The meta-analysis used data from 13 prior studies that included a total of 1,616 subjects, spanning a wide range of subjects, intake method, and dose. About half of all women develop at least one urinary tract infection in their lifetimes.
Much to the scientists' surprise, cranberry juice prevailed over concentrates in pill form. This may not reflect health benefits of the cranberry juice itself, but rather drinking more fluids in general. Since drinking water helps flush bacteria from the system, subjects who drank juice could have been better hydrated than those taking pills.
University of Pennsylvania urologist Ariana Smith agrees that cranberry juice can be helpful, but says it certainly doesn't work for everyone. For those who can't visit a doctor for whatever reason, say, a lack of insurance, drinking cranberry juice is a convenient alternative, she said.
So how much should you drink to reap the benefits?
Chien-Chang Lee, an emergency medicine doctor who worked on the study, couldn't pinpoint an ideal dose, but said at least one eight-ounce glass twice per day would be a reasonable start.
Results should be interpreted with great caution due to discrepancies in the studies under review. Lee also warns that most of the studies involved a high-risk population, so it is not yet known whether cranberry would protect healthy individuals.
— Meeri Kim