Yes, say researchers who study the gorgeous berry — although the National Center for Complementary and Alternative Medicine, which is sponsoring several clinical studies, says the data are “not conclusive.”

The queen of cranberry science, Amy Howell , an associate research scientist at Rutgers University in Chatsworth, N.J., said that overall, research suggests that eight to 10 ounces a day of cranberry juice cocktail drink, sweetened with either sugar or artificial sweetener, has been shown clinically to reduce urinary tract infections by 50 percent.

For years, people thought cranberry juice might combat urinary tract infections by making urine more acidic, thus making it harder for bacteria to grow.

Now, thanks to the work of Howell and others, it is known that a chemical in cranberries called proanthocyanidin blocks infections by coating E. coli, the major culprit, so that it cannot stick to cells in the bladder. “If you prevent the adhesion, the bacteria won’t multiply and cause infection,” Howell said.

That’s why it’s no big deal, she said, that there were “negative” findings in a recent study published in the American Journal of Health-System Pharmacy. That study showed that drinking cranberry juice was no more effective at preventing bacterial growth in urine than drinking water, said Sophie Chang , a clinical pharmacist at Cedars-Sinai Medical Center in Los Angeles and one of the authors.

Since the cranberry compounds don’t kill bacteria, there is less of a chance that the bacteria will become resistant, as they would with the antibiotics that are used to treat infections, said Howell.

A similar version of proanthocyanidin is found in blueberries, said Dr. Kalpana Gupta , assistant professor of medicine at Yale University School of Medicine.

Until recently, scientists thought that once you get a urinary infection, you need antibiotics. But data released last week suggest that cranberry juice may help treat, as well as prevent, urinary infections.