The team from Tsurumi University in Yokohama, Japan found that 80 per cent of study volunteers had lower levels of hydrogen sulphide, a major cause of bad breath, after eating yoghurt for six weeks.
Levels of plaque and the gum disease gingivitis were also significantly lower among the yoghurt-eating group. The benefits are thought to come from the active bacteria in yoghurt,Lactobacillus bulgaricus and Streptococcus thermophilus.
The research was presented at the International Association for Dental Research meeting in the US earlier this month (abstract 920).
The 24 volunteers avoided yoghurts and similar foods, like cheese, for two weeks, after which the researchers measured bacteria levels and odour-causing compounds, including hydrogen sulphide, in saliva.
The volunteers then ate 90 grams of yoghurt a day for six weeks.
At the end of the study, researchers found hydrogen sulphide levels decreased in 80 per cent of participants.
One in four people suffer from bad breath regularly, while 19 in 20 are affected by gum disease at some point in their lives.