The Journal of Young Investigators: An Undergraduate, Peer-Reviewed Science Journal

07 June 2005 - Raisins could replace apples as the fruit to eat everyday to “keep the dentist away.” Researchers at the University of Illinois College of Dentistry found that raisins contain five compounds that reduce the number of cavity-causing bacteria in the mouth. The data were presented on June 7, 2005 at the annual meeting of the American Society for Microbiology in Atlanta.

The compounds found in raisins fall into the category of phytochemicals, a plant chemical that offers no nutritional value, but prevent infections. Phytochemicals are currently a popular material to research because of their cancer and disease fighting properties, according to the American Cancer Society.

Christine Wu and her team found five compounds in Thompson seedless grapes, betulin, betulinic acid, oleanolic acid, oleanolic aldehyde, and 5-(hydroxymethyl)-2-furfural, slowed the growth of Streptococcus mutans and Porphyromonas gingivalis. S. mutans is known to cause cavities, while P. gingivalis causes periodontal disease, or gingivitis.

One of the chemicals - oleanolic acid – also prevents S. mutans from attaching to the enamel surface of the tooth. Tooth decay occurs when S. mutans to the surface, creating a sticky layer for more bacteria to adhere to, resulting in a matrix of bacteria on the tooth. After eating sugary foods, the bacteria ferment the sugar and release acids that erode the enamel.

According to Wu, the findings 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," says Wu [present-tense quotes]. "But our study suggests the contrary. Phytochemicals in raisins may benefit oral health by fighting bacteria that cause cavities and gum disease."

Douglas Pick, a dentist in Chicago, found Wu’s results intuitive.

“Many people believe fruit can lead to tooth decay because of its high sugar content and sweet taste," says Pick. "Raisins contain fructose and glucose, not sucrose. The difference is sucrose is a complex sugar, causing tooth decay when it gets broken down in the mouth.”

Wu's collaborator Shahrbanoo Fadavi supports the theory that sugar, not sticky foods, causes the bacterial matrix and tooth decay, with an earlier unpublished study. Fadavi, a pediatric dentist at UIC, found that adding raisins alone to bran cereal did not increase the acidity of dental plaque. Raisin bran cereal with added sugar, however, did raise acidity levels.

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