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Home » Does cranberry juice really treat a UTI? Let’s check the science

Does cranberry juice really treat a UTI? Let’s check the science


It’s that time of year when Americans have cranberries and turkey, which made me wonder if the belief that cranberry juice could treat a UTI (urinary tract infection). Now, I love cranberry sauce — yes, I love the stuff that comes out of the can, and I will die on that hill, though I’m not a fan of the juice version. But I’ve had girlfriends who swear by cranberry juice for treating a bout of UTI.

I kept hearing about this magical curative power of cranberry juice for decades. So much so, that I began to wonder if it was just one of the myths that are repeated so often that we think they are a fact. Or is it supported by real science? You know, like the old adage that sugar causes your children to be hyper, which proved to not be supported by any science.

Well, your cranky old dinosaur wanted to find out whether it was a myth or science, so I jumped into cranberry bog with both feet.

All about cranberries

I actually jumped into this topic because of the YouTube video I watched above. It was all about how farmers raise and harvest cranberries. It’s kind of cool.

Cranberries are a group of evergreen dwarf shrubs or trailing vines in the subgenus Oxycoccus of the genus Vaccinium. Cranberries are found in acidic bogs throughout the northern hemisphere, though The USA and Canada cultivate and produce more cranberries than the rest of the world combined.

Cranberries are low, creeping shrubs or vines up to 2 meters (7 ft) long and 5 to 20 centimeters (2 to 8 in) in height they have slender, wiry stems that are not thickly woody and have small evergreen leaves. The fruit is a berry that is larger than the leaves of the plant. The berry is initially light green, turning red when ripe. It is edible, but with an acidic taste that usually overwhelms its sweetness. It’s usually described as tart.

Contrary to what you might think, the cranberry plant does not grow in standing water. The cranberry fields are flooded for harvest only. When it’s flooded, machinery removes the berry from the bush, which then floats on the water. These floating berries are literally suctioned from the top of the flooded field, and fed into trucks.

In the USA, a farmer’s cooperative, Ocean Spray, is responsible for nearly all of the production of cranberries into my favorite canned jellies or into juice. Even unprocessed cranberries generally come from the cooperative.

So, there you go, you now probably know more about cranberries than you ever wanted.

close up of strawberries
Photo by Irita Antonevica on Pexels.com

What about cranberry juice and a UTI?

Let’s now get into the science of cranberry juice. Raw cranberries, cranberry juice, and cranberry extracts are a source of polyphenols — including proanthocyanidins, flavonols, and quercetin. It is thought that polyphenols might have an effect on some cancers, the cardiovascular system, and the immune system, but there is little robust evidence support any clinical effect.

As expected, there is a lot of research that has attempted to show a causal link between cranberry juice and the treatment or prevention of UTIs. And lucky for us, there are several systematic reviews and meta-analyses (which are considered to be at the top of the hierarchy of clinical research) that have examined the potential link between cranberry juice and the treatment of a UTI. Let’s take a look at these systematic reviews and meta-analyses.

In a systematic review from Cochrane, the researchers concluded:  

There was some evidence to show that cranberries (juice and capsules) can prevent recurrent infections in women. However, the evidence for elderly men and women was less clear, and there is evidence that is not effective in people who need catheterisation. Many people in the trials stopped drinking the juice, suggesting it may not be a popular intervention. In addition, it is not clear how long cranberry juice needs to be taken to be effective or what the required dose might be.

Now, I’m not taking this as overwhelmingly positive evidence that cranberry juice works for UTIs, but it’s positive for preventing recurrent infections in women.

In a systematic review and meta-analysis of clinical trials, the researchers concluded:

The results of the current study could be used by physicians to recommend cranberry ingestion to decrease the incidence of urinary tract infections, particularly in individuals with recurrent urinary tract infections. This would also reduce the administration of antibiotics, which could be beneficial since antibiotics can lead to the worldwide emergence of antibiotic resistant microorganisms.

Now, that’s a more definitive statement that cranberries may be effective in preventing UTIs, although it did not discuss whether it could be used as a treatment. It did imply that it could be used.

Another systematic review and meta-analysis concluded:

These results suggest that cranberry may be effective in preventing UTI recurrence in generally healthy women; however, larger high-quality studies are needed to confirm these findings.

The problem with these analyses is that they are dependent on small-sized clinical trials. As you know from reading my articles, I generally favor larger clinical trials as the statistics are more meaningful. And the results are more clinically meaningful. Furthermore, these studies focus on recurrent UTIs and not on acute, uncomplicated urinary tract infections.

A 2020 systematic review examined the effect of cranberry products on acute UTIs across several small clinical trials. The authors concluded:

The current evidence base for or against the use of cranberry extract in the management of acute, uncomplicated UTIs is inadequate; rigorous trials are needed.

This appears to be the major issue — there are no large, robust, and repeated clinical trials that have examined whether cranberry juice has an effect on an acute UTI. There seems to be good evidence that it can prevent recurrent urinary tract infections, but there is little evidence supporting its use in treating UTIs.

bowl of cranberry dessert with lemon slice and chopstick
Photo by Karolina Grabowska on Pexels.com

Summary

As a writer that relies upon science-based medicine, it was good to find a lot of large systematic reviews and meta-analyses that examined the effect of cranberry products on urinary tract infections. And here’s what I think:

  1. There seems to be compelling evidence that cranberry juice can prevent recurrent urinary tract infections. However, this is based on a few smallish clinical trials.
  2. There seems to be no good evidence that cranberry juice can treat an acute UTI. The clinical trials are too small to be definitive and taken together, they couldn’t tell us whether it worked or not.

Taken in total, the evidence is intriguing. It seems to indicate that it might work, and it certainly is safe, so eating a bunch of cranberry products is not going to cause harm. Even the jellied cranberries in the can.

Right now, I am not sure I would recommend cranberry juice to treat an acute UTI, so you might still need antibiotics from your physician. I just wish Ocean Spray would fund a large (say 5000 subject) clinical trial managed by independent researchers that would look into this issue. Because there is just enough evidence that it might work that cranberry farmers would benefit if it is in fact clinically relevant.

Time for more of that canned cranberry sauce. Yum.

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Michael Simpson
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