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

© 2019 Human Kinetics, Inc. 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.