Summary: Short-term, high-protein dietary periods were linked with instability in the gut microbiome, which appears to correspond with reduced endurance performance in elite athletes.
Source: Anglia Ruskin University
New research indicates that instability in the gut microbiome may undermine performance in highly trained endurance athletes, and that short-term high-protein diets are associated with such instability.
A UK-based team of researchers studied a group of well-matched, highly trained endurance runners to assess how short-term high-protein and high-carbohydrate dietary strategies affected measured performance and gut microbial communities. The randomized, double-blind repeated-measures trial examined changes in bacterial, viral, and bacteriophage populations alongside time-trial outcomes.
The trial found that athletes following a high-protein diet experienced marked changes in their gut microbiome, including reduced diversity and altered composition of the gut phageome, and increases in specific viral and bacterial groups. These microbiome disturbances were associated with a substantial decline in performance: time-trial results fell by 23.3% for the high-protein intervention.
By contrast, a short-term high-carbohydrate dietary period was linked with improved performance, showing a 6.5% average improvement in time-trial completion. This high-carbohydrate phase was associated with increased abundance of Ruminococcus and Collinsella bacterial species, which coincided with better endurance outcomes for the cohort overall.
Importantly, participants who maintained a more stable gut microbial community across dietary changes consistently performed better than those whose microbiomes shifted more dramatically. The authors highlight that gut microbial stability during dietary periodization correlated with greater athletic performance in this highly trained, well-matched group of runners.
Lead co-author Dr Justin Roberts, Associate Professor in Health and Exercise Nutrition at Anglia Ruskin University, emphasized the link between microbial stability and performance. He cautioned that while the study cannot definitively prove the high-protein diet alone caused the performance drop, the observed shifts in gut communities following a short-term high-protein period appeared associated with poorer outcomes.
The research team suggests several plausible mechanisms behind this association. Changes to the gut microbiome could affect intestinal permeability, nutrient absorption, and the signaling pathways between the gut and the brain—the gut-brain axis—which may alter perceived effort, gastrointestinal comfort, or other factors that influence endurance performance. Acute gut imbalance can also produce symptoms such as cramps or nausea, which directly impair exercise capacity.
Diets in the study were tightly controlled and balanced, reducing the likelihood that macronutrient intake alone explains the performance differences. Instead, the evidence points to the microbiome response to dietary periodization as a potential mediator between dietary strategy and athletic outcomes. The authors advise athletes and support staff to consider the potential effects of short-term dietary manipulations on gut flora when planning training and competition nutrition.
About this microbiome and diet research news
Author: Jamie Forsyth
Source: Anglia Ruskin University
Contact: Jamie Forsyth – Anglia Ruskin University
Image: The image is in the public domain
Original Research: Open access. “Gut Microbial Stability is Associated with Greater Endurance Performance in Athletes Undertaking Dietary Periodization” by Justin Roberts et al. mSystems
Abstract
Gut Microbial Stability is Associated with Greater Endurance Performance in Athletes Undertaking Dietary Periodization
Dietary manipulation—alternating short-term periods of high-protein or high-carbohydrate intake—is commonly used in elite athletic training with the aim of optimizing performance. Such interventions are likely to affect the composition and stability of the gut microbiome. This study investigated how acute high-protein or high-carbohydrate diets influence endurance performance and associated shifts in bacterial, viral (free viral particles), and inducible bacteriophage communities.
In a double-blind, repeated-measures randomized controlled design involving well-matched, highly trained endurance runners, the high-carbohydrate intervention improved time-trial performance by an average of 6.5% (P < 0.03) and was associated with expansion of Ruminococcus and Collinsella species. Conversely, the high-protein intervention reduced performance by an average of 23.3% (P = 0.001) and led to significantly lower diversity and altered composition of the gut phageome (IV diversity P = 0.04; composition changes in IV and FVP P = 0.02), along with enrichment of Sk1virus and Leuconostoc populations.
Across dietary conditions, the athletes who showed the smallest shifts in microbial community composition during periodization demonstrated the greatest endurance performance. The findings suggest that gut microbial stability during acute dietary manipulation is associated with better athletic performance in this cohort. Coaches and athletes should consider the potential impact of dietary periodization on gut flora and plan nutrition strategies accordingly.