Comparative Study on Gastrointestinal Absorption Rates: Gel-Based vs. Liquid Fueling

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Based on peer-reviewed research from international sports science journals, this article provides an in-depth analysis of how “supplement form” affects athletic performance, combined with Taiwan-specific riding and race scenarios, offering actionable training nutrition advice.

Energy gels, energy chews, sports drinks, energy bars—each form of supplementation has its own strengths and weaknesses in absorption rate and gastrointestinal tolerance, which in turn influences supplement strategy choices.

In Taiwan’s endurance sports community—whether it’s hill-climbing enthusiasts tackling the Wuling ascent from the west, long-distance riders heading east through the Huadong Rift Valley, or participants in the Sun Moon Lake loop, Taroko Marathon, or 226 km Ironman triathlons—the topic of “supplement form” 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 nutrition—this “free margin for improvement.” In fact, when training volume and equipment are comparable, the quality of nutritional strategy is often the decisive variable separating finishers from DNFs, and personal bests from blow-ups. This article will walk you through the complete context—from cellular molecular mechanisms and randomized controlled trial evidence to dose-response curves and practical application—debunking long-standing myths so that your supplement strategy is truly built on science.

Review of Academic Research

Regarding the scientific exploration of “supplement form,” leading 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 form our current understanding of this topic:

1. Pfeiffer B et al. (2010, MSSE) compared the oxidation rates and gastrointestinal tolerance of energy gels, bars, and drinks.

2. Pfeiffer B et al. (2010, IJSNEM) studied gastrointestinal responses to solid vs. semi-solid carbohydrates.

3. Guillochon M and Rowlands DS (2017, IJSNEM) compared oxidation of different carbohydrate forms.

4. Rowlands DS et al. (2012, MSSE) studied absorption of multiple transportable carbohydrates.

Looking across these studies, the scientific picture of “supplement form” is not a single fixed conclusion but rather one that is continually refined and deepened as research methods advance. Early studies predominantly 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 experimental and control, greatly reducing noise from individual differences. However, extrapolation of research findings still requires caution: the responses of well-trained subjects in the laboratory may not fully translate to general amateur athletes; 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 may determine medal placement in elite competition, but its significance is relatively limited for recreational riders.

Core Mechanisms

Liquid supplementation (sports drinks) empties from the stomach quickly and is absorbed rapidly, making it suitable for high-intensity moments requiring fast energy delivery, but overly high concentrations delay gastric emptying; energy gels require water to avoid retention due to high osmolarity; chews and semi-solids provide satiety and a more gradual release; energy bars contain fiber and fat, absorb most slowly, and are suited for low-intensity, long-duration segments.

To truly understand how “supplement form” 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 oxygen and fuel delivery, muscle cells handle energy conversion and mechanical contraction, the central nervous system regulates motor unit recruitment and perceived fatigue, while the gut and liver form the hub of nutrient absorption and metabolism. The reason these mechanisms translate into measurable performance differences is precisely because they act on one (or multiple) critical links in this chain. The table below summarizes the key points of action at different physiological levels for this topic, 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 direction of adaptation |

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

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

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

Two dimensions deserve particular emphasis: “dose-response” and “temporal dynamics.” The same nutritional intervention, at different dosages and different timing, can produce vastly different or even opposite effects—this is precisely why many popular recommendations remain one-sided. Only by understanding the mechanisms can we judge “when to use it, how much to use, and when,” 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, limitations often stem from the accumulation of phosphagen system byproducts and glycolytic metabolites; in multi-hour endurance events, limitations shift toward the combined effects of glycogen depletion, rising core temperature, fluid and electrolyte imbalance, and central fatigue. The reason “supplement form” deserves in-depth exploration is precisely because it can target certain of these limiting factors. This also reminds us that no nutritional strategy can be evaluated in isolation from the “exercise context”—a supplement rhythm suited 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 rigidly adhering to a fixed formula. This ability to “adjust according 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 discomfort, or even interfere with training adaptations. The table below outlines the dose-effect correspondence for “supplement form” and serves as the most important quantitative reference when developing a personal supplement plan:

| Dose / Condition | Effect Description |

|—|—|

| Sports drinks | Fast absorption; concentration needs to be controlled |

| Energy gels | Require water |

| Chews/Semi-solids | Sustained release + satiety |

| Energy bars | Slowest; suitable for low-intensity segments |

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 point, there is no additional benefit while 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; each individual’s body weight, metabolic rate, gut tolerance, and genetic background will cause the optimal dose to shift individually.

