The research paper "Cranberries for preventing urinary tract infections" (DOI: 10.1002/14651858.CD001321.pub5) within the journal Cochrane Database of Systematic Reviews was authored by Ruth G. Jepson (University of Stirling, Department of Nursing and Midwifery, Stirling, Scotland, UK), G. Williams (The Children's Hospital at Westmead, Centre for Kidney Research, Westmead, NSW, Australia), and J. C. Craig (The Children's Hospital at Westmead, Cochrane Renal Group, Centre for Kidney Research, Westmead, NSW, Australia).
In 2008, the same research (only with fewer sources) showed that cranberries offered a small benefit in preventing recurring UTIs in women.
This team in 2012, researched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL in The Cochrane Library) and the Internet for sources on cranberry juice and urinary tract infections.
In 2012, these three researchers added 14 new studies to those reviewed in 2008. In all, a total of 4,473 people were analyzed.
The researchers conclude that current evidence does not support cranberry juice as a means of preventing UTIs.
According to the Medical Press article "Cranberry juice now unlikely to prevent cystitis", Dr. Ruth Jepson, one of the authors of the study, stated, "Now that we've updated our review with more studies, the results suggest that cranberry juice is even less effective at preventing UTIs than was shown in the last update"
Jepson added, "We can't see a particular need for more studies of the effect of cranberry juice, as the majority of existing studies indicate that the benefit is small at best, and the studies have high drop-out rates."
Further, she stated, "More studies of other cranberry products such as tablets and capsules may be justified, but only for women with recurrent UTIs, and only if these products contain the recommended amount of active ingredient."