The narrative review of athletic gut microbiota research, which took a team of 24 researchers approximately 18 months to compile, summarises current knowledge of the athletic gut microbiota and the factors that shape it.
The researchers concluded that the current body of literature indicates that the combination of exercise, diet and body composition promote a more ‘health-associated’ gut microbiota in athletes.
“Nearly all studies included in this review have shown positive correlations between gut taxa and exercise. Overall exercise appears to enrich microbiota diversity, stimulate the proliferation of bacteria which can modulate mucosal immunity, improve barrier functions and increase functional pathways capable of producing substances (eg butyrate and propionate) that can increase performance and health,” wrote the researchers in the International Journal of Sports Nutrition.
In the long term, they said that this research is expected to have application beyond athletes for health and wellness in larger communities.
However, they acknowledged that much work needs to be done to reach this point.
More long term studies needed
“This a Pandora’s box. A lot of the research to date has been cross-sectional, meaning data collection took place at one time point. We need more longitudinal interventions to flesh out what what is going on in the gastro-intestinal environment,” lead researcher Alex Mohr, a PhD student at Arizona State University, told NutraIngredients.
He added that another limitation with many of the studies is that they are “underpowered”, in the sense that the sample size isn’t adequate to see a “true and strong effect”.
“We would encourage investigators to carry out sample size analysis and make sure they are recruiting the right amount of subjects to detect an effect,” said Mohr, who is currently working on a paper that outlines best practice guidance for investigators.
Metagenomics and metabolomics
To date, gut microbiota research has utilised sequencing methods that rely heavily on 16S rRNA amplicon-based methodology and only assess the taxonomic composition of the gut microbiota. The problem with this is that effects on the host may be more dependent on the metabolic capacity and metabolites of the microbiota, instead of the composition. Therefore, Mohr said these methods need to be integrated with other techniques such as metagenomics and metabolomics to understand functional capacity.
“Deeper sequencing with metagenomics will give an indication of the functionality of the different microbes. Metabolomics, where we look at the metabolic outputs from the different micro-organisms, are another important part of the puzzle, because these metabolites, namely SCFAs [Short Chain Fatty Acids], can affect host health,” said Mohr.
In terms of areas for future investigation, the paper makes a number of recommendations, from exploring the gut-brain axis in athletes to investigating the impact of exercise in sedentary individuals.
Looking at why some people respond more to exercise than others is another area that the team would like to see being explored.
“Sometimes there are non-responders in exercise interventions. An important area of future research would be to look at why the gut microbiota of these individuals isn’t changing to the magnitude of others who see a much greater effect or benefit,” said Mohr.
Protein: an unknown factor
For Mohr, one area that deserves a lot of consideration is the impact of protein supplementation on the gut microbiota.
“Athletes consume more dietary supplements – in particular, protein – than any other group. How does this affect the gut microbiota? We know that in sedentary populations, high protein diets are often accompanied by a higher fat intake that seems to negatively alter the gut microbiota, producing some metabolites that are of concern. But protein powders are heavily processed, so a lot of it probably isn’t reaching the large intestine. The truth is, this is another area we just don’t know about,” he said.
To this end, the researchers recommend investigating the effect of higher protein consumption on the gut microbiota, particularly in the context of lower fat and higher fibre intakes.
Ultimately, the researchers said this body of work will define how metabolic capabilities of gut microbiota are shaped by exercise and elucidate their functional roles influencing health and disease.
Source: Journal of the International Society of Sports Nutrition
Mohr et al.
"The athletic gut microbiota"