22 Aug Stable isotope analysis of deuterium and carbon-13 to simultaneously measure fluid delivery and carbohydrate oxidation during exercise
Many exercise physiologists are interested if carbohydrate drinks influence exercise performance. The benefit of sport drinks to enhance fluid delivery is still controversal. In theory, carbohydrate availability can enhance performance by reducing glycogen depletion, increasing carbohydrate oxidation rates, and preventing acute onset of hypoglycemia.
It has been established that total carbohydrate oxidation rate correlates with power output for strenuous exercise >3 hours. Further, exogenous carbohydrate oxidation rates for single sugars like glucose, may be limited to 1 gm/min due to saturation of the intestinal sodium glucose cotransporter (SGLT1). If this is the case, endogenous carbohydrate sources may limit performance.
Roberts et al. recently published a method to simultaneously measure fluid delivery and exogenous carbohydrate oxidation of commercially available sports drinks. The method involves adding 5 grams deuterium oxide to the beverage administered at 60 minutes during the exercise cycle. Blood samples were collected every 15 minutes to measure deuterium uptake by stable isotope analysis from the fluid ingested. Exogenous carbohydrate oxidation was monitored by collecting breath samples during exercise. Sugars in sport drinks are naturally enriched in carbon-13 compared to other carbohydrate sources so oxidation is measured by stable isotope analysis methods to determine the appearance of 13CO2.
Using this dual approach, Roberts et al. was able to show that a commercially available maltodextrin-fructose beverage improves exogenous carbohydrate oxidation and fluid delivery compared to a maltodextrin alone or placebo drink. These changes support a benefit of maltodextrin-fructose beverages to improve exercise performance.
View a copy of the Roberts et. al. paper: Assessing a sports drink for fluid delivery and carbohydrate oxidation.
Metabolic Solutions offers administration kits, project design assistance and stable isotope analysis to help researchers determine fluid delivery using deuterium oxide (D2O). We offer sensitive methods for measuring deuterium in plasma, urine or saliva with as little as 15-25 µl of sample.
The technique for collecting breath is quite easy. View our breath collection instructions.
Please contact us to discuss your research needs.