Gut Check: Study Raises Questions About at Home Microbiome Testing
For years, Diane Hoffmann, JD, MSc the Jacob A. France Professor of Health Care Law at the University of Maryland Francis King Carey School of Law and director of the Law and Health Care Program, had a suspicion she couldn't prove. As part of an NIH research grant, she had spent more than a half decade studying the direct-to-consumer gut microbiome testing industry, reviewing dozens of company websites, surveying clinicians and tracking the regulatory gaps that left consumers with almost no protection.
Diane Hoffmann and Jacques Ravel
The tests have become increasing popular as people seek to optimize their health in numerous ways, including taking a peek into their gut health. Many have changed their diets, bought supplements or sought medical advice based on the results.
Now Hoffmann has proof that the tests should be taken with a healthy dose of skepticism.
A study recently published in Communications Biology, which Hoffmann co-authored with Jacques Ravel, Phd, director of the Center for Advanced Microbiome Research & Innovation (CAMRI) and assistant dean for Research Advancement at the University of Maryland School of Medicine (UMSOM) and scientists from the National Institute of Standards and Technology (NIST), found that when researchers sent three identical stool samples each to seven direct-to-consumer gut microbiome testing companies, the reports came back with inconsistent results that looked nothing alike. Researchers attributed this to their different collection methods, laboratory protocols and data analysis pipelines. In some cases, the same sample was classified as healthy by one company and unhealthy by another. The number of bacterial species identified ranged from a few dozen to several hundred.
"The hype about these products doesn't match the evidence," said Hoffmann. "These tests often have limited evidence behind them. They don’t provide standardized results and they shouldn’t inform clinical decisions or even basic dietary recommendations.
"The marketing can be questionable, and consumers can end up misinterpreting or overtrusting results that aren't very reliable," she added.
Hoffmann said her time spent on legal research into microbiome regulation prompted the scientific collaboration with Ravel and the NIST researchers. She had studied how companies market these tests, reviewed their claims online and surveyed clinicians whose patients were bringing in the results. What she found troubled her.
"Clinicians often can't explain the results to their patients," Hoffmann said. "And because these companies produce a very glossy, professional-looking report, patients sometimes trust that report more than they trust their doctor."
She described a particularly concerning pattern among parents of children with autism who also have gastrointestinal problems. Desperate for answers, some parents are using these test results to put their children on highly restrictive diets, said Hoffmann.
"In some cases, the doctors felt as if the parents were cutting out certain nutrients in ways that were harmful for the child," Hoffmann said. Doctors also reported a patient undergoing a fecal microbiota transplant at home based on test results. “If done without physician oversight, there is a real risk of serious infection,” she noted.
The study also highlights a regulatory gap. Direct-to-consumer microbiome tests occupy a gray area between medical devices — which can have strict FDA oversight — and general health and wellness products, which do not. Most of these companies have never sought FDA approval as, for the most part, they are not required to do so, and consumers are rarely aware of how little oversight there is of the industry.
Ravel, who has collaborated with Hoffmann for nearly 12 years across multiple NIH-funded projects, said the partnership between the law school and the school of medicine is unusual but valuable.
"This association between scientists and a law professor sounds kind of unusual, but it actually worked really well," Ravel said. "It allowed us to evaluate both the regulatory aspect from a law perspective and the scientific validation required in those different spaces. That's when the idea came up, let's actually do the science to back it up."
Hoffmann said physicians can now share the study directly with their patients to help them understand why those polished reports should raise an eyebrow. Her message to consumers is straightforward.
"Be cautious," she said. "Talk to a physician before making any changes to your diet, your supplements or your medical care based on these results. The evidence just isn't there yet."
