A. Libby, M. Bailey, E. Ehnert, K. Priest, E. Donovan

Gonzaga University, Spokane, WA

Exogenous ketone supplements, in both salt and ester form, have gained popularity among recreational and elite athletes as they are hypothesized to serve as alternative energy sources and potential performance enhancers. PURPOSE: To directly compare ketone salt (KS) and ester (KE) supplements against a non-caloric placebo (PLA) by determining rate of appearance of beta-hydroxybutyrate (BHB) in the blood, impact on blood glucose levels, and respiratory exchange ratio (RER) in healthy college-aged individuals. METHODS: Recreationally active college-aged individuals (n=5; 19.6 ± 1.1yrs) were recruited to participate in three randomized experimental trials, 48 hours apart, in which they received either PLA, KS, or KE in liquid form presented in an opaque bottle. Dosing of ketone supplements was normalized to body weight at 300 mg/kg and flavor matched. After baseline measurements, respiratory gases, blood BHB and blood glucose were collected at ten minute increments for one hour. Data were analyzed using two-way repeated measures ANOVA to compare blood BHB, glucose, and RER over the trial duration. RESULTS: At baseline there were no differences between KE, KS and PLA for any outcome. Individuals in the KE group had significantly elevated BHB levels compared to PLA and KS groups at both 10m and 20m (p<0.05). Beginning at 30m, each group differed significantly from one another for the remainder of the trial (p<0.05), with KE inducing significantly elevated BHB levels greater than both groups (p=0.03) peaking at 2.7 mmol/L. No significant differences (p>0.05) were found between groups for blood glucose at any point during the trial, however there was a non-significant decrease of blood glucose levels in both the KS and KE groups beginning at 40m. No significant differences were observed between groups for RER. CONCLUSION: Our findings indicate that KE supplements elevate blood BHB levels significantly more than KS supplements despite the doses being normalized to body weight. Neither KE nor KS supplements appeared to have an effect on blood glucose levels or RER throughout the trial. Future research should investigate the potential performance effects of KE versus KS supplements using our findings to control for BHB rate of appearance with each ketone form to inform experimental protocols.

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