A 2008 New York University study showed that daily flossing reduced the amount of gum-disease-causing bacteria in the mouth. This bacteria is thought to enter the bloodstream and trigger inflammation in the arteries, a major risk factor for heart disease. Other research has shown that those who have high amounts of bacteria in their mouth are more likely to have thickening in their arteries, another sign of heart disease. "I really do think people should floss twice a day to get the biggest life expectancy benefits," says Perls.