Jumbo-Visma's team boss Richard Plugge has confirmed his squad have been using ketones, a "miracle drink" dietary supplement that aids recovery for endurance athletes, during the Tour de France 2019, where the Dutch team have so far won four stages.
Plugge noted that the substance, which are used just like other vitamins, is not on the prohibited list and is also being used by other teams, with seven of the 22 squads at the 2018 reported to have benefitted from its use.
Last year a brand teamed up with the inventor of the product saying it had collected customers amongst WorldTour teams.
Jumbo-Visma confirmed their use of ketones to Dutch newspaper De Telegraaf, who also report that a study by KU Leuven says the substance can improve performance by 15 per cent.
A test was conducted by Professor Peter Hespel on people tasked with using the substance whilst riding a mini Tour de France who experienced an "unprecedented" recovery as well as their performance capacity increasing considerably.
The supplement is not on WADA's (World Anti-Doping Agency) list of banned substances and is allowed to be used, with riders ingesting it by mixing it into their drinks.
Hespel also revealed to Flemish broadcaster VRT that a pro rider told him he had ridden a dozen Tours de France, one on ketones, with that one on ketones resulting in his heartbeat hardly dropping when he got to Paris compared with when he rolled out in the prologue three weeks earlier.
Professor Peter van Eenoo, whose lab has been alerted to reports of the doping agent Aicar being used in the peloton, says there is nothing wrong with the use of ketones.
"The drug is not on the doping list, because the investigation into the side effects is still in its infancy," he said. "As long as the negative effects cannot be demonstrated immediately, it will not be on the doping list either. I assume that many top athletes use ketones. The drug is available and more and more sports doctors and physiologists recommend it."
However, one team who are not benefitting from ketones is Sunweb, who say there is no real effect of using ketones. "We think there should be more clarity about the effects of this medicine on the health of the athlete in the long term," said the German team's doctor, Anko Boelens.
"In addition, there is much uncertainty about the efficacy. There are even studies that show that it has a negative effect on sports performance. That the remedy would only be good for recovery. We want to be sure that we will not harm our riders," he added.
Ketones were created by researchers at the University of Oxford, who were tasked by the United States Army to create the most efficient fuel for troops heading into battle.
Speaking on his podcast about ketones, Lance Armstrong said: "It's commonly known that usage of ketone esters (chemical compounds) is prevalent in the peloton.
"It's totally legal, I'm not trying to expose anybody here. But the use of ketone esters is there.
"Ketones are essentially the third fuel source. The body has fat, sugar and ketones. And it’s taken us a long time to perfect the ketone ester that you can drink.
"The taste is horrible, extremely expensive. But it’s gotten to a place where it’s less expensive and somewhat drinkable."
On the other side of the aisle, the doping agent Aicar, a muscle-enhancing and fat-burning drug, is believed to be back in the professional peloton at the Tour de France 2019, with anti-doping agencies put on alert after tip-offs from prominent, yet anonymous, figures within the world of cycling.
These claims have been made in Dutch newspaper De Telegraaf, with a WADA-associated (World Anti Doping Agency) lab confirming it was urged by an individual involved in anti-doping at the start of June to accelerate its investigation into Aicar, as a number of people believed the substance was being used by several riders currently taking part in this year’s Tour de France.
Thank you for reading 20 articles this month* Join now for unlimited access
Enjoy your first month for just £1 / $1 / €1
*Read 5 free articles per month without a subscription
Join now for unlimited access
Try first month for just £1 / $1 / €1