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Ouch: Cranberry Juice Is No Cure for Bladder Infections

Doctors were told they do their patients a ‘disservice’ by recommending it


I prefer my placebos to be cheap and tasty, and it looks like cranberry juice fits the bill. Long touted for its ability to prevent urinary tract infections, there is now a bog of evidence suggesting that cranberry juice cannot kill, maim, disable or even drown the bacteria that can infect the human bladder.

Which is too bad, both for the cranberry growers of Wisconsin (who produce 60 percent of our nation’s cranberry crop) and for the multitudes who develop urinary tract infections (UTIs). In 2007, 8.7 million people — mostly women — made a clinic visit for a UTI, making it the most common bacterial infection seen outside the hospital. On the other hand, cranberry growers are relatively scarce, except in central Wisconsin.

Promoting the Juice Goes ‘Beyond Rational Reasoning’

An editorial in The Journal of the American Medical Association last November reviewed the data on cranberry juice and UTIs. It concluded: “Any continued promotion of the use of cranberry products seems to go beyond available scientific evidence and rational reasoning.”

Unfortunately, the ability of cranberry proanthocyanidins to block E.coli’s grip in lab research didn’t seem to play out in the real world.

Although the word “malpractice” never appears, the editorialist recommended that “…clinicians should not be promoting cranberry use by suggesting that there is proven, or even possible, benefit. Clinicians who encourage such use are doing their patients a disservice.” Which makes me wonder; Could I be sued for offering a disservice to my patients?

In any case, if my patients or I will take a placebo, I also prefer that it have a compelling story — a reason why it possibly could, or just maybe might, potentially work. Initially, the cranberry benefit was attributed to its acidic quality: acidification of the urine would make the bladder and the rest of the urinary tract too hostile an environment for bacteria to live in.

Unpronounceable, But Beneficial for a Bladder Infection?

But then the focus turned to a group of compounds called “proanthocyanidins,” a class of nutrients found in cranberries — and also in pine bark, grape seeds and skins, black currants, green and black tea and the elusive bilberry. Proanthocyanidins belong to the larger flavonoid family, which are water-soluble plant pigments that we suspect are one of the reasons why diets high in fruits and vegetables are so healthy. Unfortunately, taking these compounds in pill form doesn’t appear to be effective. As is often the case with nutrition, the food itself seems to hold the magic.

Some earlier research suggested that the proanthocyanidins in cranberries could block the ability of bacteria to bind to the cells that line the bladder wall. That’s a critical step in a urinary tract infection, because urine is a food desert where it’s tough for even bacteria to survive. Like a medieval battle, you have to get inside the castle if you want the good stuff; and the moat is an impediment.

Working in the Lab, Not Your Bladder

Escherichia Coli (E.coli, the bacteria that’s by far the most common cause of bladder infections) and other bacteria have a cache of biological tools to help them first attach to the cells lining the urethra and the bladder. They then extract from those cells the nutrients they need to replicate — all while warding off soldiers from our immune system.

Unfortunately, the ability of cranberry proanthocyanidins to block E.coli’s grip in lab research didn’t seem to play out in the real world. If you want a sense of how unbelievably complicated this microscopic urological battle scene is, try reading through this review article in Nature Reviews Microbiology. Or this one in Nature Reviews Urology, which describes the seesaw battle over the nutrient iron, which is critical to a bacteria’s ability to thrive and replicate.

One of the compounds that bacteria make to procure iron is enterobactin. But white blood cells counterpunch by making lipocalin-2, a protein that inactivates enterobactin and starves E.coli of its iron.

But some bacteria can modify their enterobactin so it can no longer be deactivated by lipocalin-2 (advantage E.coli!). And so the battle rages on. If cranberry proanthocyanidins do indeed inhibit bacteria’s ability to stick to the bladder wall, it clearly isn’t enough to turn the battle.

What Does Help?

So, if cranberry juice is out, what’s still in?

A 2012 review in The New England Journal of Medicine offered some potential behavioral strategies for preventing UTIs.

Because sexual intercourse is the strongest risk factor for UTI, the authors recommended “abstinence or reduction in frequency of intercourse,” at the same time recognizing that “often this behavioral strategy is not feasible.” Hmm… I think feasible strategies are the best kind of strategies.

They followed with a strong recommendation against using spermicides for birth control, and then provided a list of suggestions they admitted posed a low risk [of causing side effects or other problems] but “might be effective”: urinate soon after intercourse, drink fluids liberally, don’t routinely delay urination, wipe front to back after defecation, avoid tight-fitting underwear and avoid douching.

If I am I doing my patients a disservice by recommending cranberry juice, am I also doing them a disservice by prescribing a list of scientifically plausible, but scientifically unproven, behaviors? Or is it something more? Because I don’t want to get sued.

How about trying a pine bark, bilberry smoothie? We don’t know that it wouldn’t work …yet.

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By Craig Bowron, MD
Dr. Craig Bowron is a physician and writer in St. Paul, Minn., whose articles have appeared in Slate, the Washington Post, Huffington Post, Minnesota Monthly and other publications. Find him at CraigBowronMD.com.@billcarlosbills

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