The National Football League is warning players not to eat a lot of meat in countries where anabolic steroids are used by the cattle industry.
“There is evidence that some meat produced in China and Mexico may be contaminated with clenbuterol,” a statement to players sent by the NFL’s drug-testing program's administrator read, according to ESPN.
The memo, which included the logo of both the league and the NFL Players Association, went on to note, “consuming large quantities of meat while visiting those particular countries may result in a positive test.”
Clenbuterol, an anabolic steroid banned under the league’s performance-enhancing drug (PED) policy, was the substance that caused Houston Texans’ linebacker Duane Brown to fail a test last season.
Brown, whose 10-game suspension was overturned in April, claimed that the positive result came from a bye-week trip to Baja California, during which he ate 10 hamburgers and two steaks, according to the Washington Post.
Ranchers in Mexico have been known to feed clenbuterol to livestock to help increase meat yields, even though it is prohibited.
In Brazil, Olympic organizers will also monitor meat-eating athletes.
Mexico's national sports commission, Conade, said Wednesday that coaches are keeping a special watch on meat supplied to athletes ahead of the Rio de Janeiro Olympic games this summer.
"We should be conscious and careful about the kind of meat that is selected" for athletes, said Conade director Alfredo Castillo. He said organic beef, chicken, fish and pork could be explored for somewhat safer alternatives.
The steroid, which boosts metabolism and burns fat, has caused problems for Mexican athletes before. In 2011, five national-team soccer players tested positive and were banned from playing in the CONCACAF Gold Cup, the championship of North and Central America and the Caribbean.
FIFA tested the players at the 2011 Under 17 World Cup, which was held in Mexico, and found that most of them had traces of clenbuterol in their system.
Mexican authorities inspected 200 slaughterhouses in 2015 and found the steroid in livestock at 58 of them. Those slaughterhouses were slapped with suspensions.
"Players are warned to be aware of this issue when traveling to Mexico and China," the drug policy program’s memo read. "Please take caution if you decide to consume meat, and understand that you do so at your own risk."
The message – which was tweeted out by various players, including Arizona Cardinal Patrick Peterson – concluded, "Players are responsible for what is in their bodies."
Brown will be heading back to Mexico on an official capacity when the Texans play the Oakland Raiders on Nov. 21 in Mexico City.
Presumably, he will choose to eat more chicken or pork this time.
The Associated Press contributed to this report.