Association Between Gut Microbiota Composition and Endurance Performance: A Study on Short-Chain Fatty Acid Energy Supply

This article is based on peer-reviewed research from international sports science journals, providing an in-depth analysis of the impact of the “gut microbiota” on athletic performance, and combining it with Taiwan’s local cycling and race scenarios to offer actionable training and nutrition advice.

The gut microbiota has been called the “forgotten organ.” Recent research has found that specific bacterial strains are closely linked to endurance performance, lactate metabolism, and energy supply, opening up a new field of exercise microbiology.

In Taiwan’s endurance sports community—whether it’s climbing enthusiasts tackling the West Route to Wuling, long-distance riders heading East through the Huatung Valley, or participants in the Sun Moon Lake loop, Taroko Marathon, or 226km Ironman triathlons—the topic of the “gut microbiota” matters because it directly determines whether you can maintain your pace in the latter stages of a race, avoid cramping and hitting the wall, and recover effectively between consecutive training days. Many amateur athletes pour all their effort into power training and equipment upgrades while overlooking this “free margin for improvement” that nutrition provides. In fact, when training volume and equipment are comparable, the quality of nutritional strategy is often the key variable separating finishers from DNFs, and personal bests from blow-ups. This article will guide you through the complete context—from cellular and molecular mechanisms, to randomized controlled trial evidence, to dose-response curves and practical application—debunking long-circulated myths and putting your fueling strategy on a truly scientific footing.

Academic Research Review

Regarding the scientific exploration of the “gut microbiota,” top international journals have accumulated rich and rigorous evidence. Below are several representative studies selected for their value in methodological design, sample populations, and strength of conclusions, which together build our current understanding of this topic:

1. Scheiman J et al. (2019, Nature Medicine) found that marathon runners’ guts are enriched with Veillonella, which can metabolize lactate to produce propionate.

2. Clarke SF et al. (2014, Gut) showed that athletes have higher gut microbial diversity.

3. Mohr AE et al. (2020, JISSN) provided an International Society of Sports Nutrition position stand reviewing exercise and the microbiome.

4. Estaki M et al. (2016, Microbiome) linked cardiorespiratory fitness with microbial diversity.

Looking at these studies as a whole, the scientific picture of the “gut microbiota” is not a single fixed conclusion, but rather something constantly refined and deepened as research methods advance. Early studies mostly used laboratory-controlled time trials or exhaustion tests; subsequent research gradually incorporated stable isotope tracing, muscle biopsies, functional magnetic resonance imaging (fMRI), and molecular biomarkers, allowing us to move from “observing phenomena” to “explaining mechanisms.” Notably, most high-quality studies employ a randomized crossover design, where each subject serves as both the experimental and control group, greatly reducing noise from individual differences. However, extrapolating research conclusions still requires caution: the responses of well-trained subjects in the laboratory may not fully translate to the average amateur athlete; and the effects of a single acute intervention may not equal long-term chronic adaptation. When reading the “effect sizes” and “statistical significance” of these studies, we must also distinguish between “statistically significant” and “practically meaningful”—a 1% improvement might decide medal placement in elite competition, but its significance is relatively limited for a recreational rider.

Core Mechanisms

Gut bacteria ferment dietary fiber to produce short-chain fatty acids (SCFAs: butyrate, propionate, acetate), which can serve as energy substrates, regulate inflammation, and maintain the intestinal barrier. Species such as Veillonella can convert lactate produced during exercise into propionate for energy, creating a “lactate recycling” cycle. Microbial diversity is also associated with anti-inflammatory effects and recovery.