Differences Across Populations

The benefits of “supplementation forms” are not equal for everyone. Age, sex, training status, body composition, and genetic background all significantly modulate an individual’s 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 Athletes | Advanced athletes have more mature physiological adaptations; responses are often more stable but with smaller marginal gains | Beginners should start conservatively with low doses to build tolerance first |

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

| Young vs. Older Athletes | Older athletes often experience reduced absorption efficiency and anabolic resistance | Older athletes may require higher doses or better timing |

| Body Size Differences | Body weight directly influences the absolute amount calculated per mg/kg or g/kg | Always convert to a dose corresponding to individual body weight rather than copying general guidelines |

When interpreting “individual differences,” one must also be wary of a common statistical pitfall: studies typically report “group mean responses,” but beneath the average often lies enormous individual variability. In the same intervention, some may be responders, some non-responders, and some even negative responders. This is why even when a study shows “average effectiveness,” you still need to determine through your own experimentation which category you fall into. The recommended approach is to conduct personalized A/B testing: across two training sessions with conditions as similar as possible, adopt and then omit the strategy respectively, comparing power, heart rate, and subjective feelings. Repeat several times before drawing conclusions. This empirical spirit of “using yourself as the sample” is the essential path from group science to personal prescription.

Take the common amateur endurance population in Taiwan as an example: many are masters athletes over 35 who train around their work schedules. 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—meaning correct nutritional intervention can yield relatively greater room for improvement. Female athletes, meanwhile, need to pay particular 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 translate to the training plan and the race course. Below is a practical framework for converting “supplementation forms” into concrete training and race-day operations:

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

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

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

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

• Holistic Context: Nutrition is one component of training, sleep, recovery, and psychology; a single supplement cannot compensate for sleep deprivation or flawed training design.

Using a one-week training schedule as an example, it is recommended to rehearse different supplementation scenarios during key midweek high-intensity sessions (such as threshold intervals or repeated climbs) and weekend long-distance rides: 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, reserving mental resources for pacing and tactical decisions. Remember, the goal of a nutritional strategy is not to pursue theoretical perfection, but to remain stable and reliable under the fatigue, heat, and pressure of a real race.

When executing a nutrition plan, the most common mistake many people make is “being serious only on race day while eating casually during regular training.” This is precisely putting the cart before the horse: regular training is the ideal laboratory for building gut tolerance, testing dosages, and cultivating fueling rhythm. If you hope to execute 80 grams of carbohydrate per hour on race day, you must rehearse it repeatedly in training until your body becomes accustomed; if you plan to rely on a certain 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. Additionally, do not 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 seriously as part of training, rather than a last-minute accessory before race day, and your improvement curve will be noticeably different.

Local Application in Taiwan

Taiwan’s unique climate, terrain, and race culture add local considerations to the application of “supplementation forms.” 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 contexts of temperate countries. This means hydration and fueling recommendations from foreign literature often need to be “adjusted upward.” In events like the Westbound Wuling climb, which ascends from sea level to 3,275 meters, the appetite suppression of high altitude, low temperatures, and prolonged exercise pose a severe test for energy planning.

Regarding local fueling options, Taiwan’s abundant bananas, sweet potatoes, pineapples, sports drinks, and convenience store ready-to-eat foods can all be incorporated into fueling strategies; the extremely high density of convenience stores also makes mid-ride refueling on long-distance rides relatively easy. It is recommended that Taiwanese cyclists planning classic routes such as Sun Moon Lake, Wuling, Beiyi, Buyan Ting, or the Eastbound climb survey fueling points along the way in advance, and strengthen sodium and fluid intake given Taiwan’s hot, humid environment. Athletes in the Taroko Marathon, Taipei Marathon, and various triathlon events across the island should likewise incorporate these local climatic factors into their individualized nutrition plans to perform at their best under subtropical conditions.

Common Myth-Busting

Myth: The myth is that “energy gels are always absorbed faster than food.” In reality, highly concentrated gels without adequate water may delay absorption due to high osmolarity; the supplementation form should be matched to intensity and timing.

These myths spread widely often because they “sound reasonable,” are easily passed 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 under the scrutiny of randomized controlled trials. The field of sports nutrition is especially rife with oversimplified “panacea” marketing that compresses complex dosages, timing, and individual differences into a single slogan. The next time you hear a categorical nutritional claim, it is worth asking: “What is the level of evidence for this claim? Who is the target population? Are the dosage 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

“Supplementation forms” is a topic in sports nutrition with 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 panacea—the key lies in correct dosage, 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 transform general guidelines into a personalized prescription that suits you. May every rider sweating on Wuling, in the Rift Valley, or on round-island routes 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, remember—your fuel bottle holds not just water and sugar, but an entire validated system of sports science.

Related Reading

• Gastrointestinal Tolerance of Energy-Dense Foods in Ultramarathon Racing: A Fueling Study for Trail Events
• Solid Food vs. Energy Gels During Competition: How to Choose the Fueling Form That Suits You Best
• A Complete Comparison of Road Running Fuel Products: Gastrointestinal Tolerance Analysis of Gels, Bars, and Liquid Fuel
• Electrolyte Supplementation Strategies for Summer Cycling in Taiwan: A Quantitative Study of Sodium, Potassium, and Magnesium Supplementation for High Sweat Rates