Pectin-Alginate Does Not Further Enhance Exogenous Carbohydrate Oxidation in Running

Abstract

Purpose Maximizing carbohydrate availability is important for many endurance events. Combining pectin and sodium alginate with ingested maltodextrin–fructose (MAL + FRU + PEC + ALG) has been suggested to enhance carbohydrate delivery via hydrogel formation, but the influence on exogenous carbohydrate oxidation remains unknown. The primary aim of this study was to assess the effects of MAL + FRU + PEC + ALG on exogenous carbohydrate oxidation during exercise compared with a maltodextrin–fructose mixture (MAL + FRU). MAL + FRU has been well established to increase exogenous carbohydrate oxidation during cycling compared with glucose-based carbohydrates (MAL + GLU). However, much evidence focuses on cycling, and direct evidence in running is lacking. Therefore, a secondary aim was to compare exogenous carbohydrate oxidation rates with MAL + FRU versus MAL + GLU during running. Methods Nine trained runners completed two trials (MAL + FRU and MAL + FRU + PEC + ALG) in a double-blind, randomized crossover design. A subset (n = 7) also completed a MAL + GLU trial to address the secondary aim, and a water trial to establish background expired 13CO2 enrichment. Participants ran at 60% V˙O2peak for 120 min while ingesting either water only or carbohydrate solutions at a rate of 1.5 g carbohydrate per minute. Results At the end of 120 min of exercise, exogenous carbohydrate oxidation rates were 0.9 (SD 0.5) g·min−1 with MAL + GLU ingestion. MAL + FRU ingestion increased exogenous carbohydrate oxidation rates to 1.1 (SD 0.3) g·min−1 (P = 0.038), with no further increase with MAL + FRU + PEC + ALG ingestion (1.1 (SD 0.3) g·min−1; P = 1.0). No time–treatment interaction effects were observed for plasma glucose, lactate, insulin, or nonesterified fatty acids, or for ratings of perceived exertion or gastrointestinal symptoms (all, P > 0.05). Conclusion To maximize exogenous carbohydrate oxidation during moderate-intensity running, athletes may benefit from consuming glucose(polymer)–fructose mixtures over glucose-based carbohydrates alone, but the addition of pectin and sodium alginate offers no further benefit.

Addition of pectin-alginate to a carbohydrate beverage does not maintain gastrointestinal barrier function during exercise in hot-humid conditions better than carbohydrate ingestion alone

“…Our data do not support this proposition. Instead, they support previous observations made in thermoneutral environments during running (McCubbin et al 2019;Barber et al 2020) and cycling (Baur et al 2019;Mears et al 2020a), which reported no differences in blood glucose concentrations, substrate oxidation, or exercise performance between the two drink mixtures.…”

“…In the present study we report high rates of severe GI discomfort (GI scores over 5) in both the MAL+FRU+PEC+ALG (71%) and MAL+FRU (57%) trials relative to water (36%). We can therefore be confident that our protocol induced substantial GI distress during each experimental trial relative to previous investigations using both runners (McCubbin et al 2019;Barber et al 2020) and cyclists (Baur et al 2019;Mears et al 2020a), and increases the likelihood of detecting a difference between CHO drinks. We did note that sensations of gut discomfort were greater following MAL+FRU+PEC+ALG as compared to both the MAL+FRU and WATER.…”

“…Although previous hydrogel studies have not measured deep body temperature, we can make inferences on the likely temperature responses from similar protocols employed by others. For example, a ~1.4 °C increase in deep body temperature has been observed during a running protocol similar in duration (120-min), intensity (60% VO2max) and environmental conditions (22 °C, 50% RH; Snipe et al, 2018) to those employed by both McCubbin et al, (2019; 180-min, 60% VO2max), and Barber et al, (2020;120-min, 60% VO2max). Similarly, a ~1.4 °C increase in deep body was also observed after 90-min of cycling at 55% Wmax (Jentjens et al 2002), and would likely be reflective of the temperature responses encountered during the steady state element of the Mears et al, (2020) experiment (120 min, 55% Wmax).…”

“…It has been speculated that hydrogel formulations increase gastric emptying rates during exercise, enhance absorption of oxidizable CHO, reduce the incidence and severity of gastrointestinal symptoms, and allow provision of CHO in concentrations that far exceed what can typically be tolerated using commercially available sports drinks (Sutehall et al 2018). However, when pectin-alginate CHO drinks have been compared to traditional glucose(polymer) beverages, no differences have been shown in whole body substrate oxidation, blood glucose availability, or GI symptoms during either 90 or 180 minutes of treadmill running at 60% VO2max (McCubbin et al 2019;Barber et al 2020; both 90g . hr -1 CHO, 16% w/v), 120 minutes of cycling at 55% Wmax, (Mears et al 2020, 80g .…”

“…hr -1 , 18% w/v). In light of these findings, it is not surprising that there is no empirical evidence to support additional ergogenic benefits beyond those that are already associated with the ingestion of traditional glucose(polymer)-fructose mixtures during running (McCubbin et al 2019;Barber et al 2020) and cycling exercise (Baur et al, 2019, Mears et al, 2020. It is possible that hydrogel formulations are only ergogenic in certain contexts, such as conditions that are associated with greater GI disturbance or alterations in CHO metabolism.…”