More evidence suggests cranberry can help prevent bladder infection

Cranberry has been held up as a herbal remedy for cystitis (urinary tract infections or ‘UTIs’) for as long as I can remember. Cranberry is believed to contain substances that inhibit the adherence of unwanted organisms such as the bacterium E. coli tothe inside of the bladder. This help prevent infecting organisms setting up camp in the bladder, enabling their clearing from the body through urination.

In a recent study published in the Journal of Agriculture and Food Chemistry, the ability of cranberry to prevent E. coli adherence was formally assessed. A group of women were treated with either 400 mg or 1200 mg of dried cranberry juice each day for a period of 8 weeks. While the 400 mg dose of cranberry had no effect on E. coli adherence, the larger dose did. This effect would be expected to reduce the risk of actual UTI. In the article I have added below, I have included some evidence which supports the notion that cranberry can indeed help prevent not just micro-organism adherence, but actual risk of infection too. In a recent review of relevant studies, cranberry products were found to reduce the risk of UTI by about a third over the course of a year [2]. The article also discusses some other simple strategies that can help prevent UTIs.

The researchers involved in the recent Journal of Agriculture and Food Chemistry study did not just assess bacterial adherence, but also measured levels of ‘oxidative stress’ in the blood of participants. Basically, this mean they measured blood levels of markers that are believed to give an indication of the level of damaged reeked by destructive molecules known as ‘free radicals’ in the body. The higher doses of dried cranberry used in this study were found to reduce levels of oxidative stress, and this may have broad implications in the long term with regard to the risk of chronic health conditions such as cardiovascular disease (e.g. heart disease and stroke) and cancer. This should not come as too much of a surprise though – cranberry is a fruit, after all.

The popularity of cranberry has tended to manifest as an almost unquenchable thirst for cranberry juice. Personally, I am not a fan of fruit juices, essentially on account of their highly sugary nature. Cranberry juice is stacked with sugar, and the ‘lighter’ versions will contain artificial sweeteners I would warn people off. Eating fresh cranberries is not really an option: even if you can get hold of them, they are extremely tart (that’s one of the reasons so much sugar/sweetener ends up being added to cranberry juice). This is one of those instance where supplementation with a preparation of the fruit makes sense. Suitable supplements may be found in health food stores and some pharmacies.


1. Valentova K, et al. Biosafety, antioxidant status, and metabolites in urine after consumption of dried cranberry juice in healthy women: a pilot double-blind placebo-controlled trial. J Agric Food Chem 2007;55(8):3217-24

2. Jepson RG, et al. A systematic review of the evidence for cranberries and blueberries in UTI prevention. Mol Nutr Food Res. 2007;51(6):738-45

Preventing urinary tract infections – 17th March 2002

Antibiotics are widely regarded as one of the great success stories of the last century. And rightly so: since their introduction into medical practice just a few decades ago, they have revolutionised the treatment of conditions such as pneumonia and meningitis, and countless lives have been saved. Despite their undoubted place in modern medicine, there is growing concern that the widespread use of antibiotics is leading to the emergence of an increasing number of superbugs ” infectious organisms that are immune to the effect of antibiotic drugs. Because of this, doctors are being urged to curb their antibiotic prescribing habits. It appears that the gleaming reputation of what have been widely regarded as the wonderdrugs of modern medicine have become somewhat tarnished of late.

Given current medical thinking, it makes sense for us to give natural approaches to common infections due consideration. Infection in the bladder, commonly referred to as cystitis, deserves special mention here. This problem affects more than half of all women at some point in their lives, and it is the second most common reason for antibiotic treatment in this sex. However, the good news is that natural help for cystitis is at hand. In this respect, traditional herbal medicine has put much faith in cranberry, and this tart little fruit has been lauded as an effective treatment for cystitis since way before the antibiotic age. Recent evidence suggests that the beneficial properties of cranberry are not merely the stuff of folklore either. Scientific studies have shown that cranberry can help to protect against cystitis and reduce the need for antibiotic treatment in the long term.

Cystitis, the medical term for which is urinary tract infection (UTI) is almost always caused by bacterial organisms. Typical symptoms of this condition are discomfort on passing water and frequent and/or urgent urination. The vast majority of UTIs are caused by an organism called Escherichia coli (E. coli). E. coli makes its way into the bladder from the outside by migrating up the urethra ” the tube that takes urine from the bladder to the outside. However, even if E. coli does manage to get access to the bladder, it has to stick to the bladder wall before it can set off a full-blown infection. E. coli has the ability to form finger-like projections called fimbriae, and it uses these to literally grab hold of the bladder lining.

One simple measure that can be taken to keep E. coli from infiltrating the bladder is to drink plenty of water. This, quite simply, tends to flush the organism out of the urethra and bladder before it gets a chance to take get a grip here. About 1½ – 2½ litres of water each day is probably enough to exert significant protective effect here. Urinating as soon as possible after sexual intercourse is of particular importance, because sex increases the risk of E. coli being introduced into the urethra and bladder.

As an adjunct to these simple measures, cranberry appears to offer real potential in protecting against cystitis. Cranberry is rich in substances called proanthocyanidins which reduce E. coli’s ability to form fimbriae, thereby preventing it from getting its sticky little fingers into the bladder wall. The evidence suggests that this disabling effect of cranberry can dramatically reduce the risk of UTIs. In one study a daily dose of 300 mls of cranberry juice effectively halved the number of UTIs and the need for antibiotics in a group of women. More evidence for the benefits of cranberry came from a study recently published in the British Medical Journal. Here, 50 mls of a concentrated mix of cranberry (and some added lingonberry) juice taken each day also halved the number of bladder infections.

2 Responses to More evidence suggests cranberry can help prevent bladder infection

  1. Elizabeth Henry 5 July 2007 at 2:18 pm #

    There was an article written in April about an herbal medicine, called Forskolin, which has shown to be very helpful in treating Urinary Tract Infections (UTIs). Forskolin is made from the Asiatic coleus plant and has been used for medicinal purposes in Asia for many years. Duke University conducted a study testing the efficacy of Forskolin on E.Coli, the root of most bladder infections. They found Forskolin to reduce the level of bacteria in the bladder as well as lessen the number inflammatory cells in urine. Additionally, Forskolin works much like cranberries, by forcing bacteria out of the lining of the bladder where antibiotics could take effect.

    Elizabeth Henry
    Natural Standard Research Collaboration

  2. Nancy 6 July 2007 at 5:52 pm #

    What would be your opinion of fruit leathers using cranberries?
    I have often cooked cranberries with apple, pureed, then dehydrated it. The apple adds enough sweetness that additional sweetener is unnecessary.
    I also find that raw cranberries, a few, are reasonably edible. Already thinking of dehydrating pureed, raw cranberry apple to see what it would be like.

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