Does Cranberry Juice Help Repress or Reduce Urinary Tract Infections? A study in skeptical juice drinking.

This post was chosen as an Editor's Selection for ResearchBlogging.orgAfter 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.

ResearchBlogging.orgThe 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 The study seems old, using somewhat out of date methods, and there is not enough detail to evaluate it.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

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.


More like this

Are there even studies on skepticism in the medical community?

A few years back, I served on an NIH special study section (through NCCAM) geared to evaluate the effectiveness of cranberries on human disease. It was a learning experience for me in how completely fucked up a study section can be. Regardless, it was clear NIH was interested in sorting this issue out. Based on that experience, cranberries appear to be useful in treating/preventing cancers, bacterial- viral- and fungal-associated diseases, and a variety of other ailments.

Based on the little I've followed the cranberry field, I think the support for treating/preventing bacterial UTIs is pretty good. Beyond that, not so much.

"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%)."

(hehehe - 20$)

Aww ... such a pity that my statistician buddy's moved to Wales. I'd love to show him that statement just to see him turn red as a cranberry and start screaming.

As for the abstract of that last paper, I interpret that as saying "the cranberry treatment doesn't really work and is not worthwhile" - but that may simply be a bias from me reading hundreds of medical articles in the days when I was a research chemist. I'll admit that medical pubs have improved over the past few decades, but the sort of nonsense from articles in, say, the early 1960s are still common.

At any rate, the pro-cranberry claims appear to involve e. coli - since that is one of the best studied and abused bugs in the history of biology, experiments in a Petri dish may be cheaper and far more effective than these numerous cranberry drinking sessions.

By MadScientist (not verified) on 13 Aug 2010 #permalink

@Greg Laden - are you implying that those Petri dishes which do not drink cranberry juice might possibly be prone to bladder infections?

Anyways. It always surprises me a little bit when skeptics dismiss old-fashioned "home remedies" like this solely because they are so simple. Science doesn't have to be complicated -- Occam's razor actually indicates the opposite in most cases -- but for some reason there's a certain level of simplicity that just seems to create disbelief. I wonder whether there's a measurable level at which something becomes too simple to easily believe? Perhaps it's just the sheer volume of woo out there these days that makes the easy things seem just too easy.

As a woman with constant UTI symptoms & problems, I can tell you that cranberry doesn't mean squat if you're super susceptible. Those lucky women I know, who rarely get symptoms, get by with cranberry tablets. It seems to simply come down to "girls have too much plumbing."

#8, there is more going on than simply being 'super susceptible' when not responding to cranberry juice preventives, or having 'too much plumbing'.

You have a chronic inflammation issue (tissue overgrowth and loss of tight junctions), with repeating UTI presenting as secondary cause of pathology. If you also have frequent vaginal infections or unusual menstrual cycle symptoms, it would be worth investigating further for potential systemic cause of cyclic or hyperactive inflammatory response.

You may also have drug resistant strains complicating treatment.

Actually Sue for UTI it's that girls have too little plumbing. The urethra is short and has more direct exposure to outside contamination compared to men.

#8, has your doctor(s) looked into the cause of the recurrance? My dad had a sort of kink in his urethra and they had to insert a tube for a while, if I understood correctly, so that he could fully void his bladder, else the bacteria had too much chance to breed. Chronic infections take away so much of your energy, I sympathize and really hope there's a permanent cure for your problem.

By Samantha Vimes (not verified) on 14 Aug 2010 #permalink

Thanks for this post Greg.

By Katherine (not verified) on 15 Aug 2010 #permalink

Thanks, this was really neat. I am very susceptible to UTIs (which for myself, quickly become kidney infections...). Mine infections are associated with intercourse, and cranberry pills do help take the number of times I suffer one down. Mine are also usually hard to treat, so avoidance is very important...
Many people who I know that seem to not know their "triggers" often tell me cranberry does nothing for them(or in inflammatory cases, makes it burn worse) but I have had success in it. Nice to know I wasn't imagining that.

