Cycling: Ketones, Substances That Divide The Peloton!

Increasingly popular among professional cyclists, these dietary supplements are believed to significantly improve athletic performance despite the lack of scientific evidence to this effect.

They have invaded the peloton and carry with them their share of questions and suspicions of doping. Ketones, substances whose effects are still poorly understood, crystallize a heated debate in the world of professional cycling. Simple food supplements for some, they are accused of significantly improving performance by others.

Ketones, or ketone bodies, are organic compounds produced naturally by the liver when the human body is subjected to extreme conditions. Deprived of carbohydrates, the body lacks fuel secretes ketones which will take over by nourishing the muscles and the brain. “It is a natural mechanism that we find in people who go on hunger strike”, illustrates Jacky Maillot, doctor of the Groupama-FDJ cycling team. These substances, synthesized in the laboratory, are now widespread in all endurance sports. In the peloton, some runners consume them in the form of gels or drinks. “The idea is to bring ketones to the body to save the athlete's carbohydrate stock, who can then use these carbohydrates at the end of the stage,” explains the sports doctor.

A Simple Food Supplement?

Ketones would therefore improve athletic performance and some teams do not deprive themselves of it. During the Tour de France 2019, the Dutch team Jumbo-Visma publicly admits their use. Julian Alaphilippe and his Belgian formation Deceuninck Quick-Step also. “It is a food supplement” which “is part of my nutritional plan”, then confides the French runner.

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While the two-time world champion considers their use legitimate, this is not the case for all members of the peloton. In particular, renowned French riders like Romain Bardet. In an interview with the newspaper”The Team” Monday, December 13, the tricolor climber reiterated his wish to see the authorities legislate on ketones, which he accuses of generating “a two-speed cycling” between the teams who forbid their use and those who consume it. Similar speech given by Arnaud Démare, who, if he refuses to talk about doping, “wonders about the peloton” and regrets the “inequalities” induced by the use of ketones, in a passage from his book published in November.

Lack Of Scientific Evidence

However, to date, no scientific study has proven that ketones significantly improve athletic performance. “In 2019, a Belgian study by Professor Hespel spoke of a performance improvement of 15%,” says Jacky Maillot. But this study was not based on high-level athletes and all those carried out thereafter contradict this figure. ”

As it stands, scientific research has also not established that the consumption of ketones has proven serious consequences on the health of athletes. ” Minor digestive disorders” have been noticed in some runners according to the sports doctor, who recalls all the same that “scientists do not yet have sufficient hindsight to know possible long-term consequences on health”.

Credibility Issue

These gray areas aren't the only things ketone detractors are concerned about. The use of these still little-known substances revives the old demons of a sport whose image has been permanently damaged by repeated doping scandals. “We call for a ban on ketones to remove suspicion from cycling. It is an issue of credibility ”, proclaims Roger Legeay, president of the Movement for credible cycling (MPCC). Ten World Tour teams, including four French, join the association and ban ketones while nine others use them.


As the debate grows, the International Cycling Union (UCI) has launched a study to determine if ketones actually lead to improved performance. Xavier Bigard, medical director of the UCI, nevertheless recalled that a ban on ketones “seems complicated in the current state of things”. ” We must above all bring rationality to this debate and stick to scientific evidence,” insists Jacky Maillot. The rules are not set in stone.

Non-Doping Substances According To The Criteria Of The World Anti-Doping Agency

While it advises against the use of ketones, the International Cycling Union (UCI) is not the only body to authorize these controversial substances. The World Anti-Doping Agency (WADA) has also not put ketones on the list of banned products. A product may be subject to a ban if: “It has the potential to improve or actually improve athletic performance; it is a proven or potential risk for the health of the athlete; it is contrary to sportsmanship ”. Since ketones do not meet at least two of these three criteria, they cannot be banned by WADA.

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