Gastrointestinal effects of exogenous ketone drinks are infrequent, mild, and vary according to ketone compound and dose

Abstract

Exogenous ketone drinks may improve athletic performance and recovery, but information on their gastrointestinal tolerability is limited. Studies to date have used a simplistic reporting methodology that inadequately represents symptom type, frequency, and severity. Herein, gastrointestinal symptoms were recorded during three studies of exogenous ketone monoester (KME) and salt (KS) drinks. Study 1 compared low- and high-dose KME and KS drinks consumed at rest. Study 2 compared KME with isocaloric carbohydrate (CHO) consumed at rest either when fasted or after a standard meal. Study 3 compared KME+CHO with isocaloric CHOconsumed before and during 3.25 hr of bicycle exercise. Participants reported symptomtype and rated severity between 0 and 8 using a Likert scale at regular intervals. The number of visitswith no symptoms reported after ketone drinkswas n = 32/60 in Study 1, n = 9/32 in Study 2, and n = 20/42 in Study 3. FollowingKME andKS drinks, symptomswere acute butmild and were fully resolved by the end of the study. High-dose KS drinks caused greater total-visit symptom load than low-dose KS drinks (13.8 ± 4.3 vs. 2.0 ± 1.0; p < .05) and significantly greater time-point symptom load than KME drinks 1-2 hr postdrink. At rest, KME drinks caused greater total-visit symptomload than CHOdrinks (5.0 ± 1.6 vs. 0.6 ± 0.4; p < .05).However, during exercise, therewas no significant difference in total-visit symptom load between KME+CHO (4.2 ± 1.0) and CHO (7.2 ± 1.9) drinks. In summary, exogenous ketone drinks cause mild gastrointestinal symptoms that depend on time, the type and amount of compound consumed, and exercise.