To truly understand how the “gut microbiota” affects athletic performance, we must return to physiology at the cellular and systemic levels. Athletic performance is the result of multi-system coordination: the cardiovascular system handles the delivery of oxygen and fuel, muscle cells handle energy conversion and mechanical contraction, the central nervous system regulates motor unit recruitment and perceived fatigue, and the gut and liver form the hub of nutrient absorption and metabolism. The reason these mechanisms can translate into measurable performance differences is precisely because they act on one (or more) critical links in this chain. The table below summarizes the key effects of this topic at different physiological levels, helping you build a complete mechanistic picture:

| Level of Action | Key Mechanisms | Significance for Athletic Performance |

|—|—|—|

| Cellular/Molecular | Affects mitochondrial efficiency, enzyme activity, and signal transduction | Determines the efficiency of energy conversion and the direction of adaptation |

| Muscle Tissue | Regulates substrate utilization, buffering capacity, and contractile function | Affects sustainable power output and the onset of fatigue |

| Systemic Integration | Alters blood flow distribution, thermoregulation, and hormonal environment | Determines stability and safety during prolonged exercise |

| Central Nervous System | Regulates perceived fatigue, drive, and motor unit recruitment | Affects “how tired it feels” and the ability to push through |

Two dimensions deserve special emphasis: “dose-response” and “temporal dynamics.” The same nutritional intervention, at different doses and different timing, can produce vastly different or even opposite effects—this is precisely why much of the advice circulating in the community remains one-sided. Only by understanding the mechanisms can we judge “when to use it, how much to use, and when to take it,” rather than blindly following trends.

Going further, the limiting factors of athletic performance shift dynamically with exercise intensity and duration: in short, high-intensity efforts, the limits often come from the accumulation of phosphagen system depletion and glycolytic byproducts; in multi-hour endurance events, the limits shift toward the combined effects of glycogen depletion, rising core temperature, fluid and electrolyte imbalance, and central fatigue. The reason the “gut microbiota” deserves in-depth discussion is precisely because it can specifically influence some of these limiting factors. This also reminds us that no nutritional strategy can be evaluated in isolation from the “exercise context”—a fueling rhythm suitable for a 40-minute criterium may not apply to a 6-hour climbing epic, and vice versa. The more thoroughly you understand the mechanisms, the more flexibly you can adjust across different race formats, rather than clinging to a single fixed formula. This ability to “adapt to context” is precisely the dividing line between amateur athletes and those who truly understand sports science.

Dose-Response Relationship

In sports nutrition, “the dose determines both the toxicity and the benefit.” Too low a dose fails to reach the physiological threshold and is futile; too high a dose may trigger side effects, gastrointestinal distress, and even interfere with training adaptations. The table below outlines the dose-response relationship for the “gut microbiota” and serves as the most important quantitative reference when building your personal fueling plan:

| Dose / Condition | Effect Description |

|—|—|

| Dietary fiber | Substrate for SCFAs |

| Veillonella | Metabolizes lactate to produce propionate |

| High microbial diversity | Better recovery and immune function |

| Prebiotics / fermented foods | Can modulate the microbiota |

As the table shows, benefits often follow an “inverted U” or “threshold-plateau” curve: effects increase with dose until the effective threshold is reached, but beyond a certain plateau, there are not only no additional benefits, but the marginal costs (side effects, gastrointestinal burden, financial expense) rise sharply. This means “finding your own optimal dose” matters far more than “eating as much as possible.” It is recommended to progressively test different doses during training (not on race day), recording subjective feelings, gastrointestinal responses, and power data to build your own dose profile. Remember: the laboratory average is a starting point, not the endpoint; everyone’s body weight, metabolic rate, gut tolerance, and genetic background will shift the optimal dose in an individualized way.

