This popped up under politics, but seems to be a topic that fits better either here, or under "Professional Cycling".
Runner says tainted burrito led to test for banned substance
Houlihan made a list of all the food she ate leading up to a Dec. 15 test that produced the adverse analytical finding for the anabolic steroid.
“We concluded that the most likely explanation was a burrito purchased and consumed approximately 10 hours before that drug test from an authentic Mexican food truck that serves pig offal near my house in Beaverton, Oregon,” Houlihan wrote. “I notified the AIU that I believed this was the source."
... the anabolic steroid nandrolone. She said she's since learned it has “long been understood by WADA (World Anti-Doping Agency) that eating pork can lead to a false positive for nandrolone, since certain types of pigs produce it naturally in high amounts. Pig organ meat (offal) has the highest levels of nandrolone.”
Drugs In Sport: Nandrolone may be in food chain
Apparently an old article from September 1999.
The sprinters Linford Christie, Dougie Walker and Gary Cadogan have all recently been cleared of drug abuse by their national governing body, UK Athletics, despite having tested positive for nandrolone.
AIU rejects pork fat defence for nandrolone AAF
James Kibet has been sanctioned with a four year ban... Studies suggest that pork fat can contain significant quantities of nandrolone, and the Kenyan said he had ingested pork fat syrup up to three times a day whilst in Italy for the Corsa dei Santi 10km race, where he returned his AAF on 1 November 2019.
Kibet had ingested pork fat and used it as a body lotion, which he argued is a medicinal custom in his home country of Uganda.
That sounds like A LOT OF PORK FAT