Multiple Transportable Carbohydrates During Exercise

Abstract

The concept of multiple transportable carbohydrates (MTC) refers to a combination of saccharides that rely on distinct transporters for intestinal absorption. Ingestion of MTC during prolonged exercise has been purported to increase carbohydrate absorption efficiency, increase exogenous carbohydrate oxidation, reduce gastrointestinal (GI) distress, and improve athletic performance when carbohydrate intake is high (>50-60 g·h⁻¹). Although reviews of MTC research have been published previously, a comprehensive literature evaluation underscoring methodological limitations has not been conducted to guide future work. Accordingly, this review outlined the plausible mechanisms of MTC and subsequently evaluated MTC research based on several factors, including participant characteristics, exercise modality, exercise task, treatment formulation, treatment blinding, and pre-exercise nutrition status. A total of 27 articles examining MTC during exercise were identified and reviewed. Overall, ingestion of MTC led to increased exogenous carbohydrate oxidation, reduced GI distress, and improved performance during cycling lasting ≥2.5 hours, particularly when carbohydrate was ingested at ≥1.2 g·min⁻¹. Despite the apparent benefits, several limitations in the literature were apparent, including that only 3 studies used running, only 2 studies were conducted in the field, most participants were fasted, and women and adolescents were underrepresented. In addition, the majority of the studies fed carbohydrate at ≥1.2 g·min⁻¹, which may have inflated levels of GI distress and exaggerated performance decrements with single-saccharide feedings. Based on these limitations, future MTC investigations should consider focusing on running, examining team-based sports, including women and adolescents, conducting experiments under field conditions, examining the modifying effects of pre-exercise nutrition, and using modest feeding protocols (1.0-1.2 g·min⁻¹).

Influence of a caffeine mouth rinse on sprint cycling following glycogen depletion

“…That exercise performance is attenuated with low carbohydrate (CHO) availability, yet certain training adaptations are enhanced with low endogenous CHO, presents a challenge to athletes aiming to maximize training quality (Impey et al, 2015). Exogenous supply of CHO has the potential to improve exercise performance (Stellingwerff & Cox, 2014;Wilson, 2015), particularly high-intensity exercise that is more reliant on CHO than fat oxidation (Spriet, 2014). Moreover, numerous studies have described attenuated performance during high-intensity exercise when endogenous CHO availability is limited (Gavin, Myers, & Willems, 2015a, 2015b.…”

A Hydrogel Drink With High Fructose Content Generates Higher Exogenous Carbohydrate Oxidation and a Reduced Drop in Dental Biofilm pH Compared to Two Other, Commercially Available, Carbohydrate Sports Drinks

“…Hypertonic drinks have also been suggested to cause water retention in the intestine and carbohydrate malabsorption which might increase the risk of gastrointestinal (GI) discomfort (6). While numerous studies have investigated substrate utilization and GI responses following ingestion of highly concentrated (>13%) carbohydrate drinks during exercise [as reviewed by Wilson (7)], these drinks were not commercially available and often ingested at rates wellabove what is generally recommended during prolonged exercise (up to 90 g carbohydrates•h −1 ), thereby limiting applicability of the results.…”

Sport Supplements and the Athlete’s Gut: A Review

“…One strategy to reduce GI symptoms associated exogenous carbohydrate ingestion is using mixed glucose-fructose products/foods 70 . Glucose and fructose rely on separate, saturable transporters for intestinal absorption, and when carbohydrate intakes exceed 50–60 g/h, supplying carbohydrate as a glucose-fructose mixture (as opposed to a single saccharide) enhances stomach emptying and reduces malabsorption and its associated symptoms 70 . In practice, it can be a challenge to determine the glucose-to-fructose ratio of any given product or food since there is no labelling requirement in the United States to list amounts of individual saccharides, but Wilson et al 71 does provide estimates of the glucose-to-fructose ratio of 80 different foods and products used during a 70.3-mile triathlon.…”

“…One strategy to reduce GI symptoms associated exogenous carbohydrate ingestion is using mixed glucose-fructose products/foods 70 . Glucose and fructose rely on separate, saturable transporters for intestinal absorption, and when carbohydrate intakes exceed 50–60 g/h, supplying carbohydrate as a glucose-fructose mixture (as opposed to a single saccharide) enhances stomach emptying and reduces malabsorption and its associated symptoms 70 .…”