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Updated July 30, 2015.

Question: My family doctor says cranberries are useless in helping with urinary problems such as bladder infections. Do you agree?

Joe - About.com User

Answer: I'd say current evidence indicates a 'definite maybe.'

Cranberry juice may help to prevent some urinary tract infections in women who are prone to these infections, but beyond that, there probably isn't much value as far as urinary problems are a concern.


 And, to receive that benefit, women need to drink 7 ounces of plain cranberry juice every day or take cranberry supplements. 

Urinary tract infections can be quite painful. Women may feel like they need to urinate frequently, have a burning pain while urinating, and may even see blood in the urine. Medical treatment is needed for cystitis and involves antibiotics when bacteria are present.

So how can cranberries help?

Cranberries (and blueberries) contain a bunch of different antioxidant compounds, including anthocyanins, flavonols, terpenes, hydroxycinnamic and hydroxybenzoic acids, resveratrol and some vitamins and minerals.

There's actually been a number of studies done on cranberries -- including lab studies that have examined some of those antioxidants to see if they have an impact on the bacteria that causes more urinary tract infections -- E. coli. 

Originally, the thought was that benzoic acid found in cranberries made the urine more acidic and that the lower pH allowed other compounds -- possibly hippuric acid -- to kill off the offending bacteria.

 

But it turns out there's just not enough benzoic acid in cranberries. Or hippuric acid. So that hypothesis went down the drain.

Since cranberries don't kill the bacteria, scientists decided to see if it prevented the E coli from sticking to the walls of the urethra and bladder. If the bacteria can't take hold, then infection is less likely.

More research was done in the lab -- and in people -- and the findings led scientists to believe that some of the proanthocyanidin polymers in the cranberries reduce the stickiness of the bacteria. 

But while those studies looked promising, they couldn't measure the ability of cranberries to prevent full-on urinary tract infections -- that required clinical studies.

There are, actually, some clinical studies on cranberries and urinary tract infections back in the 1960s, when some women who drank cranberry juice had fewer bacteria in their urine and a reduction of symptoms. But, it wasn't a good study design -- no placebo or control group.

A study was published in 2001 that compared recurrence of urinary tract infections in women who drank a combination of lingonberry and cranberry juice with women who took a probiotic drink (and a control group who did nothing). The results looked promising, and cranberry juice became a bit more trendy.

But since then, the evidence has dwindled as new studies have reported their findings. That's not uncommon -- often a food or lifestyle change looks really awesome in early studies, but as more researchers dig in deeper, the results regress a bit.

So, while more studies might change my mind, for now I'll stand by my 'definite maybe' that it's possible cranberry juice consumption might help reduce the risk of urinary tract infections in women who are prone to them. But, it's important to speak with a health care provider.

Preventing Urinary Tract Infections

• Go ahead and drink seven ounces of cranberry juice daily. Remember to buy 100-percent cranberry juice, not cranberry juice drinks or cocktails because they contain much less cranberry juice and a lot of sugar.
• If you prefer, you can take cranberry juice tablets. Be sure to follow the instructions on the label.
• Drink plenty of water. When you drink more water, you will urinate more often, which helps flush the urethra and remove the bacteria.
• Wipe your genital area from front to back after urinating or having a bowel movement to help keep bacteria from the vagina and anus away from your urethra.
• Take showers instead of baths.

Please not that while research supports that cranberry juice prevents urinary tract infections in women, it may not be true for men or children. Speak with your doctors if you're taking medications -- drinking large amounts of cranberry juice may interact with some drugs.

<sub>Source:

Vasileiou I, Katsargyris A, Theocharis S, Giaginis C. "Current clinical status on the preventive effects of cranberry consumption against urinary tract infections." Nutr Res. 2013 Aug;33(8):595-607.</sub>