Ketone supplements, intended to boost athletic performance, may actually reduce it, as evidenced by slower cycling speeds in athletes, a study suggests. The research, published in the International Journal of Sport Nutrition and Exercise Metabolism, analysed contradictory findings related to the effectiveness of ketone supplements, which have gained popularity among athletes seeking a competitive advantage. Some previously published studies had shown the supplements improve performance, while others have reported they had no effect or even worsened performance, the researchers said.
Research suggests otherwise, according to experts
Natural ketones can serve as fuels for the brain and muscles. A ketogenic diet - characterised by very low carbohydrate and typically high fat intake - causes the body to produce more organic ketone compounds and increase their use for energy, they said. "One of the main perceived benefits is that ketones may serve as an alternative fuel source during exercise or potentially alter the utilisation of other major fuel such as carbohydrates and fats, and in turn enhance endurance capacity," said Martin Gibala, a professor at McMaster University in the UK. "But our findings suggest that is not the case," Gibala said.
The researchers recruited well-trained endurance athletes who cycled five or more hours per week, selecting them because their athletic performance is consistent from day to day. The experiment was conducted in a lab but simulated race conditions and the participants prepared as they normally would for a cycling competition. Each participant completed two trials that differed only in the drink provided before they completed a 20-minute cycling time trial that closely predicts 40-km race performance. The drinks contained either a ketone supplement or a similar-tasting placebo.
The experiment was a double-blind research
The research was structured as a double-blind study, meaning neither the researchers nor the athletes knew whether the ketone supplement or the placebo was provided. "The main observation from this study was that the speed that the cyclists could sustain during the test was lower after drinking the ketone supplement compared to the placebo," said Devin McCarthy, lead author of the study and graduate student at McMaster.
Researchers said the findings align with their previous work which found ketone supplements increased cardiorespiratory stress during exercise. They are currently investigating responses to varying doses of the supplements at different exercise intensities to better understand how ketones may affect performance, and the potential underlying mechanisms.