Does Cranberry Juice Really Help Prevent UTIs? What Does Science Say?

Drinking cranberry juice to prevent and eliminate Urinary Tract Infections (UTIs) is a popular remedy. With such a wide-held belief in the benefits of cranberry juice for UTIs, it begs the question: Does cranberry juice really help prevent UTIs?

The short answer is: Yes, it can help reduce the risk of UTIs in many people; however, its benefits may be limited in certain groups of individuals or in treating an existing infection, especially a severe one. To understand the relationship between cranberries and UTIs, it would help to get up to speed on how UTIs occur in the first place.

UTI 101

When pathogenic (harmful) bacteria, particularly E. coli, attach to and start growing in the urinary tract, it causes an infection. The infection generally causes a spike in the immune response, which, together with bacterial overload, causes painful UTI symptoms such as fever, chills, trouble/pain while urinating, etcetera. It is essential to get rid of pathogenic bacteria to ward off an infection. Antibiotics (natural or synthetic) are a gold-standard treatment to eliminate bacterial infections. However, mild cases of UTI may not need antibiotics as they can resolve on their own. Also, there is evidence that without knowing the exact bacteria type causing the infection, wrong (often ineffective) antibiotics can be prescribed.

How and Why Do Cranberries Work?

Cranberries (in the form of fruit, juice, or supplements) work in two ways to prevent and alleviate a UTI.

Cranberries are high in proanthocyanidins. These chemical compounds belong to a special class of polyphenols called flavonoids, which have antioxidant and anti-inflammatory properties. Consider them antimicrobial agents. Proanthocyanidins can prevent bacteria from attaching to the lining of the urinary tract and bladder, which stops the spread of pathogens, reducing the risk and underlying cause of UTIs.

There is another interesting way cranberries may help. The consumption of cranberries helps to lower the pH of urine, making it more acidic than usual. Acidic urine is not a conducive environment for bacteria to flourish and survive in the bladder. Therefore, it is a very effective way to prevent the occurrence of an infection in the first place.

Scientific studies on Cranberry Juice and UTI

A recently published scientific review of 50 randomized controlled trials that included nearly 9000 participants found cranberry juice and supplements to be effective in preventing UTIs in certain groups of individuals. The review, published in the Cochrane Database of Systematic Reviews, shows cranberry juice and supplements are most effective in people who experience frequent infections, children, and individuals susceptible to urinary infections due to medical interventions.

Several early-stage studies demonstrated that fructose and proanthocyanidins found in cranberries bind to E. coli bacteria proteins and prevent them from sticking to the lining of the urinary tract. One study incubated bacteria with cranberry powder containing 9 mg of proanthocyanidins per gram and added it to a lab dish of cells. The cranberry powder reduced bacteria adherence after exposure to 50 mcg/ml. However, researchers showed that the antimicrobial effect depends on the dose.

In another study, researchers grew bacteria in soy broth with a cranberry juice cocktail or proanthocyanidins. The bacteria cultures increased, but the bacteria attachment decreased. The researchers found that compounds in cranberries change the shape of surface proteins on E.coli bacteria, which stops attachment. However, bacteria eventually regained the ability to attach to cells. The effects of cranberry juice were also only maintained with higher doses or repeated use.

Limitations of Cranberry Juice for UTIs

The form in which cranberries are consumed and whether they have been altered with additives, preservatives, or other elements can significantly affect their efficacy.

Consuming raw cranberries or not-from-concentrate cranberry juice can bring about the maximum health benefits. Unripe cranberries have the highest amount of proanthocyanidins; however, they are bitter and may be challenging to consume.

Juices are usually easy to consume; however, store-bought juices are often diluted with other fruit juices, significantly reducing their efficacy. Also, research shows that the amount of proanthocyanidins in not-from-concentrate juices is significantly higher than in juices that have been reconstituted. Most commercial juices have very few of these compounds and may not produce the desired bacteriostatic effect on the body.

Another issue with store-bought cranberry juices/products is that (food) processing can destroy proanthocyanidins. Also, preservatives and sweeteners, common in commercial cranberry juices, can spoil the health benefits. So, reading the label clearly and choosing a product free from additives and sweeteners is always a good idea.

Limitation of Cranberry Juice/Supplements in Certain Groups of Individuals

Research shows that cranberry juice and supplements may not benefit specific groups of individuals against UTIs, particularly pregnant women, adults with neuromuscular bladder dysfunction that may prevent them from emptying their bladder completely, and elderly institutionalized people. It is essential to proactively monitor your symptoms and find for yourself if any therapy fails to alleviate your symptoms. Some individuals may not receive the desired effect with one remedy alone. It is essential to speak with a physician to learn if augmenting your treatment plan with supplements will be a good option or not.

Should you Consume Cranberry Juice for UTIs?

Overall, reviews of all the research suggest that cranberry juice may be a great preventative step to keep UTIs at bay. It can be effective in most individuals, especially those dealing with recurrent infections. While cranberry juice/supplements may be able to provide limited relief once an infection has started, they may not be an effective treatment for moderate-to-severe infections. Also, certain groups of people, such as pregnant women, may not benefit from cranberry supplements. UTIs during pregnancy require professional medical intervention.

Consuming anything in abnormal doses is not a good idea, which is true for cranberry juice and supplements too. Common side effects of cranberry juice may include upset stomach and nausea. Moderate consumption of cranberry products likely won't cause harm; there are other drawbacks. Cranberry juice is expensive and high in calories, and it might not even have enough proanthocyanidins to have an effect. Other over-the-counter UTI medicine, antibiotics, and self-care habits might work faster.

Still, if you want to try cranberries, you can. Tablets are likely better than juice, though. Studies recommend a standardized product with at least 36 mg of proanthocyanidins.

How much Cranberry Juice should you consume for UTIs?

The key ingredient in cranberry juice that has a bacteriostatic effect is proanthocyanidins. Your dosage of cranberry juice and supplements will depend on its proanthocyanidins levels. A daily dose of 36 milligrams of proanthocyanidins is recommended to prevent UTIs.

Cranberry juice can contain anywhere from 17.8 to 46 milligrams of proanthocyanidins in 7 ounces (200ml). Fresh not-from-concentrate cranberry juice contains a higher amount of proanthocyanidins, typically on the order of 23.0 mg /100 mL. A store-bought pasteurized reconstituted cranberry juice can contain as low as 8.9 mg/100 mL of proanthocyanidins, which means you'd have to faithfully drink about one full glass of cranberry juice twice daily to get 36 milligrams of proanthocyanidins.  

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How Quickly Does Cranberry Juice Work?

If you can get a high-quality cranberry juice or supplement containing at least 36 mg of proanthocyanidins, it can take effect 4-8 hours after consumption. Do not expect a UTI to go away right after consumption completely. Continue consuming juice/supplements and monitor how your symptoms are being alleviated. If your symptoms persist, consult with a doctor to find a remedy or prescription drug that will work for you.

Several factors, including the severity of the infection and your treatment regimen, can influence recovery from a urinary tract infection. Read more about how long a UTI typically lasts in this blog.