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Evidence-Based Complementary and Alternative Medicine
Volume 7 (2010), Issue 2, Pages 227-232
Original Article

Anti-microbial Activity of Urine after Ingestion of Cranberry: A Pilot Study

1Department of Medicine, Division of Infectious Disease, Irvine School of Medicine, University of California, CA, USA
2Department of Family Medicine & Geriatrics, Irvine School of Medicine, University of California, CA, USA
3MSEd, 200 S. Manchester #512, Orange, CA 92868, USA

Received 14 March 2007; Accepted 18 December 2007

Copyright © 2010 Yee Lean Lee et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We explore the anti-microbial activity of urine specimens after the ingestion of a commercial cranberry preparation. Twenty subjects without urinary infection, off antibiotics and all supplements or vitamins were recruited. The study was conducted in two phases: in phase 1, subjects collected the first morning urine prior to ingesting 900 mg of cranberry and then at 2, 4 and 6 h. In phase 2, subjects collected urine on 2 consecutive days: on Day 1 no cranberry was ingested (control specimens), on Day 2, cranberry was ingested. The pH of all urine specimens were adjusted to the same pH as that of the first morning urine specimen. Aliquots of each specimen were independently inoculated with Escherichia coli, Klebsiella pneumoniae or Candida albicans. After incubation, colony forming units/ml (CFU ml−1) in the control specimen was compared with CFU ml−1 in specimens collected 2, 4 and 6 h later. Specimens showing ≥50% reduction in CFU ml−1 were considered as having ‘activity’ against the strains tested. In phase 1, 7/20 (35%) subjects had anti-microbial activity against E. coli, 13/20 (65%) against K. pneumoniae and 9/20 (45%) against C. albicans in specimens collected 2–6 h after ingestion of cranberry. In phase 2, 6/9 (67%) of the subjects had activity against K. pneumoniae. This pilot study demonstrates weak anti-microbial activity in urine specimens after ingestion of a single dose of commercial cranberry. Anti-microbial activity was noted only against K. pneumoniae 2–6 h after ingestion of the cranberry preparation.