© 2022 WRVO Public Media
Your Source for NPR News
Play Live Radio
Next Up:
Available On Air Stations

How a journalist debunked a decades old health tip

Catherine Loper

The recommendation to floss was removed from the federal dietary guidelines in January after 25 years, due to a lack of evidence to back up the suggestion.

Jeff Donn, the Associated Press reporter who broke the story in August, found the first thread to pull after a routine meeting with his son’s orthodontist when the doctor asked if Donn wanted a good tip.

This week on “Take Care,” Donn, a 30-year staffer for AP and a 2012 finalist for the Pulitzer Prize for national reporting, shares his story about how he debunked flossing as well as talking to government agencies, which led to the recommendation being removed.

Donn’s son’s orthodontist shared with him that there was in fact no good evidence that dental floss helps prevent cavities and gum disease. The reporter kind of shrugged off the comment in the moment, but his interest was piqued.

As he began his own research, he found that there were dentists who shared similar frustrations about the assumption that dental floss was proven to have the benefits which were claimed. But, Donn also found some who had never really thought about it.

“There are other dentists who have just bought into what they were taught in dental school and never really did any of their own research,” Donn said. [They] were true believers and believe that the evidence is there when the evidence in studies would suggest that it’s not there.”

Dentists offered a number of reasons to Donn about why studies were ineffective. Many were only run for a period of time as short as a couple weeks, while cavities and gum disease can take a long time to develop. Also, he found a study where the 25 people tested used floss just once.

Donn says the studies show no long-term benefits even when floss is used properly. That being said, dentists told Donn many people in flossing studies do not floss properly and even some oral health professionals do not know how to properly use it.

When Donn went to leading professionals in oral health and floss manufacturing, he asked them to send him the best evidence they had to back up use of the floss. Most sent him studies such as the ones which ran only two weeks or tested each person after one use.

The federal Department of Health and Human Services and Department of Agriculture, which each play a role in setting the guidelines, were other places he went for evidence because the guidelines are required by law to be backed up by the best science available. Neither could find anything, even after he made formal requests for the files backing up the suggestion.

This realization, which Donn’s investigation prompted, led to the removal of the recommendation.

“They dropped the recommendation for dental floss and the very next day wrote me a letter in reply to my Freedom of Information request saying, ‘Sorry. There is no scientific back up. We never researched the issue,’” Donn said.

Donn was not all that surprised by the change. He had previously heard from members of the scientific advisory committee that update the guidelines who told him things such as, “We don’t recall ever talking about dental floss” or “Dental floss? I didn’t know that was in the dietary guidelines.”

Nevertheless, the guidelines had been altered and Donn had played a large role in making it happen.

Donn says he never meant to affect individual’s personal decisions about floss usage. He believes that is a decision for them to make with consultation with their doctors. He says his job is to find stories important to the public and inform people. If he comes across a widely accepted idea that is wrong, such as this one, it is also his job to challenge it.

“There’s something I’ve learned about dental floss that it’s sort of intimate, yet people can talk about it,” Donn said. “There’s something that sort of often is humorous in people’s minds about it. [It’s] a little piece of string that you pass through your teeth.”