The influence of high fructose corn syrup on endurance exercise metabolism
Athletes are advised to ingest adequate amounts of carbohydrate (CHO) prior to competitions, during exercise, and after to replenish glycogen storages. Performance outcomes can be determined by the amount, timing, and sources of CHO ingested. High fructose corn syrup (HFCS) is thought to be one of the main contributors in the development of obesity and chronic disease, therefore making this CHO source controversial. The study purpose was to determine if a HFCS-sweetened beverage is an acceptable CHO source for prolonged moderate intensity exercise by determining its effects on substrate metabolism during exercise when compared to a dextrose-sweetened beverage (DEXT). Eleven (6 male, 8 female: Mean±SD; 24 ± 3.9 yrs, 71.8 ± 12.5 kg, 173.8 ± 9.5 cm) active healthy adults volunteered to participate in for this study. A baseline blood sample was drawn prior to ingesting half of a 400 mL beverage sweetened with 50 grams of HFCS or DEXT 15 min prior to a 120 min cycle and the other half was consumed 10 min of exercise. This was a randomized, double-blinded study. Blood was collected at -20, 58, and 140 min, tested for glucose, lactate, hemoglobin and hematocrit, then coagulated for 20 min, centrifuged for 10 min for serum separation and analyzed for lipids. Respiratory exchange ratio, HR, and RPE were collected at 20, 50, and 115 min during exercise. Treatment interaction effects were determined using repeated measures ANOVA and a one-way ANOVA, with a Tukey (HSD) post hoc test (alpha level < 0.05). All statistics were mean ± SD. There were no significant time by treatment interactions or main treatment effects for any dependent variable RER (p=0.996), triglycerides (p=0.451), CHOL (p=0.230), LDL (p=0.875), HDL (p=0.753), VLDL (p=0.439), glucose (p=0.802), HR (p=0.749), RPE (p=0.719), or lactate (p=0.065). However, there was a significant time effect identified for decreasing RER, increasing HR and RPE that were not related to the treatments, but the physical needs of exercise. In conclusion, the current study demonstrates an acute 50 g dose of HFCS at the beginning of prolonged moderate intensity exercise does not induce hypertriglyceridemia and is an adequate CHO source for supplementation.