Differences Across Populations

The benefits of the “gut microbiota” are not equal for everyone. Age, sex, training status, body size, and genetic background all significantly modulate individual response magnitude. Ignoring these differences and applying a one-size-fits-all recommendation is one of the most common mistakes in sports nutrition.

| Population Aspect | Response Characteristics | Practical Recommendations |

|—|—|—|

| Beginners vs. Advanced | Advanced athletes have more mature physiological adaptations; responses are often more stable but with smaller marginal gains | Beginners should start conservatively with low doses and build tolerance first |

| Male vs. Female | Differences in body weight, hormonal cycles, and sweat composition affect dosage and requirements | Females should individualize by body weight and pay attention to iron and energy availability |

| Young vs. Older | Older individuals often have reduced absorption efficiency and anabolic resistance | Older individuals may need higher doses or better timing |

| Body Size Differences | Body weight directly affects the absolute amount calculated per mg/kg or g/kg | Always convert to a dose relative to individual body weight; avoid copying general rules |

When interpreting “individual differences,” one must also be wary of a common statistical trap: studies mostly report “group mean responses,” but beneath the mean often lies enormous individual variability. In the same intervention, there may be strong responders, non-responders, and even negative responders. This is why even when a study shows “average effectiveness,” you still need to confirm through your own testing which category you fall into. A recommended approach is to conduct personalized A/B testing: in two training sessions with as similar conditions as possible, use and then don’t use the strategy, compare power, heart rate, and subjective feelings, and repeat several times before drawing conclusions. This empirical spirit of “using yourself as the sample” is the essential path from group science to a personal prescription.

Taking Taiwan’s common amateur endurance population as an example, many are riders over 35 who train in their spare time around work. This group simultaneously faces declining recovery speed, insufficient sleep, and time pressure, so the “return on investment” of nutritional strategies is often higher than for young elites—that is, correct nutritional interventions can yield relatively greater room for improvement. Female athletes, in particular, need to pay close attention to the effects of the menstrual cycle on metabolism and requirements, as well as whether energy availability is sufficient, to avoid falling into the low energy availability (LEA) trap while pursuing lighter body weight. After understanding population differences, you will realize: truly professional nutritional advice is always an individualized prescription that varies from person to person, not a one-size-fits-all slogan.

Practical Training Application

Theory must ultimately be implemented in training plans and on the race course. Below is a practical framework for translating the “gut microbiota” into concrete training and race operations:

• Pre-race testing principle: All nutritional strategies must be rehearsed in training first; “never try anything new on race day” is an iron rule. Gastrointestinal tolerance to new fuels takes time to build.

• Periodization mindset: Align nutritional strategies with the training cycle—the base phase can emphasize adaptation-oriented strategies, while the pre-season shifts to performance-oriented fueling optimization.

• Progressive introduction: Start with low doses and low frequency, adjust gradually based on bodily responses, and build a personalized dose and timing profile.

• Data tracking: Combine power meter data, heart rate, ratings of perceived exertion (RPE), and gastrointestinal comfort records to objectively evaluate whether an intervention is truly effective.

• Holistic context: Nutrition is one part of training, sleep, recovery, and psychology; no single supplement can compensate for sleep deprivation or poor training design.

Using a weekly training schedule as an example, it is recommended to rehearse different fueling scenarios during key midweek high-intensity sessions (such as threshold intervals or repeated climbs) and the weekend long ride: high-intensity days focus on rapid energy supply and central nervous system activation, while long-distance days focus on sustained energy delivery, gastrointestinal tolerance, and recovery. Through repeated rehearsal, your body can execute the optimal fueling rhythm “automatically” on race day, leaving mental resources for pacing and tactical decisions. Remember, the goal of a nutritional strategy is not theoretical perfection, but reliability and stability under the fatigue, heat, and pressure of a real race course.

