACCEPTED: COLON

An Interventional Soylent Diet Increases theBacteroidetestoFirmicutesRatio in Human Gut Microbiome Communities

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Hsu, Ryan BS1; McCormick, Dylan BA2; Seitz, Mitchell Lee J. Jr. BA3; Arkin, Adam PhD2

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American Journal of Gastroenterology 112():p S67-S69, October 2017.
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Introduction: Our knowledge of the relationship between the gut microbiome and health has rapidly expanded in recent years. In particular, diet has been shown to affect health outcomes such as obesity and intestinal inflammation by altering microbiome composition. Among consumers seeking healthy alternatives to traditional diets, liquid-meal replacements such as Soylent 2.0 have become increasingly popular. However, the effects of these substitutes on the gut microbiome remain largely uncharacterized. This study aims to characterize the changes in gut microbiota composition resulting from a short-term Soylent 2.0 diet.

Methods: Fourteen participants were selected and separated into either the control group (n=5) or Soylent group (n=9). Participants in the control group adhered to their regular reported diets for the duration of the study, while those in the Soylent group underwent an interventional Soylent-only diet between regular diet phases (Figure 1). Subjects completed electronic daily logs reporting diet and any discomfort. Eight fecal samples per participant were collected using fecal sampling kits, which were sent for V4 16S rDNA sequencing. Reads were clustered into operational taxonomic units (OTUs) and identified against the GreenGenes 16S database.

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Figure:
The study consists of three distinct phases. During Phase A, all participants adhere to their reported regular diets in order to establish their baseline microbiome composition. In Phase B, the Soylent group switches to an all-Soylent diet, while the regular group maintains a regular diet. In Phase C, all groups adhere to a regular diet. This study design allows us to observe microbiome community composition before, during, and after a Soylent dietary intervention. Fecal samples are collected for 16S sequencing on the eight indicated days.

Results: We find that an individual's within-sample diversity (α-diversity) is not significantly altered by an all-Soylent diet. In addition, principal coordinate analysis using the unweighted UniFrac distance metric (β-diversity) shows that samples cluster strongly by individual and not by dietary phase (Figure 2). Furthermore, we find that a Soylent diet significantly increases the medically-relevant Bacteroidetes to Firmicutes ratio (Figure 2).

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Figure:
(A) Principle coordinate analysis with unweighted UniFrac (which scores microbiome similarity based on phylogenetic similarity) shows samples cluster strongly by participant. Samples that were collected on Soylent diet days (denoted by x's) do not cluster together, suggesting that a short-term Soylent diet does not significantly affect which species are found in an individual's microbiome or cause a convergence in microbiome composition across individuals. B) Changes in the relative abundance of four major phyla in each diet-phase arm. The ratio of Bacteroidetes to Firmicutes abundance changes significantly between the diet groups during a Soylent dietary intervention (P=0.028 for phase B). No significant change is found between the groups during regular diet phases (P=0.852 for phase A and P=0.987 for phase C). All P-values were calculated using two-tailed t-tests.

Conclusion: Our results show that a short-term Soylent diet does not significantly affect microbiome diversity or the presence of specific species. Additionally, we report a significant transient increase in the Bacteroidetes to Firmicutes ratio in participants undergoing a Soylent diet, which has been associated with a lower risk of obesity and reduced intestinal inflammation. Future studies could employ transcriptomics and metabolomics to characterize changes in gene expression and metabolite profiles resulting from a Soylent diet. As additional research demonstrates the interplay of specific microbial consortia in influencing certain health outcomes, producers and consumers should consider the gut microbiome as an essential component of human health.

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Figure:
The nutritional facts for the Soylent 2.0 drink.
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