Summary:
Athletic performance is influenced by the ability to adequately consume, digest, and absorb nutrients. As a result, research on gastrointestinal function in athletes has traditionally focused on nutrient absorption and the management of gastrointestinal symptoms. More recently, attention has shifted towards the gut microbiome, the community of microorganisms living in the gastrointestinal tract, which may influence athlete health and performance. Evidence suggests that athletes have a distinct gut microbiome compared with the general population. Studies have reported greater microbial diversity and higher concentrations of short-chain fatty acids in athletes, along with an increased abundance of certain bacterial groups, while lower levels of others have been observed. These differences are thought to be partly related to dietary intake. Some studies also suggest functional implications, with greater abundance of lactate-metabolising bacteria associated with improved endurance performance and relationships observed between training volume and specific bacterial populations. This observational study investigated differences in gut health during periods of high and low training load in elite rowing athletes. Twenty-three highly trained rowers provided 24-hour stool samples during both training phases. Microbiome composition and short-chain fatty acid concentrations were analysed from the samples. Dietary intake and diet quality were assessed using three-day weighed food records to determine macronutrient and fibre intake. Gastrointestinal patterns differed between training loads. Stool frequency was higher during the high training phase, and a larger proportion of athletes were unable to produce a stool sample during the low training phase. Concentrations of short-chain fatty acids were also greater during the high training phase. Microbial diversity was slightly lower during the high training phase. Additionally, the abundance of certain bacteria increased during high training, while the ratio of others decreased. Overall, this observational study found that training load was associated with changes in several indicators of gut health, including microbiome composition, short-chain fatty acid production, stool frequency, and diet quality. However, the implications of these changes for athlete health and performance remain unclear. Further research is required to clarify the mechanisms underlying these relationships and to determine whether modifying gut health could improve athletic outcomes.
Abstract:
Background: Despite the importance of the gut microbiome on physical performance and health, little is known on the impact of training on an athlete’s gut health. Objective: This study investigates the effect of training load on markers of gut health. Methods: Whole stool (24 h) samples were collected from 23 highly trained rowers (mean ± SD; age 19.2 ± 1.1 y; weight 80.1 ± 11.4 kg; height 1.83 ± 0.09 m) following periods of high (HT) and low training load (LT). The microbiome and short-chain fatty acid concentrations were characterized from the whole stool samples. Three-day weighted food records were used to determine diet quality (ADIcore), macronutrient, and fiber intakes during HT and LT. Results: By design, training duration (147%) and intensity (130%) were greater during HT, compared with LT (p < 0.001). Carbohydrate, fat, protein, and fiber intake remained stable, but ADIcore was higher in HT (55 ± 10) compared with LT (49 ± 9; t(15) = 2.78, p = 0.014; CI: 1.34 to 10.155). Stool frequency (1.11 ± 0.47 vs 0.67 ± 0.76; p = 0.007) was greater in HT compared with LT, and a greater number of participants were unable to produce a stool sample during LT (8% vs 47%). Short chain fatty acid (SCFA), propionic (120.64 ± 30.06 mm vs 91.35 ± 34.91 mm; p = 0.007), and butyric acid (104.76 ± 50.02 vs 64.23 ± 22.05 mm, p = 0.003) concentrations were greater in HT compared with LT. Alpha diversity, Shannon–Wiener diversity index (3.43 ± 0.37 vs 3.67 ± 0.34, p = 0.09) was lower in HT than LT. The abundance of the dominant Bacteroidia was greater at HT compared to LT and ratio of Firmicutes to Bacteroidota (n = 16, 1.31 ± 1.19 vs 4.29 ± 3.88, t(15) = -3.44, p = 0.04, CI = -4.82 to −1.13) was lower in HT compared to LT. Conclusion: Results of this study indicate that gut microbiome, SCFA concentrations, stool frequency, and diet quality vary between periods of high and low training load in athletes. The relationship between these factors and impact of such changes in gut health is currently unclear and warrants further investigation.
Article Publication Date: 21/05/2025
DOI: 10.1080/15502783.2025.2507952
