The last sentence in the ‘Plain Language summary’ says “Cranberry products (such as tablets or capsules) were also ineffective (although had the same effect as taking antibiotics), possibly due to lack of potency of the ‘active ingredient’.” …What?
How could they have the same effect as antibiotics and be ineffective at the same time? Is this suggesting antibiotics are ineffective against UTIs? Aren’t antibiotics used to treat UTIs to begin with?
If someone could explain any or all of that to me, I would appreciate it greatly. My girlfriend just got a UTI and is very scared. I found this article, but it seems to contradict itself in a few places, to me. I’m not a scientist, so I recognize that I might just not be able to comprehend it, and would love some clarification!
If you got this far, I’m also wondering how these studies could be considered accurate if a lot of the subjects stopped taking the cranberry products?
TL; DR is the first two sections at the top👆
Focus on the RRs and CIs (Relative Risk and Confidence Intervals)—for example: “cranberry products did not significantly reduce the occurrence of symptomatic UTI overall (RR 0.86, 95% CI 0.71 to 1.04)”.
A relative risk lower than 1.0 suggests a reduced risk, while the 95% confidence interval is the range that the real value probably falls within, accounting for potential sampling error, study size, etc.
So an RR of 0.86 suggests that cranberry probably reduces the risk of UTI, but the top of the CI being above 1.0 means the study can’t rule out the chance that cranberry actually increases the risk. It’s that last part that presumably leads them to say that cranberry didn’t reduce the risk significantly.
Okay, that’s interesting. Thanks for the thought out response!
There’s a couple thing to keep in mind that might help it make sense. Meta-analyses, though not without merit, don’t always accomplish the intended goals for a few reasons, two of which this study specifically suffers from. The first is that they combine studies that when they were conducted may have looked at the desired treatments and controls, but they often are doing so in different populations (note they stratify results by elderly, cancer patients etc.) I’m not going to on my phone start pulling the references, but I would venture to guess that the included studies have all sorts of specific groups they were targeting which leads to heterogeniety both in effect size but in interpretation of effect size. Think about it this way, if you are using Dat from many studies with different (often very specific) target populations, does it really make sense to combine them to draw conclusions about a some hypothetical population comprised of those people?
The second thing is sample size. A few thousand seems like a lot until you realize the data in question is incidence. Each subject included either had the disease or they didn’t (it’s 0 or 1) nothing in-between and nothing outside. Interval inference for dichotomous data (especially when it gets substratified down like the authors have done here) often lead to results like the plain language summary presented. That is, everything is null because they tried to say too much, with too little data.
Takeaway is don’t read too much into the findings. The authors were certainly trying to earnestly answer the question (probably), but the existing literature and available data came up short.
I appreciate that. It’s the feeling that I got, but I don’t have any formal education on reading things like this, so I wanted some confirmation or education
I’m too tired to read the article but everyone here is commenting on cranberry’s preventative performance. There’s a difference between prophylaxis and treatment - so that’s worth clarifying in my mind.
I appreciate that, I’m looking into cranberries because apparently she’s prone to it. We just got the antibiotics a doctor prescribed, but I was looking into whether or not it actually helps prevent them
You’re a lovely partner. Anecdotally, we have someone very prone to them in our family who swears by cranberry juice.
Anecdotally my doctor tells me the concentrations of cranberry juice and supplements are far too little to help significantly and it’s basically a myth that it helps.
That said, I’m pragmatic and think you should try things and see what consistently works (while being careful in observation and testing variables - best to make it objective, to eliminate bias, etc.).
This is great advice! I appreciate it
I appreciate the sentiment and anecdotal evidence
There are vaccines coming for some strains of UTI. Some of these meds are already available in Europe.
Thank you for this! My girlfriend started looking into it, thanks to you. It seems like they’re not as effective as we’d hope, but maybe in the next couple years they will improve. We had no idea this was a thing, thank you so much!
I’ve only skimmed the abstract, but it makes me think antibiotics aren’t effective. I’m basing that on combining two findings that are explicitly stated there: cranberries don’t work, and cranberries are no different to antibiotics. Transitive inference would imply that this means antibiotics don’t work, although I’m surprised the authors haven’t been more explicit about this, given they’ve left it ambiguous and it seems like an obvious question
Edit: there’s slightly more detail at the bottom where it says “Cranberry products were not significantly different to antibiotics for preventing UTIs in three small studies.” It looks like cranberries and antibiotics were only compared in a very limited set of studies, so perhaps take the comparison with a pinch of salt
The study is comparing cranberry products and antibiotics for prevention of UTIs (prophylaxis), not treatment of active infections - antibiotics are definitely effective for treating UTIs, but low-dose preventative antibiotics aren’t that great for prevention and have the downside of potential resistance devlopment.
Ooookay! I think it get it. They’re equally effective for preventing them, but obviously antibiotics are used to treat, not prevent. That makes a ton of sense, thank you
No worries, I have to review a few meta -analysis a month. They are not all created equal. But some are trying to help.
