In 2013, she attended a Gordon Research Conference where microbiome researcher Dunedin-born Rob Knight of the University of California, San Diego (UCSD), gave a talk about the American Gut Project, which invites people to send in stool samples for analysis.
The project combines data from those samples with the participants' answers to survey questions about disease history, lifestyle, diet, and more, to determine the most important factors in shaping a person's microbiome. "As soon as Rob got there and gave his spiel, and said, 'Get your own microbiome sequenced for $89,' I signed right up."
Petersen recalls the test results she got back later that year: "I had a horrible microbiome—very, very bad." All those years on antibiotics, she says, "I had no idea that essentially my entire gut microbiome was being wiped out."
Not only did she lack many of the beneficial bacteria commonly harbored by people without symptoms of disease, but the results also showed that her gut had been colonized by several pathogenic strains that she'd worked with in her lab.
Peterson is a research scientist at the Jackson Laboratory for Genomic Medicine in Farmington, Connecticut, United States and now heads up an initiative called the Athlete Microbiome Project, in which she compares stool samples of elite cyclists to amateur bikers.
Her findings strikingly shine a light on a handful of microorganisms that apparently separate the guts of elite athletes from average people.
The most important, perhaps, is Prevotella. Not typically found in American and European gut microbiomes, Prevotella is thought to play a role in enhancing muscle recovery.
"In my sampling, only half of cyclists have Prevotella, but top racers always have it," she told Bicycling. "It's not even in 10 percent of non-athletes."
Peterson reports she hosts Prevotella in her own gut - but not naturally. In fact, she might be the first case of "poop doping," thanks to a fecal transplant she administered herself three years ago. Her donor? Another elite athlete.
Peterson didn't decide on the fecal transplant solely to enhance her performance during her mountain bike races, but to cure a host of symptoms that have affected her since she was a child and contracted Lyme disease.
"I had no microbes to help me break down food, and I had picked up bugs in the lab where I was working because my system was so weak and susceptible," she told said.
But, she continued, "I couldn't find a doctor who could help me" since in the United States, fecal transplants are only performed to treat serious cases of Clostridium difficile, a disease that causes chronic diarrhea. And so Peterson went rogue.
Peterson detailed her decision to perform the "risky" procedure on herself on the podcast "Nourish Balance Thrive" in 2016.
Read more: Nourish Balance Thrive podcast
She admitted to thinking it was a "bad idea" at first because if not done with proper screenings of both parties, it could worsen a person's problems. But through chance, she came across a donor, an elite long-distance racer, who had his microbiome mapped and screened after a case of food poisoning, which showed he was otherwise healthy.
So Peterson took antibiotics to wipe out her own gut bacteria and essentially performed a reverse enema.
"I just did it at home," she said of the February 2014 procedure. "It's not fun, but it's pretty basic."
Within a month, Peterson said, she began feeling better than she'd felt in years.
"I had more energy than I knew what to do with," she told the same podcast last year. "Like everything just changed."
Peterson, who's in her mid-30s, said before her transplant she was having trouble just training on her bike; just months later, she said she began winning pro races.
More importantly for her life's work, however, her own success with the fecal transplant gave her the idea to start the Athlete Microbiome Project, for which she rounded up 35 of her cycling friends, according to the Scientist magazine, to kick off her research.
Along with Prevotella, Peterson said she also identified another possibly performance-enhancing microbe called Methanobrevibacter archaea, which Peterson found to be more prevalent in the samples from elite athletes. This bacteria's function is also opaque, however, Peterson told the Scientist, "it allows your entire gut microbiome to work more efficiently" by more effectively breaking down complex carbohydrates in the gut.
Peterson said it's too early to make any concrete conclusions about how the microbiome affects performance, but she's convinced there's enough evidence to suggest it does make a difference.
"What we're learning is going to change a lot for cyclists as well as the rest of the population," Petersen told Bicycling magazine. "If you get tested and you're missing something, maybe in three years you'll be able to get it through a pill instead of a fecal transplant. We've got data that no one has ever seen before, and we're learning a lot. And I think I can say with confidence that bacterial doping . . . is coming soon."
