Cranberry Juice

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Thinking of Using Cranberry?

This site is dedicated to showing the adverse effects of cranberry juice/powder/tablets on most urine infections, against the common myth that it is useful. Evidence-based research article.

The overwhelming cause of most urinary tract infections, E.coli, is an acid adaptive bacterium, and is capable of synthesising its nutritional requirements from the surrounding acids in its environment. Since cranberry creates acidic urine conditions, [See] (cranberry juice produces hippuric acid in the urine) when cranberry juice is drunk or cranberry tablets ingested, E.coli is provided a suitable environment in which to multiply.

Thus, cranberry makes urine infections worse. This is not a subtle point, nor one that is difficult to grasp. However, it does go directly against years of urban myth, so deeply ingrained in our society that it has become part of the public consciousness.

The trouble is that so many people in the NHS and aligned medical organisations like the Department of Health, have publically come out in favour of the use of cranberry for UTIs, that to put out contrary advice could upset some very powerful people. If your boss says one thing, or even, if he/she said it ten years ago, you are unlikely to contradict him/her. Not if you want that promotion. Not if you want part of that funding grant. Not if you want a good reference. Not if you want to be invited to that conference...

The clinical trials that have been done have been specifically designed to show up any positive effect from drinking cranberry, but nevertheless none appear to show results better than placebo, and it's difficult to find negative results because the sponsors - generally people producing cranberry, don't publish negative results. The only successes of cranberry have been as an ingredient in something else, but even there, for urine infections, the product would probably achieve greater success without the cranberry added.

But it's become part of our culture, and when that happens, a strange bias starts creeping in. People and organisations align themselves with widely held beliefs.

For an example of the strange bias that exists, looking at Clinical Answers (NHS) ( it is clear, even in this brief report, that despite the report showing that cranberry gives people more of a propensity for infection, the author obscures this fact. Near the top of the report, which people are far more likely to read, they say:

"There is some evidence from two good quality RCTs that cranberry juice may decrease the number of symptomatic UTIs over a 12 month period in women. If it is effective for other groups such as children and elderly men and women is not clear..."

That is interesting, because in a similar way almost every study/report in the cannon, that tries to show cranberry as being useful, similarly non-specifically references such positive studies by using the terms 'Studies suggest', or 'Modern research indicates', or 'Research has shown'.

Generally, this shows the influence of money influencing publically voiced opinion. The multi-billion dollar cranberry industry will fund any study that shows cranberry in a positive light, and where there is money to be made, there is truth to be obscured.

Further down, the report reverts to semi-technical language to explain: "The NICE guideline also refers to study of cranberry supplements for the reduction of urinary tract infections in individuals [n=21] with neurogenic bladders secondary to spinal cord injury. The authors, Linsenmeyer et al describe their methods: Individuals were recruited and randomly assigned to standardized 400-mg cranberry tablets or placebo 3 times a day for 4 weeks. After 4 weeks and an additional 1-week "washout period" participants were crossed over to the other group. Participants were seen weekly, during which a urine analysis was obtained. UTI was defined as significant bacterial or yeast colony counts in the urine and elevated WBC counts (WBC count > or = 10 per high power field) in centrifuged urine. Participants with symptomatic infections were treated with appropriate antibiotics for 7 days and restarted on the cranberry tablet/ placebo after a 7-day washout period. Urinary pH between the cranberry and placebo groups was compared weekly.”

Near the bottom of the report it says: "In terms of results, Linsenmeyer found: “There was no statistically significant treatment (favorable) effect for cranberry supplement beyond placebo when evaluating the 2 treatment groups for bacterial count, WBC count, or WBC and bacterial counts in combination."

Look at that again. Saying 'no statistically significant treatment (favourable) effect for cranberry supplement beyond placebo' is really saying there is a statistically significant unfavourable effect, in a way that won't be picked up by many people.

Right at the end of the report, (the least likely to be read) it says; "In the cranberry group 34.6% of participants failed (i.e., developed a UTI) versus 32.4% in the control group (p = .849)."


That is a statistically significant effect. Statistically, people taking cranberry were more 2.2% more likely to develop UTIs than people taking placebo (ie: nothing at all).

Now that's bad, but it is still about the least harmful trial result about cranberry ever found.

In real life, it becomes clear that cranberry exasperates most urine infections, not just 2.2% of them!