The most common mistake people make when executing a nutrition plan is “being serious only on race day and eating carelessly during regular training.” This is precisely putting the cart before the horse: regular training is the ideal laboratory for building gut tolerance, testing doses, and cultivating fueling rhythm. If you want to execute an 80g-per-hour carbohydrate fueling plan on race day, you must rehearse it repeatedly in training until your body is accustomed to it; if you want to rely on a particular supplement, you must confirm in training that it is genuinely effective for you and free of side effects. It is recommended to integrate a nutrition log with your training log, recording the fueling content, intake timing, gastrointestinal responses, and performance data for each key session. After weeks to months of accumulation, the value of this personalized database will far exceed any generic nutrition guide. Also, don’t overlook the often-underestimated “post-training recovery fueling” component—the quality of recovery between consecutive training days often determines whether you can steadily accumulate training volume without injury, and training volume is the most fundamental engine of long-term progress. Treat nutrition as a serious part of training rather than a last-minute accessory before races, and your improvement curve will be noticeably different.

Local Application in Taiwan

Taiwan’s unique climate, terrain, and race culture add localization considerations to the application of the “gut microbiota.” Taiwan’s summer heat and humidity often push the perceived temperature above 35°C, with sweat rates and fluid/electrolyte losses far exceeding the research conditions of temperate countries, meaning that hydration and fueling recommendations from foreign literature often need to be “adjusted upward.” In events like the West Route to Wuling, which climbs from sea level to 3,275 meters, the appetite suppression of high altitude, cold temperatures, and prolonged exercise pose a severe test for energy planning.

In terms of local fueling options, Taiwan’s abundant bananas, sweet potatoes, pineapples, sports drinks, and convenience store ready-to-eat foods can all be incorporated into a fueling strategy; the extremely high density of convenience stores also makes mid-ride refueling on long distances relatively easy. It is recommended that Taiwanese riders planning classic routes such as Sun Moon Lake, Wuling, Beiyi, Buyanting, or the East Route scout fueling points along the way in advance, and strengthen sodium and fluid intake to account for Taiwan’s humid, hot environment. Athletes in the Taroko Marathon, Taipei Marathon, and various local triathlons should likewise incorporate these local climatic factors into their individualized nutrition plans to perform at their best under subtropical conditions.

Debunking Common Myths

Myth: The myth is that “probiotic supplements definitely improve performance.” In fact, the evidence remains preliminary, and the impact of dietary fiber diversity on the microbiota may be more substantial.

These myths spread widely often because they “sound reasonable,” are easy to pass along by word of mouth, or are amplified by marketing rhetoric. Yet the value of science lies precisely in testing intuition with rigorous evidence: many seemingly obvious notions fail to hold up under the scrutiny of randomized controlled trials. The field of sports nutrition is especially rife with oversimplified “magic bullet” marketing that compresses complex dosing, timing, and individual differences into a single slogan. The next time you hear a dogmatic nutritional claim, it’s worth asking: “What is the level of evidence for this claim? Who is the target population? Are the dose and timing clearly specified?” Cultivating this evidence-based critical thinking is more valuable than memorizing any single conclusion, and it is a key step for amateur athletes moving toward scientific training.

Conclusion

The “gut microbiota” is a topic in sports nutrition that combines both theoretical depth and practical value. From the academic evidence reviewed in this article, its benefits are real, but it is by no means an unconditional magic bullet—the key lies in correct dosing, appropriate timing, individualized adjustment, and synergy with overall training, recovery, and sleep. For endurance sports enthusiasts in Taiwan, while grasping the scientific principles, it is equally important to incorporate local climate, terrain, and race characteristics to translate general rules into a personalized prescription that works for you. May every rider sweating on Wuling, in the Huatung Valley, or on a round-island journey break through their limits through science-based nutritional strategies and enjoy the pure joy that sport brings. Before you next step onto the race course, don’t forget—your fuel bottle holds not just water and sugar, but an entire validated body of sports science.

Related Reading

• Gut Microbiota Effects in Endurance Sports: New Research on Lactobacillus and Athletic Performance
• Gut Microbiota and Cycling Performance: How the Microbiome Affects Your Endurance
• Exercise and the Gut Microbiota: An Emerging Performance Factor—The Second Engine from Endurance to Recovery
• Microbiome and Exercise: New Research on Gut Microbiota and Endurance Performance