NFL players have been warned about eating foreign meat while traveling in China and Mexico, as it could contain clenbuterol, which is banned by the league as a performance-enhancing substance.
ESPN reported that the NFL's memo to players was possibly triggered by Houston Texans' left tackle Duane Brown, who tested positive for clenbuterol last year after traveling to Mexico during a bye week and eating beef.
Brown, who was facing a 10-game suspension, was cleared by the league in April after an investigation that reportedly lasted months.
The Los Angeles Times reported that during the investigation, Brown showed the league receipts for 10 hamburgers and two steaks purchased during the trip.
"Clenbuterol is a supplement occasionally used by cattle farmers to accelerate growth,"
the website Deadspin explained. "It's banned in the [European Union], Mexico, and the USA, but it's apparently still used commonly enough in Mexico that there have been two recent incidents of team-wide clenbuterol positives in the country. Authorities were able to source the clenbuterol to tainted meat in both cases."
ESPN wrote that in 2011, FIFA found that some players participating in the U-17 World Cup in Mexico tested positive for traces of clenbuterol in their systems.
Several players, like Arizona Cardinals defensive back Patrick Peterson, made the NFL's newest memo public by posting it to Twitter on Tuesday.
"Consuming large quantities of meat while visiting those particular countries may result in a positive test for clenbuterol in violation of the [NFL Policy on Performance-Enhancing Substances]," said the posted memo.
The Los Angeles Times reported that the memo comes after several members of the Oakland Raiders participated in fan activities in Mexico City connected with the NFL draft last week. The Times added that the NFL has scheduled regular season games in Mexico and China.
The Houston Texans will play the Raiders in Mexico City Nov. 21 and the Los Angeles Rams will play against an unnamed opponent in China in 2018, wrote the Times.