A cup of green tea per day may help keep gum disease at bay, a new study suggests.

Researchers found that among middle-aged Japanese, the odds of having gum disease declined as the men's intake of green tea rose.

For each daily cup they drank, the risk of having signs of gum disease — including receding, easily bleeding gums — inched downward, the researchers report in the Journal of Periodontology.

The findings do not mean, however, that green tea is a substitute for seeing the dentist. The relationship between green tea and lower odds of gum disease was fairly weak, Dr. Yoshihiro Shimazaki, one of the researchers on the study, told Reuters Health.

Good overall oral care, Shimazaki said, is what's most important.

For the study, Shimazaki and his colleagues at Kyushu University in Fukuoka, Japan, examined 940 men between the ages of 49 and 59 for signs of gum disease. The men also completed a questionnaire on smoking and drinking habits, tooth-brushing habits and green tea intake.

In general, the study found, the odds of gum disease declined as green tea intake climbed, even with the other lifestyle factors considered. The researchers did, however, lack information on the men's overall diet, and past studies have suggested that certain foods and nutrients — like whole grains, fiber and vitamin C — may protect against gum disease.

If green tea itself does combat gum disease, it may be because of its concentration of antioxidant compounds called polyphenols, according to Shimazaki.

Gum disease arises from bacterial infection, and lab research suggests that green tea polyphenols can inhibit those germs and the damage they cause.