My daughter has spina bifida and has to be in-and-out catheterized four times a day. She is at huge risk for bladder infections because of this. At one time she was on prophylactic antibiotics, but her urologist has switched her to cranberry pill supplements (she takes four each day, two am and two pm). She has actually had fewer UTIs on the cranberry supplement than she had on the antibiotic, and has no apparent side effects.

We were told by her urologist (and this is consistent with what I have seen in the literature) that it's difficult to drink enough cranberry *juice* to make a difference, but that the concentrated form in the pills (and she takes more than are recommended on the bottle) gives her a high enough dose of whatever that ingredient is to be protective. So for anyone who is prone to UTIs, cranberry juice may not be effective but the pill form (actually, they're little gels) might.

Is there any evidence that drinking beer reduces the rate of UTIs in men? 'Cuz that's one finding I would readily accept without skepticism.

I think for a lot of women, cranberry juice is more a way of getting rid of a feeling of heaviness around the kidneys (because it makes you urinate more) than of actually fighting UTI. But then again, I've never had a UTI....

Maureen 17: do I understand correctly that you think people are mistaking a UTI for a feeling of heaviness around the kidneys? Only someone who's never had a UTI could make that mistake, believe me! They are unmistakeably miserable. Indeed, one of the miserable things about being prone to them is that one learns to recognise very early that a UTI is on the way, and so knows that it is likely to get a lot worse before it gets better. (Fending it off at that stage with water and cranberry juice may possibly shorten the eventual duration, but for me at least, doesn't often stop it arriving in full force.)

This is all interesting. When my bladder wants to go crazy, it does, no matter what. This has been true since I was a toddler; one of my earliest memories is of painful urination. (No intercourse then, I can assure you!) After I was diagnosed with fibromyalgia, my doctor suggested that it's probably interstitial cystitis (chronic bladder wall inflammation) rather than recurring bladder infections.

Erica, you said something interesting: "Many people who I know that seem to not know their 'triggers' often tell me cranberry does nothing for them (or in inflammatory cases, makes it burn worse)" -- those women might want to get a urine culture to make sure it is actually a UTI and not interstitial cystitis; A.D.A.M. says such patients should avoid cranberry juice. Apparently there's a prescription medication (Elmiron) that's approved for treatment; I've never used it, so I can't endorse it. I just learned my triggers and do my best to avoid too much coffee, too much booze, and not enough water. Best of luck to all of us, and thanks for the summary, Greg!

Thanks for covering this - I think there's a tendency in the skeptical community to lump every kind of plant based medicinal treatment into the same category of homeopathy, which seems to me obviously silly, given how much of our our pharmacopeia is plant-based.


By Sharon Astyk (not verified) on 20 Aug 2010 #permalink

@ #8
I think it depends, Sue. As a child with "constant UTI symptoms & problems" my pediatric nephrologist recommended my mother give me cranberry juice for recurrent infections. Although I can't really perform a paired t-test on infection frequency, the cranberry juice intake (and believe me, once the Dr told my worried mother to give me cranberry juice, I drank little else) did seem to really help infection frequency.

This is helpful, thank you very much.

Jepson & Craig: In this review we assess the effectiveness of cranberry and blueberry products in preventing symptomatic urinary tract infections (UTIs)... No relevant trials of blueberry products were identified.

Can someone more versed in the esoterica of scientific review articles please explain to me why, in the absence of usable data, blueberries were even mentioned here?

By Pierce R. Butler (not verified) on 25 Aug 2010 #permalink

Because blueberries, at least taste good so it would be good if they were good for something else.

So when do we get a review study on BLT sandwiches and chocolate cake as AIDS therapy?

By Pierce R. Butler (not verified) on 25 Aug 2010 #permalink

Pierce R. Butler asked: "Can someone more versed in the esoterica of scientific review articles please explain to me why, in the absence of usable data, blueberries were even mentioned here?"

