For many years, far more attention has been paid to the microbes in our faeces than the microbes in our food, according to the authors of the new research. Indeed, very little is known about the effects of ingested microbial communities that are present in typical Western diets, “and even the basic questions of which microbes, how many of them, and how much they vary from diet to diet and meal to meal, have not been answered,” said the US-based team, writing in PeerJ.
Led by Jenna Lang from the University of California, Davis, the team behind the research characterised the microbiota of three different dietary patterns – finding that there was no significant difference in diversity among different dietary patterns, but that some taxonomic groups were correlated with the nutritional content of the meals.
“The findings of this study suggest that the microbes we eat as part of normal diets vary in absolute abundance, community composition, and functional potential,” said Lang and her colleagues.
“This variation depends on the specific ingredients in the meals, whether and how the foods are prepared and processed, and other potential factors, not explored here, including the provenance of ingredients.”
“This study begs the question: do the microbes we eat as part of our normal daily diets contribute to the composition and function of our gut microbiota?” questioned the team. “There are many questions that remain to be answered.”
In addition to questioning whether the bacteria within foods we eat influence the composition or functions of our own microbiome, the team also suggest that the bacteria within our diet may also play a functional role itself.
“Much as certain gut microbes can transform and modify dietary constituents and nutrients such as polyphenolic compounds and vitamins in the gut, it is possible that food microbes similarly modify nutritive molecules,” they suggested.
The team analysed the microbial content of three different dietary patterns in order to estimate: the average total amount of daily microbes ingested via food and beverages, and their composition in three daily meal plans representing three different dietary patterns.
The three dietary patterns analysed were: (1) the Average American (AMERICAN): focused on convenience foods, (2) USDA recommended (USDA): emphasizing fruits and vegetables, lean meat, dairy, and whole grains, and (3) Vegan (VEGAN): excluding all animal products.
All meals were prepared in a home kitchen or purchased at restaurants, before blended in order to complete microbial analysis - including aerobic, anaerobic, yeast and mold plate counts as well as 16S rRNA PCR survey analysis.
“Based on plate counts, the USDA meal plan had the highest total amount of microbes at 1.3 × 109 CFU [colony forming units] per day, followed by the VEGAN meal plan and the AMERICAN meal plan at 6 × 106 and 1.4 × 106 CFU per day respectively,” revealed the team – adding that there was no significant difference in diversity among the three dietary patterns.
“Predictive metagenome analysis using PICRUSt indicated differences in some functional KEGG categories across the three dietary patterns and for meals clustered based on whether they were raw or cooked,” said the team.
Published online, open access, doi: 10.7717/peerj.659
“The microbes we eat: abundance and taxonomy of microbes consumed in a day’s worth of meals for three diet types”
Authors: Jenna M. Lang, Jonathan A. Eisen, Angela M. Zivkovic