Many of us know cranberries as a tasty condiment with our Christmas turkey, or the juice that accompanies vodka in a cosmopolitan cocktail. You may also have heard of cranberries prevent urinary tract infections (UTIs).
Although this is often dismissed as a myth, ours reassessment of the evidence shows that consuming cranberry juice or supplements reduces the likelihood of recurrent UTIs for women, children, and those more susceptible to them due to medical procedures.
But this was not the case for the elderly, pregnant women or people with bladder emptying problems.
The review did not look at the use of cranberry for the treatment of urinary tract infections – and cranberry juice cannot cure a UTI alone. So if you do get a urinary tract infection, make sure you seek medical help from your GP or other healthcare provider.
Remind me, what is a urinary tract infection?
UTIs are unpleasant and common. About a third of women will have one at some point in their lives. They are also common in the elderly and people with bladder problems caused by spinal cord injury or other conditions.
Typically, a urinary tract infection feels like razor blade urination and the urine can be foul-smelling, cloudy, and sometimes contain blood. Other symptoms include the frequent urge to urinate, a stinging or burning sensation when urinating, and pain in the lower abdomen or pelvis.
UTIs are caused by bacteria. Normally, bacteria do not live in the urinary tract, but when they do, they stick to the bladder wall, multiply and can cause a urinary tract infection.
If a urinary tract infection is left untreated, the infection can travel to the kidneys and, in the worst case scenario, cause complications such as severe pain or sepsis (a blood infection).
Most urinary tract infections are effective and easy to treat with antibiotics. Sometimes just one dose of antibiotics can clear up the infection. Unfortunately, urinary tract infections keep coming back in some people.
What medicinal properties do cranberries have?
The First Peoples of North America have long known the benefits of eating cranberries, including their benefits for bladder problems.
More recently in the the 80’s And the 90’slaboratory scientists began to investigate several plausible explanations for these benefits.
The most widely accepted explanation is their high concentration of the antioxidant proanthocyanidin. cranberries (Vaccinium macrocarpon) – a fruit native to North America – have a high concentration of proanthocyanidin, which protects the cranberry plant against microbes.
Researchers think the compound also prevents the most common UTI-causing bacteria – Escherichia coli (E coli) – from sticking to the bladder wall.
It was this apparent ability that researchers concluded was responsible for the cranberry’s medicinal properties.
However, without strong evidence of how or if cranberry worked, health care providers were left without clear guidance on who might benefit from cranberry. As a result, the ongoing debate in academic literature has lasted for more than 30 years.
Read more: Phytonutrients can boost your health. Here are 4 and where to find them (also in your next cup of coffee)
The evolution of the evidence
Researchers periodically review the evidence supporting tests, treatments, and interventions for a variety of health conditions.
Proving efficacy became a focus with the publication of randomized trials starting in 1994. The first Cochrane compilation of four clinical trials on this topic – published in 1998 – concluded that the evidence was too weak to establish efficacy.
A Cochrane Review involves identifying all available peer-reviewed academic evidence on a health care or health policy topic. The evidence is reviewed independently and in an unbiased manner by members of the Cochrane Networka network of independent researchers, professionals, patients and carers interested in answering health questions.
Updates in 2004 and 2008 suggested that cranberry products reduced the risk of repeated urinary tract infections in women, but most of the studies were not considered high-quality evidence, so the findings were inconclusive.
by 2012, the amount of evidence had increased to 24 clinical trials, but the data was inaccurate and the conclusions were that cranberry juice had no benefit.
As one of Cochrane’s most popular reviews, and the ever-increasing body of evidence, updating the review was important.
Over time, research has improved on the consistency of how cranberry is consumed — as juice or tablets — as well as on effective dosage measurement and estimates of how much active ingredient (proanthocyanidin) is in the various products.
Us Cochrane reviewupdate, published this week, now lists 50 clinical trials of cranberry products.
More than 8,800 people participated in the clinical trials where people were randomly assigned to take either cranberry products or a dummy treatment – either a placebo (a substance that has no therapeutic effect) or “usual care” (where people may be given a different preventative product , such as probiotics).
The recently increased body of high-quality evidence has shown that cranberry products work for people who experience recurrent UTI or are prone to UTI. Recurrent UTIs are defined as two or more urinary tract infections within six monthsor three or more urinary tract infections within a year.
Cranberry products reduce the risk of recurrent symptomatic culture-verified (lab-tested) UTIs in women (by approximately 26%), children (by approximately 54%), and those susceptible to UTI following medical interventions (by approximately 53%) %).
The findings don’t concern people who get UTIs infrequently but want to avoid them.
Read more: Should pharmacists be able to prescribe common medicines like antibiotics for urinary tract infections? We asked 5 experts
What is still unclear is the formulation and dosage of cranberry products. The evidence failed to clarify whether cranberry tablets or liquids are more effective, what dosage of cranberry works best, or how long people need to take cranberry products to get the full benefits. The clinical studies varied in the duration of cranberry consumption, from four weeks to 12 months.
One of the many complicating issues addressed in this update was who funded each trial. Each clinical trial was classified as either supported by funds from commercial organizations (such as a juice manufacturer) or conducted by non-profit organizations (such as universities or hospitals) that paid for their own cranberry product.
However, we found no difference in the results for clinical trials supported by juice manufacturers compared to those conducted by academic institutions.