Raisins contain chemicals that suppress the growth and adherence of two species of oral bacteria associated with the development of cavities and periodontal disease, according to research presented Wednesday at the 105th General Meeting of the American Society for Microbiology in Atlanta.

“The results should help counter the long-standing public perception that raisins promote cavities,” said lead investigator Dr. Christine D. Wu from the University of Illinois at Chicago College of Dentistry.

In research funded by the California Raisin Marketing Board, Wu and colleagues isolated and analyzed the antibacterial activity of five known phytochemicals found in Thompson seedless raisins: oleanolic acid, oleanolic aldehyde, betulin, betulinic acid, and 5-(hydroxymethyl)-2-furfural.

Oleanolic acid, the most active compound, inhibited the growth of Streptococcus mutans, which causes cavities, and Porphyromonas gingivalis, which causes periodontal disease.

While oleanolic acid is not highly antimicrobial, Wu said, it prevents the adhesion of oral bacteria associated with dental plaque. Japanese researchers have already reported that oleanolic acid reduces in rats, she added.

“Raisins are not as bad for the teeth as people think,” she concluded. “Raisins do not contain high levels of sucrose. They contain mainly fructose and glucose, and these sugars do not support dental plaque formation.”