Findings in which athletes consumed ketone salts prior to a cycling time trial found they increased fat oxidation during steady state exercise but impaired high-intensity exercise performance.
The team pointed to an average time trial power output was around seven per cent lower (-16 Watts) in those taking ketone supplements.
Ketone salts work by artificially elevating blood ketone levels, forcing the body to rely on burning fat as a fuel.
This is ideal for long-term use, but is not as readily accessible as glucose for quick bursts of muscle activity, which characterise high-intensity workouts, like running a 10k or cycling up a hill rely upon.
"Elevated blood ketones seem to inhibit the body's use of glycogen, the stored form of glucose, and favours burning fat instead," said study co-author Jonathan Little, assistant professor in University of British Columbia’s (UBC) Okanagan's School of Health and Exercise Sciences.
"That means that the body's quick-burning fuel cannot be accessed during high-intensity bursts of activity and athletic performance is dropping off as a result."
Salts vs. esters
Ketone salts have garnered considerable attention as an aid to enhancing physical performance.
Alongside caffeine and lesser known supplements such as hydroxymethylbutyrate (HMB), conjugated linoleic acid (CLA), carnitine, chromium and creatine, these aids are marketed to boost athletic performance.
Despite their popularity, definitive scientific proof of their effectiveness is somewhat lacking or contradictory.
While ketone salt supplements are available in Europe, ketone esters, which are the raw beta-hydroxybutyrate (BHB) ketone itself minus any salts or other compounds bound to it, have resonated more with athletes with claims of enhanced muscle recovery and slower glycogen loss.
In its raw form the body is purported to take up the ketones more quickly, possibly raising blood ketone levels to a higher level.
Ketone ester supplements became commercially available earlier this year, with the launch of a Ketone Ester (D-beta-hydroxybutyrate and D 1,3-butanediol) sports drink created by US company KetoneAid.
Other companies keen to make headway in this space include Oxford University’s spin-off company, T∆S Ltd, created to promote its own ketone drink called ΔG.
Dr Little’s study enrolled ten healthy adult males with similar athletic abilities and body mass.
After a period of fasting, they were asked to consume either beta-hydroxybutyrate ketone salts (KetoForce) or a flavour-matched placebo, in a randomised order. The subjects then performed a cycling time trial.
Power output on the day participants consumed ketone salts was seven per cent lower than on the day when they consumed the placebo. In addition, total fat oxidation was greater in the ketone group versus control.
“Often these supplements are marketed as a means of improving athletic performance but in this case, the research tells a very different story," said Dr Little.
"On top of that, the long-term impacts of artificially increasing blood ketone levels--essentially tricking the body into thinking it is in a state of starvation--is completely unknown."
"I hope this helps athletes navigate the science of supplements rather than relying on label marketing alone."
Speaking to NutraIngredients late last year, Dr Kieran Clarke, professor of physiological biochemistry at the University of Oxford and co-founder of T∆S Ltd commented on the interest she had received for this drink.
“I would say I’ve got at least one email a day [asking to buy the drink], if not more, for years and years,”she said. “And I keep them all and I always answer them and I promise I will tell them when it becomes available.”
The drink, protected by 24 patents, are currently seeking EU novel food approval from the UK’s Food Standards Agency (FSA) since 2011, having received US approval back in 2014.
Source: Applied Physiology, Nutrition, and Metabolism
Published online ahead of print: doi.org/10.1139/apnm-2016-0641
“Nutritional ketone salts increase fat oxidation but impair high-intensity exercise performance in healthy adult males.”
Authors: Trevor O’Malley, Etienne Myette-Cote, Cody Durrer, Jonathan P. Little