They're mentioned because it indicates that blueberries were part of the research question/search strategy but the search turned up no clinical data (that met their inclusion criteria).

I've done this sort of writing before. Typically you'll have a set of research questions to answer (eg. What is the effectiveness of cranberries for UTI? What is the effectiveness of blueberries for UTI?) There will also be a search strategy that will indicate what kind of evidence is being included (eg. only randomized clinical trials? other study designs? etc.) and other inclusion criteria (for example it may be restricted to specific age groups, genders, outcomes or comparisons between treatments). It's done in a systematic way.

Without having read the full text, in this case it was probably something like:

Q: What is the clinical effectiveness of blueberries for reducing urinary tract infections?
A: No relevant studies of blueberries for UTI were identified.

As to why include them in the study design at all, they probably contain similar compounds to cranberries, or some other reason to be interested in this question. Plus they taste good.

If one wants to try cranberry juice as a preventive or a remedy, there's no way for the consumer to know that they're getting enough cranberry juice, given what's on the grocery shelves. None of the various juice blends on the grocery shelves indicate actual cranberry juice content. There is no product that's 100% cranberry juice (probably would be much too sour to drink.) I inquired Ocean Spray on the cranberry content of their cranberry drink labeled as "100% juice." Their response: "We are unable to provide the formula breakdown by individual fruit juices, as this is considered proprietary information." Unbelievable. They refuse to tell consumers what we're buying & ingesting. Bottom line is that the recommendation to drink cranberry juice is largely useless a minimum effective dose can be quantified and consumers can find products that actually meet that standard. Otherwise, we're just greatly increasing our sugar intake for nothing.

d.n., as annoying as the cranberry industry is, and it is, what you are saying is incorrect. No study has looked at dosage. None. Not one. Nada. Therefore, it is not very scientific to say that we can't reach the minimum dose. We have no clue what the min. dose is. I'ts been a while, but IIRC studies used something like 100 ml of cranberry juice (which itself is not quantified but I take that to mean juice of the berry without dilution) per day and every study showed a positive effect even if the effect was not statistically sig. owing to poor study design. Who knows, maybe 10 ml a day is plenty! If so, drinking "pure" juice labeled as cranberry (which as you say is unknown quantity) would probably be enough if you had a couple glasses a day of it.

I'm sure we've addressed this in the comments, but maybe not.

The bottom line is:

1) We don't know

2) There are positive indicators and, most interesting (to me):

3) Perfectly intelligent people are willing to say things definitively as long as they are negative, even though...

1) We really, really don't know.

For at least forty years, I've been aware of cranberries being used for these infections . From time to time my wife has gotten UTIs, and less frequently, so do I. We treat them with big glassfuls of cranberry juice. Exact "dosage" has never been an issue. A couple of years ago, an MD told me that's what he would have recommended.

By John Swindle (not verified) on 24 Aug 2011 #permalink

I guess no-one's ever studied what blueberries as an antibacterial? Too bad! But they could be included as a control: cranberry juice vs. random juice.

Cranberries are very sour so most of the juice in "cranberry juice" is apple.

People have studied other berries, including blueberries. Unfortunately, the good tasting berries don't seem to do anything but stain your carpet.

Actual cranberry juice that does not contain apple juice is sometimes available; often it's the fairly expensive and oddly-marketed organic stuff. I like it because I find many mixed drinks (cocktails / highballs) unacceptably sweet, and the taste of cheap distilled alcohol ("well-grade" whiskey, vodka, gin, tequilla, etc.) is rather nasty. No-sugar, no-apple, pure cranberry juice makes a fine mixer that can cover the taste of cheap booze very effectively, especially when mixed 1:1 with club soda (NOT tonic water). Turns out Southern Comfort actually has a pleasant flavour of its own, under that cloying sweetness.

It's really hard to find, though, and when it is available it's generally quite expensive. It's pretty damn sour, but it is drinkable. Especially if one has the opposite of a sweet tooth.

