Effects of carbohydrate type and concentration and solution osmolality on water absorption

Shi, Xiaocai; Summers, Robert W.; Schedl, Harold P.; Flanagan, Shawn W.; Chang, Ray-Tai; Gisolfi, C. V.

doi:10.1249/00005768-199512000-00005

Cited by 114 publications

(134 citation statements)

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“…The highest exogenous-glucose oxidation efficiency occurring in the medium-fructose condition is perhaps one of the more important findings of the present study: it agrees with previous findings for enhanced glucose absorption (37) and oxidation when coingested with fructose (1), but also suggests that under the current solution characteristics (tonicity and concentration, carbohydrate type and form, ingestion rate) an ingested fructose:maltodextrin molar ratio of around 0.8 may lead to the most efficient exogenous-carbohydrate delivery and oxidation. To confirm this suggestion, other ingestion rates with the same molar ratio would need to be trialed, although it is unlikely that the relationship would hold at glucose-ingestion rates above ϳ1.0 g/min because of SLGT1 transport limitations.…”

Section: Discussionsupporting

confidence: 93%

“…While the present paper was in review, Currell and Jeukendrup (11) confirmed that a composite of fructose and glucose ingested at 1.2 and 0.6 g/min, respectively, resulted in substantially enhanced cycling time-trial performance compared with a beverage containing isoenergetic glucose only. The synergism associated with the combined hexoses was reported earlier in intestinal absorption studies by Shi et al (37), but the increased oxidation of the two hexoses is less marked (21%) at glucose-ingestion rates below saturation (1). Faster absorption and higher total exogenouscarbohydrate oxidation rates with the ingestion of composite carbohydrate solutions could result from the utilization of several different brush-border membrane hexose transport processes, namely SGLT1 for glucose, sodium-independent facilitated passive transport via GLUT5 for fructose (13,42), and possibly facilitated diffusion via GLUT2, which has a higher affinity for glucose but capacity for fructose and galactose also (42).…”

supporting

confidence: 68%

“…At the level of the duodenujejunum, carbohydrate absorption was found to be greater with beverages containing two or three transportable substrates (glucose and fructose or sucrose) than with isoenergetic beverages containing a single transportable carbohydrate (glucose or maltodextrins), suggesting that adding a second transportable substrate to a glucose solution stimulates additional transport mechanisms (36,37). Enhanced monosaccharide transport will increase water absorption by osmosis, which may increase permeability via the opening of tight junctions, leading to additional free hexose transport through the paracellular pathway (36,37).…”

Section: Discussionmentioning

confidence: 99%

“…Enhanced monosaccharide transport will increase water absorption by osmosis, which may increase permeability via the opening of tight junctions, leading to additional free hexose transport through the paracellular pathway (36,37). It is difficult to explain the reduced oxidation of exogenous glucose in the High-Fructose condition on the basis of a brush-border membrane transport mechanism, except for the possibility that increasing fructose ingestion from 0.5 to 0.7 g/min increased the competition for a shared transport mechanism with glucose (e.g., GLUT2 and paracellular pathway).…”

Section: Discussionmentioning

confidence: 99%

“…Faster absorption and higher total exogenouscarbohydrate oxidation rates with the ingestion of composite carbohydrate solutions could result from the utilization of several different brush-border membrane hexose transport processes, namely SGLT1 for glucose, sodium-independent facilitated passive transport via GLUT5 for fructose (13,42), and possibly facilitated diffusion via GLUT2, which has a higher affinity for glucose but capacity for fructose and galactose also (42). That is, because glucose and fructose are not competing for the same transporter, more total carbohydrate can be transported into the bloodstream for oxidation, increasing ox-idation efficiency in comparison to an isoenergetic amount of glucose or fructose alone (22,37). The coingestion of up to 1.2 g/min of glucose and 1.2 g/min of fructose resulted in an impressive peak combined exogenous-carbohydrate oxidation rate of 1.75 g/min (20).…”

mentioning

confidence: 99%

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Effect of graded fructose coingestion with maltodextrin on exogenous ¹⁴C-fructose and ¹³C-glucose oxidation efficiency and high-intensity cycling performance

Rowlands¹,

Thorburn²,

Thorp³

et al. 2008

Journal of Applied Physiology

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Rowlands DS, Thorburn MS, Thorp RM, Broadbent S, Shi X. Effect of graded fructose coingestion with maltodextrin on exogenous 14 C-fructose and 13 C-glucose oxidation efficiency and high-intensity cycling performance. J Appl Physiol 104: 1709-1719, 2008. First published March 27, 2008 doi:10.1152/japplphysiol.00878.2007.-The ingestion of solutions containing carbohydrates with different intestinal transport mechanisms (e.g., fructose and glucose) produce greater carbohydrate and water absorption compared with singlecarbohydrate solutions. However, the fructose-ingestion rate that results in the most efficient use of exogenous carbohydrate when glucose is ingested below absorption-oxidation saturation rates is unknown. Ten cyclists rode 2 h at 50% of peak power then performed 10 maximal sprints while ingesting solutions containing 13 C-maltodextrin at 0.6 g/min combined with 14 C-fructose at 0.0 (No-Fructose), 0.3 (Low-Fructose), 0.5 (Medium-Fructose), or 0.7 (High-Fructose) g/min, giving fructose:maltodextrin ratios of 0.5, 0. 8, and 1.2. Mean (percent coefficient of variation) exogenous-fructose oxidation rates during the 2-h rides were 0.18 (19), 0.27 (27), 0.36 (27) g/min in Low-Fructose, Medium-Fructose, and High-Fructose, respectively, with oxidation efficiencies (ϭoxidation/ingestion rate) of 62-52%. Exogenous-glucose oxidation was highest in Medium-Fructose at 0.57 (28) g/min (98% efficiency) compared with 0.54 (28), 0.48 (29), and 0.49 (19) in Low-Fructose, High-Fructose, No-Fructose, respectively; relative to No-Fructose, only the substantial 16% increase (95% confidence limits Ϯ16%) in Medium-Fructose was clear. Total exogenous-carbohydrate oxidation was highest in Medium-Fructose at 0.84 (26) g/min. Although the effect of fructose quantity on overall sprint power was unclear, the metabolic responses were associated with lower perceptions of muscle tiredness and physical exertion, and attenuated fatigue (power slope) in the Medium-Fructose and HighFructose conditions. With the present solutions, low-medium fructose-ingestion rates produced the most efficient use of exogenous carbohydrate, but fatigue and the perception of exercise stress and nausea are reduced with moderate-high fructose doses. dose response; dual-tracer method; substrate metabolism; gastrointestinal distress; fatigue IT IS NOW WIDELY ACCEPTED that ingestion of carbohydrate solutions can delay fatigue and improve endurance performance during high-intensity exercise of ϳ60 min or longer (reviewed in Ref. 25). The proposed mechanisms for performance enhancement are related to the prevention of hypoglycemia and the maintenance of high carbohydrate-oxidation rates during the later stages of exercise, when endogenous muscle and liver carbohydrate stores may become depleted (8). For these reasons and for reasons relating to hydration, there is interest from industry, scientists, and athletes in finding the formulation that will best optimize performance.During exercise, ingested glucose is rapidly absorbed into the circulation and oxidized b...

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Section: Discussionsupporting

confidence: 93%