Daily swill of mouthwash could kill microbes that fight obesity and diabetes

The routine use of oral antibacterial products may do more harm than good, Harvard study concludes

MOUTHWASH may seem a beneficial, or at least harmless, addition to your daily tooth-brushing routine.

However, a new study suggests that swilling with anti-bacterial fluid could kill helpful microbes, which live in the mouth and protect against obesity and diabetes. While mouthwash is supposed to target the bacteria which cause plaque and bad breath, it is in fact indiscriminate, washing away beneficial strains.

Researchers at Harvard University found that people who used mouthwash twice a day were around 55 per cent more likely to develop diabetes or dangerous blood sugar spikes within three years. Although previous studies have also found that poor oral hygiene can lead to health problems elsewhere in the body, this is the first to show that seemingly positive practices can have unexpected negative consequences.

Kaumudi Joshipura, professor of epidemiology at Harvard School of Public Health, said: “Most of these antibacterial ingredients in mouthwash are not selective.

“In other words, they do not target specific oral bacteria. Instead, these ingredients can act on a broad range of bacteria.”

The study, published in the journal Nitric Oxide, looked at 1,206 overweight people aged between 40 and 65 who were deemed to be at risk of contracting diabetes.

Over the study period, around 17 per cent of people developed diabetes or pre-diabetes, but that rose to 20 per cent for those using mouthwash once a day, and 30 per cent for those who used it in the morning and evening.

Prof Joshipura said helpful bacteria in the mouth can protect against diabetes and obesity. They include microbes which assist the body produce the nitric oxide that regulates insulin levels and helps regulate the metabolism, balance energy and keep blood-sugar levels in check.

The first commercial mouthwash was developed in the late 19th century and named Listerine, after Joseph Lister, the British surgeon.

It was originally used as a surgical antiseptic, but by the 1920s it was sold as a cure for bad breath as well as a floor cleaner and dandruff remedy.

Today, many mouthwashes contain powerful bacteria-killing solutions including chlorhexidine, triclosan, cetylpyridinium chloride and peroxide.

The British Dental Association does not consider daily mouthwash use as necessary to oral healthcare and warns it does not ensure “food build-up and plaque are removed from your teeth”.

The Harvard research concluded: “The indiscriminate routine use of antibacterial mouthwash products may cause more harm than good.”