Journal: Caries Research, January 2006

Study: Oral biologists coated a synthetic tooth-enamel-like substance with cranberry juice and applied cavity-causing microbes, Streptococcus mutans—which metabolize sugars into acids that cause tooth decay—and found, after seven months of study, that cranberry juice acts like a non-stick coating that made it 80% effective in protecting teeth. Bacteria couldn't get a grip on tooth surfaces to construct a haven of plaque from which to attack teeth. The study is one of nine projects funded by the National Institutes of Health to investigate potential health effects of cranberries.

What it means: The cranberry's non-stick, protective properties might be why the berry has been shown to be effective against urinary tract infections and, in another study, helped inactivate intestinal viruses: bacteria and viruses can’t adhere to surfaces to infect them. But before you reach for the leftover cranberry sauce or go rinsing with cranberry juice, remember that sugar contributes to dental decay and more study needs to be done on what might make cranberry an effective agent in  keeping teeth strong.