An American middle-distance runner has been banned from competitive running for four years following a positive drug test for anabolic steroids, which are infamously used to enhance performance illegally in sports. However, she is now claiming that the drug test is actually wrong – she was not under the influence of performance-enhancing drugs, but a humble pork burrito. 

Shelby Houlihan announced her suspension recently after testing positive for nandrolone, the most commonly-used androgen and anabolic steroid (AAS) in the world and one with a history stained with illegal use in professional athletes. It was banned from the Olympics in 1974. 

Houlihan holds a strong stance that she has never heard of – let alone taken on a regular basis – nandrolone, as she describes in her Instagram post. But an investigation from the Athletics Integrity Unit (AIU) informed her that a routine drug test had highlighted a positive for nandrolone, which they called an Adverse Analytical Finding, and was grounds for immediate suspension.  

So Houlihan researched nandrolone and discovered that the World Anti-Doping Agency (WADA) has identified detectable levels of the steroid within pork, owing to a natural ability of pigs to create nandrolone in high quantities, and has recommended that false positives could occur as a result. Specifically, the organs of pigs (used to create offal), contain the highest levels of nandrolone. 

After creating a food diary, Houlihan realized she had eaten offal from a Mexican food truck, contained within a burrito. The levels of nandrolone in her sample matched (according to her) the levels found in those that had consumed offal. She then underwent polygraph and hair testing, which suggested there was certainly no regular use of the steroid and instead likely just one ingested source – whether that be in drug form or burrito form. Despite challenging the Court of Arbitration for Sport, which settles disputes in sports and the Olympics, with the new information, her appeal was denied. 

So, is it possible a pork burrito could lead to a false positive for a Schedule III drug? The science says yes. 

A study in 2000 discovered that concentrations of steroids of up to 7.5 micrograms per liter could be detected 10 hours after boar tissue consumption, with levels returning to normal at around the 24-hour mark. Houlihan claims the burrito was eaten 10 hours before her drug test, and with her results matching the concentrations on the study, according to her, it is within reason that the offal could be the culprit. Alongside this, a WADA-commissioned study in 2018 discovered metabolites originating from steroids can be found in detectable quantities from urine samples, following ingestion of non-castrated pig meat.  

Other studies have identified dietary sources of illegal substances in sports, including poultry and eggs introducing minute amounts of clomiphene (an anti-estrogenic substance that is used in testosterone replacement therapy) in drug samples. 

Based on limited evidence, it seems entirely plausible Houlihan’s reasoning could check out. Regardless, it appears the athlete will not be attending the Tokyo Olympics as a result, but her case certainly raises the need for more comprehensive study into the impacts of diet on drug testing.