People with a high risk of type 2 diabetes who use mouthwash twice a day are 55 per cent more likely to develop the condition within three years, a new study suggests.
While an association was observed between mouthwash and type 2 diabetes, the findings do not indicate that mouthwash causes type 2 diabetes, rather the effects of mouthwash need further examination.
Scientists at Harvard University were analysing links between over-the-counter mouthwash and its potential to predispose people to metabolic disorders because of the antibacterial ingredients mouthwash contains.
They evaluated 1,206 overweight people aged 40-65 who were deemed at high risk of developing type 2 diabetes.
Seventeen per cent of the study group developed prediabetes or type 2 diabetes, which rose to 20 per cent for those who used mouthwash once a day, an increase that was not deemed statistically significant. However, among twice daily users of mouthwash, the rate rose to 30 per cent, a statistically significant increase.
“The indiscriminate routine use of antibacterial mouthwash products may cause more harm than good, in light of recent studies, and further supported by findings from this study,” said the study authors.

“Mouthwash use may also have a detrimental impact on diabetes control and possible complications, as these share some common […] pathways with blood pressure and diabetes.”
Mouthwash is often thought of as a harmless addition to daily tooth brushing which helps to target plaque, but it is not listed by the British Dental Association as a necessary component of proper oral health care, and this study indicates mouthwash may wash away beneficial bacteria.
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.”
Prof Joshipura added that by washing away helpful bacteria in the mouth, the body is less able to protect against type 2 diabetes and obesity due to a loss of microbes which help the body produce nitric oxide, helping to regulate insulin levels.
There is also a possibility that those who use mouthwash more often may be more likely to have poorer health, and possibly poorer diets, compared to those who do not.
The way the study was run means that the researchers cannot say for certain whether mouthwash was definitely a contributing factor. It does, however, ask questions as to whether mouthwash is beneficial for people overall.
The findings were published in the journal Nitric Oxide.

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