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A US runner claims a pork burrito caused a positive drug test. Research shows that’s possible but unlikely

Shelby Houlihan was suspended for four years after testing positive for the banned substance nandrolone.
Credit: AP Photo/Charlie Neibergall, File
In this Sunday, July 28, 2019, file photo, Shelby Houlihan crosses the finish line as she wins the women's 5,000-meter run at the U.S. Championships athletics meet, in Des Moines, Iowa.

The Summer Olympics in Tokyo, Japan, are a month away after being delayed a year due to the COVID-19 pandemic. That means athletes are competing to qualify for the international event.

One runner, Shelby Houlihan, who holds the women's American record in the 1,500-meter and 5,000-meter races, will not be competing in Tokyo this year. Houlihan shared in a June 14 Instagram post that she had been banned for four years after she tested positive for an anabolic steroid called nandrolone in December of 2020. In her Instagram post, Houlihan blamed the positive test on a pork burrito she ate “approximately 10 hours before that drug test.”

THE QUESTION

Has consuming pork been linked to elevated levels of nandrolone?

THE SOURCES

THE ANSWER

This is true.

Yes, research has shown a connection between the consumption of pork, particularly non-castrated pork, and elevated levels of nandrolone. However, experts say the consumption of the castrated pork that’s commonly found in the United States would not likely result in a positive test.

WHAT WE FOUND

Nandrolone, also known as 19-nortestosterone, “is a synthetic, anabolic steroid analog of testosterone,” according to the NIH

“Chronic usage is thought to cause an increase in muscle bulk, and can cause an exaggeration of male characteristics and effects related to male hormones,” the NIH says.

Nandrolone is also produced naturally in humans, although at low levels, well below the doping standard set by the International Olympic Committee (IOC). It has been banned by the IOC since 1974, according to a study published in Rapid Communications in Mass Spectrometry.

A 2019 report from the World Anti-Doping Agency (WADA) identified a metabolite of nandrolone, called 19‐norandrosterone, as one of the most common steroids found in athletes. 

In her Instagram post, Houlihan said: “I have since learned that 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.”

There are studies that have examined a potential link between pork and elevated levels of nandrolone. In a study published in 2000, three male volunteers each ate 310 grams, nearly 11 ounces, of edible boar tissue and had their urine sampled before, during and 24 hours after consumption. Urine samples taken 10 hours after boar tissue consumption showed levels of nandrolone above the Olympic doping standard.

“We have thus proved that eating tissues of non-castrated male pork (in which 17β-nandrolone is present) might induce some false accusations of the abuse of nandrolone in antidoping,” the authors of the study concluded. 

Dr. Shalender Bhasin, a professor of medicine with Brigham and Women’s Hospital, said while the participants in the study consumed non-castrated boar meat, almost all of the pork people eat in the US is from castrated pigs, which he says have exceedingly small amounts of nandrolone. 

“People have studied this, that eating the meat of wild boars can result in a positive test within a few hours after eating that meat and it can stay positive for a few hours,” Bhasin said. “But that's not the case in real life because nearly all of the meat that's commercially available, that you might find in a restaurant or in a grocery store, comes from castrated pigs.”

Bhasin said eating meat from a grocery store would not lead to a positive nandrolone test.

“I think that is the question that these types of stories raise amongst athletes: whether they should be fearful of eating meat that might make them disqualified,” Bhasin said. “And the short answer is that it's not possible to fail a doping test by eating meat from a grocery store or eating a regular vegetarian or non-vegetarian diet.” 

A 2006 article published in the British Journal of Sports Medicine examined what could lead to a positive test for nandrolone. The author described the ingestion of non-castrated pig meat as “improbable” because it’s so difficult to find. 

Still, the author warned against eating pig offal before a drug test as a precautionary measure. 

“Although highly improbable, athletes should prudently avoid meals composed of pig offal in the hours preceding the test since the consumption of edible parts of a non‐castrated pig, containing 19‐nortestosterone, has been shown to result in the excretion of 19‐norandrosterone in the following hours,” the author wrote.

In 2003, an expert committee on nandrolone reported to the UK Sports Council that athletes may want to avoid offal.

“We are unable to assess fully the possible risk that consumption of meat may cause a notifiable urine concentration of 19-norandosterone, but we believe that the possibility is remote from eating good quality unprocessed muscle meat from commoner animal species,” the committee concluded. “It may be prudent to avoid offal from boar and horse.”

Houlihan isn’t the first athlete to contend that pork led to a positive nandrolone test. A runner from Kenya, James Kibet, tested positive for nandrolone in November 2019. In his arbitration case, Kibet attributed the positive test to pork fat he believed was contaminated. His four-year suspension was also upheld. 

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