There is a small anti-adhesion effect from cranberry, but for the vast majority of bladder infection agents, the increased bacterial metabolic rate that results from the acidic urine that you get from drinking cranberry more than cancels out any anti-adhesion benefits from taking it.

On the other hand, it seems to be the case that for most gram negative bacteria, living in alkali conditions is like living in their own waste - not ideal conditions. In alkali urine they slow down their metabolic rate and it can take them twice as long to produce a cell division (to double). That's why taking potassium citrate, which makes the urine more alkaline [See] can help ease the situation.

Another reason not to take cranberry: it stops antibiotics from working. A lot of antibiotics work by damaging the cell walls of bacteria. Putting hippuric acid into your urine (by taking cranberry) causes the bacteria to develop thick skins to resist being damaged by the acid. It is then much harder for the antibiotic to do its job. What you find when somebody has been taing cranberry is that the infection returns to full strength within a week or two of finishing the course.

Major misunderstanding...

Since the healthy vagina is colonized by lactobacilli, which are beneficial microorganisms that maintain an acidic (low pH) environment in the vagina, it is often assumed that a similar low pH environment in the urine makes the bladder hostile to bacteria. This is simply not true. The bladder and the vagina are entirely different environments. In the vaginal area, Lactobacilli compete with other bacteria for resources, and as a by-product, they produce hydrogen peroxide which also creates a hostile environment for bacteria. The tissues of the vagina and the Lactobaccili cells are adapted for exactly this environment, and they are healthy when the pH is low - when the environment is acidic.

Urine, on the other hand is most unlikely to have Lactobacilli living in it, and bacteria that do colonise the bladder are usually pathogenic, and much tougher than Lactobaccilli. For the most part though, like Lactobaccilli, these pathogens do enjoy an acidic environment, and they don't thrive well in an alkali environment. And there's the point of it... the pH environment that provides a healthy living area for friendly bacteria in the vagina also provides a healthy environment for the distinctly unfriendly bacteria in the bladder.

It is also known that if the E.coli in your body originated from cattle fed on a high grain diet, they can be 1000 times more resistant to acid than other E.coli. These bacteria absolutely thrive in acids. They are tough little bugs that adapt to utilise the environment they are exposed to. They can even get through stomach acids intact.

Acid resistant bacteria populate the human gut when you eat meat or food contaminated with the acid-loving strains, [See] so the very first time you get an E.coli infection, the bacteria can already be acid resistant. (When you get an E.coli infection, the bacteria has invariably been at some point in a human bowel - it could be that person you just shook hands with... and not from you or your partner.)

And since Trimethoprim is often used to prevent and treat infections in chicken and cattle, the bacteria are also likely to have genetic Trimethoprim resistance 'built in'.

The cycle: E.coli and Klebsiella (and some other gram negative uropathogens) have 'burst cycle' population explosions that occur under optimum feeding conditions. It goes like this - you drink cranberry or something else that makes the urine acidic - or get dehydrated and there is a build up uric acid in the bladder. Within a short period of time when the acidic urine gets into your bladder, the E.coli in there burst into a frenzied multiplication cycle, doubling their colony size over the next 20 to 30 minutes [See]. They use up the acids in your urine in the process, and pass alkalis and endotoxins into the urine. As the urine becomes more alkaline, and the bacteria are effectively living in their own waste, they gradually become semi-dormant, slowing down their multiplication rates by as much as 100%. You take another drink of Cranberry or eat some more cranberry tablets, and start the process off again. It's not that they can't metabolise alkalis, but they don't seem to be so efficient at that.

It's a known fact that many people get bacterial cystitis when they are dehydrated and thus build up a high level of urea (uric acid) in the urine. There must be some bacteria present for any bacterial infection, but the cystitis happens because the bacteria have been given the acidic environment in which to multiply out of control. You get a feel for the hardiness of E.coli when you consider that urea is a powerful antiseptic. E.coli says "Hmm, I like that. Please can I have some more urea?..."

By avoiding cranberry, vit C in the form of ascorbic acid, alchohol, red meat and coffee, and making the urine more alkaline [See] you take away the acids that are one of the bacteria's primary sources of nutrition, effectively starving them. Better to use a citrate salt like potassium citrate, magnesium citrate, calcium citrate or sodium citrate to make the urine more alkaline. But as always, consult a good nutritionist about any dietary changes.

But Cranberry Always Seems to Help at First!