In other words: it does too taste good!

45mL vodka
90mL club soda
90mL pure cranberry juice, no sugar added
2-3 ice cubes
Serve in a highball glass (8 ounce)
- tastes extremely dry, the opposite of a sweet drink.

Martian Stark
45mL vodka
90mL club soda
90mL pure cranberry juice, no sugar added
50g dry ice (frozen CO2)
- tastes extremely dry, but with a hard-edged chemical sourness from the oversaturation by carbonic acid and the unavoidable inhalation of CO2 at much higher than typical atmospheric partial pressure.
Recommended: place the dry ice inside a "tea ball" before dropping into the drink, to help avoid accidental ingestion of any solid dry ice chips.

By TheBrummell (not verified) on 25 Aug 2011 #permalink

Now can you tell my stupid doctor this. Having just quoted the New England Journal of Medicine at me I can't find anything relating to Cranberry Juice in that Journal since 1998. I am wondering if it was a poor translation in New Scientist. But I guess that is Australian medicine.

By Lizz Higgins (not verified) on 25 Aug 2013 #permalink

I had a UTI for over a week and could not kick it with my ordinary cranberry-pill regime. I bought Lady Somas Cranberry pills , and I kicked my UTI within a couple of hours.

That may have worked for you or it could have been a coincidence. There is no evidence that cranberry juice or concentrate would be sufficient to actually wipe out an infection. As discussed in this post, it might be true that cranberry juice (of an unknown quantity) regularly consumed would help a person from getting an infection. Basically, if you like juice and cranberry juice is on your list of favored juices, there is no harm in drinking it regularly (as opposed to some other juice) and there may be a benefit. The key point here is this: Despite hyperskepticism saying that the evidence says that cranberry juice simply has no effect, the meta-studies seem to show that it MIGHT have an effect. But extending this to using it to fight an existing infection is actually probably a bit dangerous. But, I'm sure that if you have more severe symptoms of an infection you'll see a doctor.

I read that the key mechanism for cranberry preventing recurring UTIs is the relatively high levels of the common sugar mannose in cranberries.

The bacteria that are involved in UTIs need to bind to the bladder walls in order to cause infection, and do so by binding to the mannose sugars that are present on the surfaces of the cell membranes of the bladder cells.

By drinking cranberry juice, one can raise the level of mannose excreted in the urine to a sufficient level to tie up most of the binding sites in bacterial receptors, rendering them unable to attach to the bladder walls. They then get peed out the bladder when you urinate and flushed away harmlessly.

This reveals why store-bought "cranberry" juice (often a mixture of diluted concentrates, and sometimes "cranberry flavored") -- all of which contain too much sucrose (not mannose) is not as effective -- and why people search for "real"/pure cranberry juice.

But (assuming the above is accurate), a little thought reveals that you can "cut to the chase": Drink an aqueous mixture of mannose sugar to do the job.

My wife drinks a powdered form of mannose + dried cranberry solids mixed with water. I can say after 7 years that when followed it is 100% effective in prevention (but it's not curative!).

Similarly, skipping a daily does is much like skipping The Pill: One morning you may start experiencing the beginning symptoms of an unwanted condition...

Scientific? Well, for this one "test subject", 7 years of use (and occasional "I forgot!") have established a VERY repeatable set of results. YMMV. Google for mannose/cranberry products...

By Brainstorms (not verified) on 22 Sep 2014 #permalink

I have been struggling with a UTI for many years, this is very helpful information...thank you!

Ive tried many products recommended by my naturopath. But my bladder infections were becoming unbearable. Antibiotics are what got me into this mess in the first place!

I took the Lady Soma Cranberry Pills full dose each day for about a week, I felt less inflammation in my gut and food felt easier to digest. It’s been a couple weeks now, and I’m feeling overall less fatigued and having fewer headaches. Meanwhile, I haven’t changed anything else in my daily routine.