European settlers first put cranberries on the Thanksgiving table because the local fruit lasted through winter and enhanced the flavor of gamy meat. The settlers had picked up on the berry's culinary potential from Native Americans, who survived cold winters by filling up on pemmican, a cake of cranberries, nuts and dried venison or bear meat.
Both groups also prescribed cranberries for fevers, gastrointestinal problems and dropsy -- a term used to describe any swelling or inflammation. Turns out, they were onto something. In the last few decades, scientists have begun to confirm and explain the cranberry's ability to fight infections of the urinary tract and gut and its potential to fight gum disease, heart disease and cancer.
"For over a hundred years, women have known that cranberry juice can prevent urinary tract infections," says Amy Howell, associate research scientist at the U.S. Department of Agriculture-supported Marucci Center for Blueberry and Cranberry Research at Rutgers University in Camden, N.J. "They thought it was due to acidity, but that's actually not the case."
Cranberry's antibacterial properties are due to a class of chemical compounds called proanthocyanidins. Ten years ago, Howell's research group isolated the compounds and demonstrated how they work: Proanthocyanidins bind to harmful bacteria such as E. coli, forming a "Teflon-like" coating around them. The coating prevents the bacteria from sticking to gastrointestinal and urinary tract walls, impeding infections.
The nonstick properties of proanthocyanidins may explain the results of several clinical trials that showed that cranberry juice can reduce the frequency of urinary tract infections.
For example, a study published in the British Medical Journal in 2001 showed that women who drank a couple of ounces of cranberry juice daily for six months had a 20% lower risk of urinary tract infections, compared with women in a control group. A study published in the Canadian Journal of Urology in 2002 showed that just 20% of women who drank three glasses of cranberry juice daily for a year experienced urinary tract infection symptoms, compared with 32% of women who drank a placebo.
And last month, a study in the journal Urology found that two glasses of cranberry juice a day reduced the frequency of urinary tract infections by 41% among pregnant women.
