"Our laboratory analyses showed that phytochemicals in this popular snack food suppress the growth of several species of oral bacteria associated with caries and gum disease," said Christine D. Wu, Professor and Associate Dean for Research at the University of Illinois at Chicago College of Dentistry and lead author of the study.
Routine chemical analyses identified five compounds in Thompson seedless raisins: oleanolic acid, oleanolic aldehyde, betulin, betulinic acid, and 5-(hydroxymethyl)-2-furfural. All of these are known phytochemicals -- antioxidants found in plants.
Oleanolic acid inhibited the growth of two species of oral bacteria: Streptococcus mutans, which causes cavities, and Porphyromonas gingivalis, which causes periodontal disease.
The compound was effective against the bacteria at concentrations ranging from about 4 to 1,000 g/ml. At a concentration of 31 g/ml, oleanolic acid also blocked S. mutans adherence to surfaces. Adherence is crucial for the bacteria to form dental plaque, the sticky biofilm consisting of oral bacteria that accumulates on teeth. After a sugary meal, these bacteria release acids that erode the tooth enamel.
Wu said that the data counter a longstanding public perception that raisins promote cavities.
"Raisins are perceived as sweet and sticky, and any food that contains sugar and is sticky is assumed to cause cavities," Wu said. "But our study suggests the contrary. Phytochemicals in raisins may benefit oral health by fighting bacteria that cause cavities and gum disease."
In an earlier unpublished study, Wu's collaborator Dr. Shahrbanoo Fadavi (Pediatric Dentistry, UIC College of Dentistry) found that adding raisins to bran cereal did not increase the acidity o
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Contact: Jim Sliwa
jsliwa@asmusa.org
202-942-9297
American Society for Microbiology
8-Jun-2005