Oxidation of combined ingestion of glucose and sucrose during exercise.
ABSTRACT The first purpose of the study was to examine whether combined ingestion of glucose and sucrose at an intake rate of 1.2 g/min would lead to higher oxidation rates compared with the ingestion of an isocaloric amount of glucose or sucrose alone. The second aim of the study was to investigate whether a mixture of glucose and sucrose when ingested at a high rate (2.4 g/min) would result in exogenous CHO oxidation rates higher than 1.2 to 1.3 g/min. Eight trained cyclists (maximal oxygen consumption: 64 +/- 2 mL . kg -1 . min -1 , mean +/- SE) performed 5 exercise trials in random order. Each trial consisted of 120 minutes of cycling at 50% maximum power output (63% +/- 2% maximal oxygen consumption), whereas subjects received a solution providing either 1.2 g/min of glucose (GLU), 1.2 g/min of sucrose (SUC), 0.6 g/min of glucose + 0.6 g/min of sucrose (M-GLU+SUC), 1.2 g/min of glucose + 1.2 g/min of sucrose (H-GLU+SUC), or water (WAT). Peak exogenous CHO oxidation rates in the H-GLU+SUC trial (1.20 +/- 0.07 g/min) were significantly higher ( P < .01) compared with the GLU, M-GLU+SUC, and SUC trials (0.77 +/- 0.04, 0.90 +/- 0.07, 0.98 +/- 0.04 g/min, respectively). Furthermore, peak exogenous CHO rates in M-GLU+SUC and SUC trials were significantly higher ( P < .05) compared with the GLU trial. In conclusion, combined ingestion of moderate amounts of glucose and sucrose (144 g) during cycling exercise resulted in approximately 21% higher exogenous CHO oxidation rates compared with the ingestion of an isocaloric amount of glucose. Furthermore, when a mixture of glucose and sucrose was ingested at high rates (2.4 g/min), exogenous CHO oxidation rates reached peak values of approximately 1.20 g/min.
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ABSTRACT: The consumption of carbohydrate before, during and after exercise is a central feature of the athlete's diet, particularly those competing in endurance sports. Sucrose is a carbohydrate present within the diets of athletes. Whether sucrose, by virtue of its component monosaccharide's glucose and fructose, exerts a meaningful advantage for athletes over other carbohydrate types or blends is unclear. This narrative reviews the literature on the influence of sucrose, relative to other carbohydrate types, on exercise performance or the metabolic factors that may underpin exercise performance. Inference from the research to date suggests that sucrose appears to be as effective as other highly metabolizable carbohydrates (e.g., glucose, glucose polymers) in providing an exogenous fuel source during endurance exercise, stimulating the synthesis of liver and muscle glycogen during exercise recovery and improving endurance exercise performance. Nonetheless, gaps exist in our understanding of the metabolic and performance consequences of sucrose ingestion before, during and after exercise relative to other carbohydrate types or blends, particularly when more aggressive carbohydrate intake strategies are adopted. While further research is recommended and discussed in this review, based on the currently available scientific literature it would seem that sucrose should continue to be regarded as one of a variety of options available to help athletes achieve their specific carbohydrate intake goals.International Journal of Sport Nutrition and Exercise Metabolism 04/2013; · 1.98 Impact Factor
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ABSTRACT: Almost half a century ago, researchers demonstrated that the ratio of stable carbon isotopes in exhaled breath of rats and humans could reveal the oxidation of labeled substrates in vivo, opening a new chapter in the study of fuel use, the fate of ingested substrates, and aerobic metabolism. Until recently, the combined use of respirometry and stable-isotope tracer techniques had not been broadly employed to study fuel use in other animal groups. In this review, we summarize the history of this approach in human and animal research and define best practices that maximize its utility. We also summarize several case studies that use stable-isotope measurements of breath to explore the limits of aerobic metabolism and substrate turnover among several species and various physiological states. We highlight the importance of a comparative approach in revealing the profound effects that phylogeny, ecology, and behavior can have in shaping aerobic metabolism and energetics as well as the fundamental biological principles that underlie fuel use and metabolic function across taxa. New analytical equipment and refinement of methodology make the combined use of respirometry and stable-isotope tracer techniques simpler to perform, less costly, and more field ready than ever before. © 2015 New York Academy of Sciences.Annals of the New York Academy of Sciences 03/2015; DOI:10.1111/nyas.12737 · 4.31 Impact Factor
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ABSTRACT: Fructose consumption and its implications on public health are currently under study. This work reviewed the metabolic fate of dietary fructose based on isotope tracer studies in humans. The mean oxidation rate of dietary fructose was 45.0% +/- 10.7 (mean +/- SD) in non-exercising subjects within 3--6 hours and 45.8% +/- 7.3 in exercising subjects within 2--3 hours. When fructose was ingested together with glucose, the mean oxidation rate of the mixed sugars increased to 66.0% +/- 8.2 in exercising subjects. The mean conversion rate from fructose to glucose was 41% +/- 10.5 (mean +/- SD) in 3--6 hours after ingestion. The conversion amount from fructose to glycogen remains to be further clarified. A small percentage of ingested fructose (<1%) appears to be directly converted to plasma TG. However, hyperlipidemic effects of larger amounts of fructose consumption are observed in studies using infused labeled acetate to quantify longer term de novo lipogenesis. While the mechanisms for the hyperlipidemic effect remain controversial, energy source shifting and lipid sparing may play a role in the effect, in addition to de novo lipogenesis. Finally, approximately a quarter of ingested fructose can be converted into lactate within a few of hours. The reviewed data provides a profile of how dietary fructose is utilized in humans.Nutrition & Metabolism 10/2012; 9(1):89. DOI:10.1186/1743-7075-9-89 · 3.36 Impact Factor