Cranberry juice has long been touted as a natural remedy for preventing and treating urinary tract infections (UTIs). I and other contributors to this blog have written several posts about it over the past decade. I called it an alt-med zombie in 2013 and again in 2016, and here it is, back again in 2025. Over the years, research has showed mixed results, with some studies suggesting a potential benefit while others finding little to no effect. Compared to many other alternative medicine treatments, new evidence in the form of randomized controlled trials continue to emerge, so I wanted to use this post to look at the current state of the evidence to see if this popular natural product can help reduce the risk of UTIs.
Any folk remedy guide from the past 40 years will likely mention the use of cranberries and cranberry juice to prevent or treat urinary tract infections. It may be used as a supplement (as juice, extract, or capsules) to prevent or treat urinary tract infections (“acute cystitis”). A scientific reason why cranberry might prevent or treat urinary tract infections is still lacking despite over five decades of study. Is it because the berries are so bitter, that they must be medicinal? An early hypothesis may have been the ability of cranberry to lower urinary pH, which was thought to help treat UTI. Later, an ingredient in cranberry, proanthocyanidins, was thought to block some variants of E. coli bacteria from adhering to bladder cells, which has been proposed as the mechanism by which it reduce the risk of infection.
There’s another significant issue with cranberry juice as a medicine: The calorie load. Unsweetened cranberry juice is unpalatable, so it’s usually sweetened. You’d need to consume about 500mL of cranberry cocktail to obtain the typical amount studied in clinical trials. Two cups of cocktail supplies 52 grams of added sugars per day. Over a year, that’s 41 pounds of added sugar you’re putting in your diet to prevent a urinary tract infection, unless you’re taking a low-calorie version, or capsules. Capsules have been studied (although there is less evidence than with the juice) and it’s not clear that they are comparable, though one RCT found no difference. So even if cranberry juice was show to be an effective treatment, the benefits and harms need to be considered carefully.
I will skip a review of evidence to treat UTIs. In short there is no convincing evidence that cranberry juice is useful once an infection is present. The evidence is more interesting for the prevention of UTIs. There have been several systematic reviews over the past few years which I haven’t blogged about previously.
An updated Cochrane Review
The largest systematic review is a Cochrane review (updated 2023) that included 50 randomized controlled trials with 8857 patients. And it’s a positive review – with a bunch of caveats. Forty‐five studies compared cranberry products with placebo, water or no specific treatment in six different groups of participants. Twenty‐six of these 45 studies could be combined into a meta-analysis. The proanthocyanidin content varied significantly per dose, from 2.8mg to 118 mg. With moderate certainty, cranberry products were estimated to reduce the risk of UTIs by about 30%. When groups were analyzed, the following was observed:
- In women with recurrent UTIs (8 studies), the infection rate was 18% vs. 24% for placebo, meaning you’d need to treat 17 women for one to benefit (NNT=17).
- The was larger effect in children with past UTIs (5 studies), the infection rate was 16% vs. 34% for placebo, giving an NNT of 6.
- In adults following pelvic radiation and surgery, infections rates were 11% versus 23%, giving NNT of 9.
- No benefit was found in institutionalized adults, pregnant women, or those with intramuscular dysfunction.
There were no meaningful differences in adverse effects between the cranberry and the placebo groups.
There are some cautions to consider when interpreting these results. There appears to be the presence of publication bias in cranberry data, which suggests the efficacy may be overestimated. In addition, larger RCTs showed a smaller effect compared to smaller RCTs.
So are cranberries a reasonable alternative to antibiotics, which are the usual treatment to prevent UTIs in those that experience recurrent infections? Antibiotics are very effective, reducing the risk of recurrent UTIs from 66% to about 12% when taken over 6-12 months. However, they can cause side effects (15% vs. 8% with placebo) and the effects on long-term bacterial resistance are not well studied.
The Berry Bottom Line
One of the most interesting parts of medicine is seeing it progress and seeing practice change as evidence emerges. Cranberries are not a groundbreaking panacea as a medicinal product, but there appears to be something there. Recognizing the limitations of the data, cranberries may be effective at preventing UTIs. They have not been shown to be effective in everyone, which increases my skepticism about whether these efficacy findings are real. Having said that, if a patient with recurrent UTIs (not pregnant, institutionalized or with neuromuscular dysfunction) wanted to try cranberries instead of antibiotics, I would be cautiously supportive, noting that cranberries are not a slam dunk and may not be effective. But if an individual was adamant about avoiding daily antibiotics, then cranberries may be a reasonable option to try.