When you first take cranberry, it kills off any bacteria that cannot survive the acidic environment, and in any colony of bacteria there will be some ‘weaklings’. So cranberry usually provides very temporary relief that is followed by considerable worsening of the symptoms. This is logically because the bacteria that weren't killed off produce, when they multiply, more bacteria that like the acidic environment, and if you didn't already have acid loving bacteria in the first place, because uropathogens are very fast mutators, they are likely to produce mutations that can make better use of the acidic environment than the original cranberry survivors. This is the similar to the reproductive mechanism that produces antibiotic resistant bacteria.

Until very recently it was believed that the acid in cranberry killed the uropathogens. But that's not what happens. As explained, they adapt quickly to acidic conditions. The adaptation is by survival and multiplication, so you just end up with tougher E.coli. [See]

If you have even once had a bladder infection or UTI, taking cranberry makes it more likely that further infections will follow, because there are likely to be some remaining bacteria in the bladder behind biofilms under the surface skin of the bladder, just waiting for the right conditions to start multiplying again. [See] And as explained, once they get into your urine again, they feed on the acids cranberry provides.

Now, how mad does this make you? You get a first time urine infection - you get antibiotics. You take cranberry at the same time, and because you are helping the bacteria to grow, and making them tougher, the antibiotic fails. You go for more antibiotics, drink even more cranberry, and here you are now reading this page, still with problems perhaps years later...

But the principle of preventing adhesion works. For example, a simple monosaccharide (a rare sugar) called dmannose has up to fifty times the antiadhesion properties of cranberry, and you also get the advantage of not acidifying your urine (or your stomach for that matter). But if you try taking cranberry at the same time, you will stop the mannose from working. How do we know that? Well, almost everyone who has told us they've been taking cranberry at the same time as d-mannose, hasn't been getting better. And as soon as they stopped the cranberry, they started getting better.

Note: The above information refers to gram-negative bacteria like E.coli and Klebsiella. This covers the vast majority of bladder infections. However, cranberry may be slightly useful against Proteus type infections. Unlike E.coli, Proteus types generally multiply slower in acid urine, [you can deduce this logically from the fact that P. mirabilis produces urea, which is their 'waste' product. Nothing enjoys living in its own waste...] So basically it's doing the exact opposite of E.coli, which produces alkalis. Summarising, this boils down to the fact that if you have a Proteus infection, cranberry and vit C might not casue as many problems as it does for people with the more common infections. To reinforce this point, Sweet Cures, who produce Waterfall D-Mannose, (used for urinary tract infections) have pointed out that only two customers out of tens of thousands over five years have said cranberry was actually helping them, and both of those turned out to have Proteus mirabilis infections.

You are more likely to get proteus if you have recently been catheterised in hospital, or had a bladder operation. [See] But if you are one of the few for whom DMannose doesn't cure your problem - and you don't have a bladder prolapse or something, you need to have the bacteria that are affecting you properly checked at a lab. If it is Proteus, also ask which type - the susceptibility of Proteus to particular antibiotics varies with type. The doctor will be doing guesswork unless he/she knows enough detail about what is affecting you.

Evidence Base

The evidence that E.coli survive acidic environments is plentiful. A search on Google Scholar provides plenty of examples. However, here are some to start with.

This example is interesting because most people eat meat, or vegetables that may be contaminated with bacteria from meat. It shows that E.coli can survive stomach acid and therefore populate the gut, from where, of course, they can get into the environment and up the urethra to your bladder, there to live in comfort. They might even build a home there...

The following one contains this:

"In humans, the normal stomach has a pH of 2, which is highly acidic. The acid environment kills most pathogens. However, if the pathogen is acid tolerant, the stomachdoes not produce enough acidity or the person is taking antacid tablets, the harmful organism can slip past the stomach acid barrier and cause disease. In humans, pathogenic E. coli can cause intestinal bleeding, severe diarrhea and kidney failure. "


And this one about 'extremeophiles' contains the following:

"Gastrointestinal pathogens and human health Other microbes, while not acidophiles, are studied because their acid-resistance systems allow them to survive the low pH in our own stomachs and cause disease. Two such microbes are Escherichia coli, a well-known gastrointestinal pathogen, and Helicobacter pylori, which causes stomach ulcers."

This site does not intend to be completely negative about the effects of cranberry. In fact, cranberry can be useful for dissolving tooth enamel, (and so could possibly be used for etching teeth prior to some treatment), or for preparing some surfaces for gluing. It is especially useful for cleaning coins. However, do not use this treatment on rare coins.

Also see related news items at Healing Well

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