Trending Topics pieces (Article Analyses, Evidence Clips and Other Topics) are published in timely response to recent media and journal articles, position statements, clinical guidelines, etc. Since they are based on the most recent evidence/publications, they may not be consistent with PEN evidence in other PEN content areas. As soon as possible, when this occurs, the PEN content will be reviewed and updated as needed.
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Gut Microbiota in Nutrition and Health
This article, on the role of the gut microbiota in nutrition and health, is another in the BMJ series of open access, peer-reviewed articles examining controversial nutrition topics where there are uncertainties in the evidence and debate among experts.
Most of the human studies of the gut microbiota and its associations with disease conditions are case control observational studies, conducted at one point in time (1). It is not possible from these studies to know whether the patterns of microbiota caused the disease or whether the disease, its treatment or some related factor caused the microbiota pattern. Animal studies of some topics are suggestive of a causal relationship, but the mechanisms might be different in animals versus humans (1). Future longitudinal and randomized trials will help to understand these relationships.
This BMJ article describes the gut microbiota and its associations with health, the influence of diet and medication on the microbiota, and how the gut microbiota can be manipulated by diet, probiotics and dietary fibre. It summarizes the current state of understanding of this complex topic, describing what is known from human randomized trials and animal studies and current areas yet to be clarified.
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References - Valdes AM, Walter J, Segal E, Spector TD. Role of the gut microbiota in nutrition and health. BMJ. 2018 Jun 13;361:k2179. doi: 10.1136/bmj.k2179. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/29899036
Posted: 2019-04-01
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Microbiome Study
The American Gut Project is the first crowd-funded, citizen scientist cohort that examined the microbial sequence data of 
15,096 samples from >10,000 human participants from the United States, United Kingdom and Australia. The researchers set out to examine the diversity of the industrialized human microbiome, and to look for associations between health, lifestyle and dietary factors. The researchers found that participants who reported consuming ≥30 different types of plant species each week had greater microbial diversity than those who reported consuming only ≤10 types of plant species weekly. Self-categorization of diet as “vegan” or “omnivore” had less of an impact on microbial diversity than quantification of the numbers of plant species consumed. The hypothesized implications of having greater microbial diversity is that more microbial species may be available to act as the fermenters of short-chain fatty acids. Therefore, a diet containing a variety of dietary fibres and resistant starches is likely to contribute to a more diverse microbial community. In addition, the participants who reported eating >30 types of plants per week had a significantly lower abundance of bacteria that carry antibiotic-resistant genes. This observational study cannot conclude causality but provides some food for thought related to dietary practices and future research focused on microbial diversity and health.
See Additional Content: Gastrointestinal System – Microbiota Background
Posted: 2018-05-18