Pre-exercise galactose and glucose ingestion on fuel utilization during exercise

O'Hara, J.P., Carroll, S., Cooke, C.B., Morrison, D.J. , Preston, T. and King, R.F.G.J. (2013) Pre-exercise galactose and glucose ingestion on fuel utilization during exercise. Medicine and Science in Sports and Exercise, 44(10), pp. 1958-1967. (doi: 10.1249/MSS.0b013e318258bf85)

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Purpose: This study determined the effect of ingesting galactose and glucose 30 minutes prior to exercise on exogenous and endogenous fuel utilization during exercise. <p/>Methods: Nine trained male cyclists completed three bouts of cycling at 60% Wmax for 120 minutes, following an overnight fast. Thirty minutes prior to exercise the cyclists ingested either a fluid formulation containing placebo, 75g of galactose (Gal) or 75g of glucose (Glu) to which 13C tracers had been added, in a double blind randomized manner. Indirect calorimetry and isotope ratio mass spectrometry were used to calculate fat oxidation, total carbohydrate (CHO) oxidation, exogenous CHO oxidation, plasma glucose oxidation and endogenous liver and muscle CHO oxidation rates. <p/>Results: Peak exogenous CHO oxidation was significantly higher following Glu (0.68 +/- 0.08g[middle dot]min-1, P<0.05) compared to Gal (0.44 +/- 0.02 g[middle dot]min-1), however mean rates were not significantly different (0.40 +/- 0.03 vs. 0.36 +/- 0.02 g[middle dot]min-1, respectively). Glu produced significantly higher exogenous CHO oxidation rates during the initial hour of exercise (P<0.01), while glucose rates derived from Gal were significantly higher during the last hour (P<0.01). Plasma glucose and liver glucose oxidation at 60 minutes of exercise were significantly higher for Glu (1.07 +/- 0.1 g[middle dot]min-1, P<0.05 and 0.57 +/- 0.08 g[middle dot]min-1, P<0.01) compared with Gal (0.64 +/- 0.05 g[middle dot]min-1 and 0.29 +/- 0.03 g[middle dot]min-1, respectively). There were no significant differences in total CHO, whole body endogenous CHO, muscle glycogen or fat oxidation between conditions. <p/>Conclusion: The pre-exercise consumption of Glu provides a higher exogenous source of CHO during the initial stages of exercise, but Gal provides the predominant exogenous source of fuel during the latter stages of exercise and reduces the reliance on liver glucose.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Preston, Professor Tom and Morrison, Dr Douglas
Authors: O'Hara, J.P., Carroll, S., Cooke, C.B., Morrison, D.J., Preston, T., and King, R.F.G.J.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Medicine and Science in Sports and Exercise
Publisher:The American College of Sports Medicine
Published Online:01 October 2012

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