CrossRef Competing interests The authors declare that they have no competing interests. Authors’ contributions AP was the primary author and carried out data collection, analysis of blood samples, and statistical analysis. JG and AT helped collect data. AB assisted with statistical analysis. JL and MB assisted with analysis of POMS and

SST data. MG and RK assisted with manuscript preparation. buy Lumacaftor MB, JO, SS, and CR assisted with analysis of blood samples. All authors read and approved the final manuscript.”
“Background Carbohydrate ingestion prior to exercise has been shown to affect metabolic responses and performance [1]. It is suggested that carbohydrate feeding prior to exercise provides additional supplies for oxidation, results in increased muscle glucose uptake and reduced liver glucose output during exercise [2] and the enhanced blood glucose availability may preserve muscle glycogen stores [3]. β-endorphin is one of the peptides that has been suggested to

play a role in glucose metabolism at rest [4, 5] and during exercise [6–9]. β-endorphin is an opioid peptide representing the C-terminal 31 amino acid residue fragment of pro-opiomelanocortin. Data indicates that stress is a potent inducer of β-endorphin release and it is well known that exercise of sufficient intensity and duration elevates its circulating concentrations [10–13]. The fact that both central and peripheral β-endorphin levels appear to change under hyperglycemic or hypoglycemic conditions suggests that endorphins are implicated in the regulation MG-132 price of glucose homeostasis [4, 13]. Specifically, β-endorphin infusion attenuated glucose decline during prolonged exercise [6, 7, 9, 14, 15], a result that was accompanied

by marked changes in glucoregulatory hormones such as insulin and glucagon whereas opiate blockade produced opposite results [6, 14, 15]. Thus, there is enough data to support that β-endorphin could be affected by differences in blood glucose availability as the ones produced by the consumption of different O-methylated flavonoid glycemic index (GI) foods. Glycemic index ranks foods according to their effect on blood glucose levels compared to a reference food [16]. There are several studies that examined the effects of foods of various GI values prior to exercise with inconsistent results being reported in regards to performance [17–20] and carbohydrate utilization during exercise [17, 19]. Exercise performance has been positively affected by low glycemic index (LGI) food [17] and remained unaffected by high glycemic index (HGI) food [18, 19]. Even though there is inconsistency regarding the benefits of the ingestion of foods of varying GI on exercise performance, several findings indicate that ingestion of LGI foods may be more suitable over HGI consumption prior to prolonged exercise because they enhance carbohydrate availability during exercise [21, 22].