Cranberries may reduce the recurrence of urinary tract infections, but their role in treating infections is limited.
How could any bacteria cause a bladder infection without just getting flushed away--literally? Certainly if you're not drinking enough, or men who have prostate enlargement and can't empty completely, leaving behind a stagnant pool, but in most people there should be a constant flow of water through there. Well bladder infection-causing E. coli evolved these finger-like projections (fiubrae) that they use to stick to the walls of the bladder so they don't get washed away.
Almost 30 years ago now, it was demonstrated that if you drip cranberry juice on E. coli they don't stick as well. Grape juice doesn't work, nor does orange or apple juice, or even white cranberry juice made from unripened berries, so maybe it's one of the red phytonutrients that's doing it.
Even if it works in a petri dish, though, you don't pee cranberry juice. How do we know that the anti-adherence phytonutrients are even absorbed through the gut so they make it into the bladder? Well subsequent studies showed that if you drip the urine of someone who drank cranberry juice onto E. coli they don't stick as well either. Ah, well now we're getting somewhere. Here's the stickiness of strains of E. coli wading in urine from someone drinking water; and here's the stickiness in the urine of someone drinking cranberry juice. Within hours of consumption there's a drop in E. coli stickiness that appears to last throughout much of the day. So might cranberries really help prevent bladder infections?
Well the best way to prevent infections is to not get infected in the first place, which may involve the avoidance of chicken, as I've already discussed, so you're not constantly re-infecting yourself. But if that doesn't work, if your gut remains stubbornly colonized with these bad bladder bugs, various tested cranberry products appear to reduce the recurrence of bladder infections by about 35%, not as effective as antibiotics but doesn't foster antibiotic resistance and has fewer side effects.
There's no good evidence to suggest cranberries are an effective treatment, though, which makes sense, right? Cranberries prevent the initial adherence, but that occurs at the start of the infection, but when the infection is present and already stuck there's no clinical data to suggest that cranberries are effective in the treatment of urinary tract infections, meaning it doesn't work better than placebo, but placebos work! For example, ibuprofen seems to work just as good as antibiotics for the treatment of uncomplicated urinary tract infections.
Now some people you really do need to treat with antibiotics—pregnant women, children, men, those with kidney infections, systemic symptoms like nausea and vomiting, but for most healthy women, bladder infections just go away on their own without antibiotics. So all the women who drink cranberry juice and have their symptoms disappear may falsely attribute their recovery to the juice, but when it comes to most UTIs, nothing works! Nothing, in fact, actually works, leading doctors try to figure out how they can harness the placebo effect themselves.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Ariel Levitsky.
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The reference to poultry as the source of bladder-infecting E. coli is from my last video, Avoiding Chicken to Avoid Bladder Infections.
How can you consume cranberries palatably? Check out my recipe for Pink Juice with Green Foam.
I find it so fascinating that the white berries don't have same effect. For more on these elusive phytonutrients, see Phytochemicals: The Nutrition Facts Missing From the Label and for those doubting the power of plants, Power Plants.
I discuss the controversy around doctors giving placebos in The Lie That Heals: Should Doctors Give Placebos?
If cranberries are so good at keeping bacteria from sticking to the wall of the bladder, what about keeping bacteria from sticking to other places like our teeth? That's the subject of my next video, Childhood Tea Drinking May Increase Fluorosis Risk.
For more context check out my blogs: Does Cranberry Juice Work Against Bladder Infections? and Tea and Flouride Risk
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