After I reported this recent and interesting research paper about urinary tract inflictions, a number of conversations broke out on that post, on my facebook page, and via email, and some of these conversations raised the question of cranberry juice and whether the idea that it prevents, reduces, or shortens the duration of UTIs is real or woo.
Added: After further discussion elsewhere, I would like to clarify what is being asked here: Imagine you are a person who drinks apple juice and cranberry juice as your main hydrating substance. Also, you are are a person who is concerned with UTIs. One day, you ask yourself: “I want to switch to drinking only one kind of juice, apple or cranberry. Should I make it cranberry, with the idea that it could prevent UTIs, to some degree, for me? No biggie if it does not, but is there a reasonable chance that it will?” This is NOT a post about whether or not cranberry juice in any concentration or form can treat a UTI. Obviously.
So, I decided to use Gooogle Scholar (which is a version of Google that you should probably use more often than you currently do) to find out what the peer reviewed literature says. First I entered a few appropriate search terms (bladder infection UTI cranberry, for example) and looked at the first few references provided, then I narrowed the search for the most recent five years. That narrowing gave me a recent review article (which is what I was hoping for).
I came to a conclusion about cranberry juice after just few minutes of looking at abstracts and a couple of full text papers, and then spent considerably more time summarizing my results for you. Here is what I found:
A 1998 letter to the editors of the New England Journal of Medicine (Howell et al. 1998) states that…
The consumption of cranberry juice has been recommended for the prevention of urinary tract infections, and a 1994 clinical study provides scientific validation of this claim. The effect is due not to the highly acidic nature of cranberries but to specific compounds in cranberries that inhibit the adherence of Escherichia coli to uroepithelial cells.
The letter then goes on to indicate that tannins in the cranberry juice prevent UTI causing E. coli to adher to the urinary tract. The study seems old, using somewhat out of date methods, and there is not enough detail to evaluate it. On the other hand, the letter is meant to summarize a series of five other studies published as early as 1981, for which it provides abstracts, and they seem supportive of the idea of cranberry juice being effective.
In one study (Strothers 2002), 150 sexually active women aged 21 through 72 were given placebo juice and placebo tablets or placebo juice and cranberry tablets or cranberry juice and placebo tablets. “Both cranberry juice and cranberry tablets statistically significantly decreased the number of patients experiencing at least 1 symptomatic UTI/year (to 20$ and 18% respectively) compared with placebo (to 32%).” That seems to add weight to the cranberry juice idea.
A different study (Kontiokari et al, 2001) sought to evaluate the effects of recurrences of UTIs of consuming cranberry-lignonberry juice and Lactobacillus GG drink. One hundred and fifty women with UTI’s were allocated to three treatment groups, one for each juice and a control group.
The cranberry juice drinkers had 50 ml of cranberry-lingonberry concenrtrate every day for six months. The lactobacillus users had 100 ml of that liquid for five days per week over one year. The control group got nothing. “At six months, eight (16%) women in the cranberry group, 19 (39%) in the lactobacillus group, and 18 (36%) in the control group had had at least one recurrence.” Conclusion: Cranberry juice helps. Lactobacillus does not. The sample sizes are not overwhelming, but running the study over a years time seems to add strength to the assertion.
A much larger study was reported in 2005 (McMurdo et al. 2005) using a double-blind placebo controlled randomised methodology with 376 hospitalized patients. Daily doses of 300 ml of cranberry juice or a placebo were given at the onset of a UTI. The results:
a total of 21/376 (5.6%) participants developed a symptomatic UTI: 14/189 in the placebo group and 7/187 in the cranberry juice group. These between-group differences were not significant, relative risk (RR) 0.51 [95% CI 0.21-1.22, P=0.122). Although there were significantly fewer infections with Escherichia coli in the cranberry group (13 versus 4) RR 0.31 [95% CI 0.10-0.94, P=0.027], this should be interpreted with caution as it was a secondary outcome.
The authors concluded that cranberry juice ingestion can not be said to work, but the actual infection rate in the study was so low that the study had insufficient power to really test the case. Note also that this is a short term infection-case study, rather than a long term infection rate study. And, these were people of a very narrowly defined demographic.
Also in 2005, a study by Zhang et al. a double-blind trial was carried out in China with a sample size of 189 adults (mean age 49 yrs). These individuals had H. pylori infections. It was concluded that “Regular consumption of cranberry juice can suppress H. pylori infection in endemically afflicted populations.”
A 2006 study by Martino et al using double blind placebo controlled crossover approach, on 10 men and 10.
