Mouthwash May Trigger Diabetes—If You Use Way, Way Too Much of It

Update | A new study claims very, very frequent mouthwash use is associated with a higher risk of developing type 2 diabetes. However, don't clear it all out of your bathroom cabinet just yet. The association only existed for people who were using mouthwash at least twice a day, and the study only included people who had a number of pre-existing factors that put them at higher risk for developing the conditions.

The study, published on September 20 in Nitric Oxide, used data from 945 overweight or obese people who joined the San Juan Overweight Adults Longitudinal Study, based in Puerto Rico.

"Participants who used mouthwash at least twice daily had 55 percent significantly increased risk of developing pre-diabetes or diabetes over a 3-year follow-up compared to less frequent users, and 49 percent higher risk compared to non-users of mouthwash," the authors wrote. Specifically, 30 percent of the group that used mouthwash at least twice a day developed one of the two conditions; that number was 10 percentage points less in the group of people who used mouthwash less frequently.

"There is no reason to believe it is restricted to overweight and obese people," epidemiologist Kaumudi Joshipura told Newsweek, though being overweight is itself a risk factor for developing diabetes and prediabetes. "We can't know for sure, but at the same time, if I had to guess I think it may be generalizable to other populations."

However, the study doesn't show conclusively that mouthwash is causing diabetes. It only shows an association between significant usage and the disease.

The authors did control for many other risk factors associated with diabetes and prediabetes, including exercise and waist circumference, although they do not mention if they controlled for weight gain over the three-year follow-up. And a majority of the participants —nearly 65 percent—showed signs of moderate or severe gum disease to begin with. That proportion was consistent even among the group that was using mouthwash twice a day and is far higher than the national average. According to the CDC's most recent report on periodontal issues, about a third of U.S. adults have moderate or severe dental diseases.

Diabetes is actually one of the risk factors for bad oral health, according to the National Institute of Dental and Craniofacial Research.

The authors speculated that the association between increased rates of diabetes among those who used mouthwash so much might be because the mouthwash was killing bacteria that process nitric oxide. At least one study linked the bacterial composition in the mouth with diabetes; those bacteria may also have been linked with obesity.

Killing bacteria is a mouthwash's basic job; bacteria are also responsible for bad breath. But if you'd like to keep your breath minty fresh, you're probably better off establishing a healthy oral hygiene routine that involves regular flossing and brushing than working up such an extreme mouthwash habit. If you're not sure you're brushing properly, the American Dental Association has some information for you to double-check. The ADA also has an opinion on mouthwash. "While not a replacement for daily brushing and flossing, use of mouthwash (also called mouthrinse) may be a helpful addition to the daily oral hygiene routine for some people," the American Dental Association states on its website.

Mouthwash doesn't necessarily help fight against periodontal disease, Joshipura said—most of the ones you'd find on pharmacy shelves are indicated for preventing cavities and bad breath. "If you don't have a real reason to use it, I wouldn't just use it," she added.

However, she noted that this was just the first study to show a link like this. It couldn't hurt to still follow recommendations that had a bit more evidence behind them. If you're really serious about preventing diabetes, toning down or eliminating the use of mouthwash probably won't be enough. Lifestyle changes like exercising more and eating healthier foods are among the preventive measures recommended by the National Institute of Diabetes and Digestive and Kidney Diseases.

This article has been updated to include quotes from the study's author.