Lee Swanson Research Update

Study Supports Cranberry Dose Levels for Urinary Health

June 2010

The effectiveness of cranberry proanthocyanidins (PACs) is dependent on the dose, with higher doses significantly more successful in maintaining urinary health, according to a new study.

Indeed, a lower dose of 18 mg of cranberry PACs was less effective, according to the results of a randomized, double-blind-versus-placebo study based in Japan, Hungary, Spain and France.

On the other hand, a higher dose of 72 mg was even more efficient at protecting against bacterial adhesion in the urinary tract, according to findings published in the open-access journal BMC Infectious Diseases.

PACS are not exclusive to cranberries, but can be found in a range of foods, including green tea, grapes, apples and chocolate. However, the main type of PACs in cranberry—called A-type PACs—are different from those in other sources, called B-type PACS. Only cranberry PACS may prevent bacterial adhesion.

Led by Amy Howell from the Marucci Center for Blueberry and Cranberry Research and Extension at Rutgers University, the researchers note that, while the urinary tract benefits of cranberry are well documented, it was not known how cranberry PACs may affect the persistence in urine samples over a longer time period. They also sought to determine the “most effective dose per day and to determine if the urinary anti-adhesion effect following cranberry is detected within volunteers of different origins.”

Howell and her co-workers recruited 32 volunteers from the four countries and randomly assigned them to receive 0, 36 or 72 mg of PACs per day in Japan and Hungary and 0, 18 and 36 mg per day in France and Spain. Participants crossed over to all of the interventions with a one-week washout between stages.

Results showed a dose-dependent effect. After six hours the 18 mg dose displayed an anti-adhesion activity of 50%, compared with an average 90% for the 36 mg dose and 100% for the 72 mg dose, the researchers said.

After 24 hours, no anti-adhesion activity was displayed for the lower dose, while the 36 and 72 mg doses had anti-adhesion activities of 12.5% and 50%, respectively.

“These results highlighted for the first time that to achieve a bacterial anti-adhesion effect in urine, 36 mg of cranberry PAC equivalents per day is effective, but 72 mg may offer [day and night] protection,” wrote Howell and her co-workers.

The kinetic data revealed that while there was good activity for both 36 mg and 72 mg after six hours, this decreased after 24 hours, “suggesting that it may be beneficial to consume cranberry in two split doses of 36 mg in the morning and evening,” they added. “Further human trials are needed to correlate the level of ex vivo anti-adhesion activity with prevention of clinical UTI,” stated the researchers.

BMC Infections Diseases Published online ahead of print.

 

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