… each volunteer received … a single dose of 750 ml of a total drink composed of: (1) 250 ml of the placebo and 500 ml of mineral water, or (2) 750 ml of the placebo, or (3) 250 ml of the cranberry juice and 500 ml of mineral water, or (4) 750 ml of the cranberry juice. Each volunteer took the four regimens successively in a randomly order, with a washout period of at least 6 days between every change in regimen. The first urine of the morning following cranberry or placebo consumption was collected and used to support bacterial growth. Six uropathogenic Escherichia coli strains (all expressing type 1 pili; three positive for the gene marker for P-fimbriae papC and three negative for papC), previously isolated from patients with symptomatic urinary tract infections, were grown in urine samples and tested for their ability to adhere to the T24 bladder cell line in vitro. There were no significant differences in the pH or specific gravity between the urine samples collected after cranberry or placebo consumption. We observed a dose dependent significant decrease in bacterial adherence associated with cranberry consumption. Adherence inhibition was observed independently from the presence of genes encoding type P pili and antibiotic resistance phenotypes. Cranberry juice consumption provides significant anti-adherence activity against different E. coli uropathogenic strains in the urine compared with placebo.
This supports the earlier studies indicating that E. coli adherence to tissues is inhibited by sometning in the cranberry juice.
There are more studies, but I’ll finish the survey with tis one: A systematic review of the evidence for cranberries and blueberries in UTI prevention (Jepson and Craig 2007). Here’s the abstract:
In this review we assess the effectiveness of cranberry and blueberry products in preventing symptomatic urinary tract infections (UTIs). Selection criteria were randomised or quasi-randomised controlled trials of cranberry or blueberry juice/products for the prevention of symptomatic UTIs. A comprehensive search was undertaken in November 2006 whereupon two reviewers independently assessed and extracted data. Quality was assessed using Cochrane criteria. Relative risks (RR) were calculated where appropriate; otherwise a narrative synthesis was undertaken. No relevant trials of blueberry products were identified. Nine trials of cranberry products met the inclusion criteria. In four good quality randomised controlled trials (RCTs), cranberry products significantly reduced the incidence of symptomatic UTIs in 12 months (overall RR 0.65, 95% CI: 0.46-0.90) compared with placebo/control. Five trials were not included in the meta-analyses due to the lack of appropriate data. However, only one reported a significant result. Side effects were common, and losses to followup/withdrawals in several of the trials were high (> 40%). There is some evidence from four good quality RCTs that cranberry juice may decrease the number of symptomatic UTIs over a 12-month period, particularly in women with recurrent UTIs. It is uncertain whether it is effective in other susceptible groups.
I don’t have access to this article, so I can’t tell you if any of the studies it looked at are the ones I already mention above, but I’ll bet that is in fact the case for at least one or two.
I have two conclusions from this exercise: 1) The cranberry juice essentially works; and 2) There is a pattern of change in optimism about the effectiveness of this home remedy from more to less optimistic even as data piles up indicating mostly that it is effective. This, I suspect, is the result of increase skepticism in the medical community.
Howell, A. B., Vorsa, N., & Marderosian, A. D. (1998). Inhibition of the Adherence of P-Fimbriated Escherichia coli to Uroepithelial-Cell Surfaces by Proanthocyanidin Extracts from Cranberries. The New England journal of medicine, 339(19), 1408. doi: 10.1056/NEJM199811053391922.
Jepson, R., & Craig, J. (2007). A systematic review of the evidence for cranberries and blueberries in UTI prevention Molecular Nutrition & Food Research, 51 (6), 738-745 DOI: 10.1002/mnfr.200600275
Kontiokari, T. (2001). Randomised trial of cranberry-lingonberry juice and Lactobacillus GG drink for the prevention of urinary tract infections in. BMJ, 322(7302), 1571-1571. doi: 10.1136/bmj.322.7302.1571.
Martino, P., Agniel, K., David, C., Templer, J., Gaillard, L., Denys, P., et al. (2006). Reduction of Escherichia coli adherence to uroepithelial bladder cells after consumption of cranberry juice: a double-blind randomized placebo-controlled cross-over trial. World journal of urology, 24(1), 21-27. Retrieved from http://www.springerlink.com/content/yr5v556687821867/.
McMurdo, M. E., Bissett, L. Y., Price, R. J., Phillips, G., & Crombie, I. K. (2005). Does ingestion of cranberry juice reduce symptomatic urinary tract infections in older people in hospital? A double-blind, placebo-controlled trial. Age and ageing, 34(3), 256-61. doi: 10.1093/ageing/afi101.
Strothers, L. (2002). A randomized trial to evaluate effectiveness and cost effectiveness of naturalpathic cranberry products as prophylaxis against urinary tract infection in women. The Canadian Journal of Urology, 9(3), 1558-1562.
Zhang, L., Ma, J., Pan, K., Go, V. L., Chen, J., You, W., et al. (2005). Efficacy of cranberry juice on Helicobacter pylori infection: a double-blind, randomized placebo-controlled trial. Helicobacter, 10(2), 139-45. doi: 10.1111/j.1523-5378.2005.00301.x.