Cranberry juice has been used medicinally for centuries. Our new research indicates it should be a normal aspect of urinary tract infection (UTI) management today.
Authors
Christian Moro
Associate Professor of Science & Medicine, Bond University
Charlotte Phelps
Senior Teaching Fellow, Medical Program, Bond University
While some benefits of cranberry compounds for the prevention of UTIs have been suspected for some time, it hasn't been clear whether the benefits from cranberry juice were simply from drinking more fluid, or something in the fruit itself.
For our study, published this week, we combined and collectively assessed 3,091 participants across more than 20 clinical trials.
Our analysis indicates that increasing liquids reduces the rate of UTIs compared with no treatment, but cranberry in liquid form is even better at reducing UTIs and antibiotic use.
Are UTIs really that bad?
Urinary tract infections affect more than 50% of women and 20% of men in their lifetime.
Most commonly, UTIs are caused from the bug called Escherichia coli (E.coli). This bug lives harmlessly in our intestines, but can cause infection in the urinary tract. This is why, particularly for women, it is recommended people wipe from front to back after using the toilet.
An untreated UTI can move up to the kidneys and cause even more serious illness.
Even when not managing infection, many people are anxious about contracting a UTI. Sexually active women, pregnant women and older women may all be at increased risk.
Why cranberries?
To cause a UTI, the bacteria need to attach to the wall of the urinary bladder. Increasing fluids helps to flush out bacteria before it attaches (or makes its way up into the bladder).
Some beneficial compounds in cranberry, such as proanthocyanidins (also called condensed tannins), prevent the bacteria from attaching to the wall itself.
While there are treatments, over 90% of the bugs that cause UTIs exhibit some form of microbial resistance. This suggests that they are rapidly changing and some cases of UTI might be left untreatable.
What we found
Our analysis showed a 54% lower rate of UTIs from cranberry juice consumption compared to no treatment. This means that significantly fewer participants who regularly consumed cranberry juice (most commonly around 200 millilitres each day) reported having a UTI during the periods assessed in the studies we analysed.
Cranberry juice was also linked to a 49% lower rate of antibiotic use than placebo liquid and a 59% lower rate than no treatment, based on analysis of indirect and direct effects across six studies. The use of cranberry compounds, whether in drinks or tablet form, also reduced the prevalence of symptoms associated with UTIs.
While some studies we included presented conflicts of interest (such as receiving funding from cranberry companies), we took this "high risk of bias" into account when analysing the data.
So, when can cranberry juice help?
We found three main benefits of cranberry juice for UTIs.
1. Reduced rates of infections
Increasing fluids (for example, drinking more water) reduced the prevalence of UTIs, and taking cranberry compounds (such as tablets) was also beneficial. But the most benefits were identified from increasing fluids and taking cranberry compounds at the same time, such as with cranberry juice.
2. Reduced use of antibiotics
The data shows cranberry juice lowers the need to use antibiotics by 59%. This was identified as fewer participants in randomised cranberry juice groups required antibiotics.
Increasing fluid intake also helped reduce antibiotic use (by 25%). But this was not as useful as increasing fluids at the same time as using cranberry compounds.
Cranberry compounds alone (such as tablets without associated increases in fluid intake) did not affect antibiotic use.
3. Reducing symptoms
Taking cranberry compounds (in any form, liquid or tablet) reduced the symptoms of UTIs, as measured in the overall data, by more than five times.
Take home advice
While cranberry juice cannot treat a UTI, it can certainly be part of UTI management.
If you suspect that you have a UTI, see your GP as soon as possible.
The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.
