The cyclocross peloton will travel to the Normandy region for the next round of the World Cup in Flamanville, France, on Sunday, and riders have been given a warning by the management of Toon Aerts and Shari Bossuyt.
Both riders tested positive for the cancer drug Letrozole after racing in the region. Aerts' positive came after the Flamanville World Cup on January 16, 2022. His out-of-competition doping control three days later turned up positive for the drug's metabolites.
Bossuyt was racing at the Tour de Normandie Féminin on March 19, 2023, when she gave a doping control sample that also turned up positive for metabolites of the drug.
The two riders are both represented by Yannick Prévost of ISEA Sport Management, who sent a warning to other riders on their roster, including Michael Vanthourenhout and Toon Vandebosch, according to Sporza.
The letter advised riders not to eat any local dairy products and to bring their own food from Belgium.
Aerts and Bossuyt hypothesised that their positives came about because dairy farmers may be using Letrozole to synchronise cows' estrus for fertilization.
"We still base this on our hypothesis that Toon and Shari tested positive after consuming dairy products in Flamanville. Their files show too many similarities to neglect this.
"Letrozole Metabolite may be present in cow's milk. Our hypothesis is that their positive test is due to this, but this has not been confirmed by laboratory analyses," the management company said.
Letrozole is banned by WADA because it can be used to reverse the feminizing effects of anabolic steroids.
A 2019 study showed that hair analysis can be used to distinguish between long-term use for doping and inadvertent ingestion.
Toon Aerts let his hair grow for such an analysis but was unable to clear his name and was given a two-year ban, which expires just before the end of this season.
He is reportedly close to signing with the Deschacht-Hens-Maes team, according to Het Nieuwsblad.
Bossuyt is still pleading her case. She was to partner with Lotte Kopecky on Belgium's team for the Madison at the Olympics, but her participation is pending the outcome.
