I already know this article is about to break hearts and make enemies. I’m aware of the risks. After all, we’ve all grown up thinking it’s a miracle drug. Passed from mother to daughter in each generation, we’ve placed so much trust in cranberry juice. Cranberry juice is our one constant in the crazy, chaotic world of not peeing after sex. But it’s my job as a journalist (that’s a bit of a stretch) to break the news to you: there is no consistent, solid body of scientific evidence that says cranberry juice prevents or cures urinary tract infections. It goes against everything we’ve ever been told. I know, but call me the Gen Z Sheri Fink (that’s a somewhat niche New York Times health section reference… I guess if you have to explain the joke, it’s not that funny), I’m here to report on the facts and make scientific literature accessible to collegiate women. I’m sorry cranberry juice, but I’m about to end your whole career.
Okay, I was being dramatic, cranberry juice is not canceled. I’m a big fan of a vodka cran. Yet, as I said, the science is inconsistent. There’s little to no evidence that cranberry juice is curative for UTIs; antibiotics are often necessary unless you want a kidney infection. Additionally, cranberry’s ability to prevent infection is out for debate. There’s also not an agreement on how cranberries hypothetically prevent UTIs. We’re about to get science-y, but I’ll break it down for you. There’s a handful of hypotheses of how this works, one of which being that the compounds in cranberries act as antimicrobials and that’s generally agreed to not be accurate (1-7). However, a more recently published study in mice says that they did observe the acids in cranberry juice having antimicrobial properties (8). Biofilms are also thought to be involved in UTIs, especially recurring infections. A biofilm is a gooey matrix of cells (in this case, bacteria) that sticks to a variety of surfaces, from shower walls to the inside of your urinary tract. Biofilms can be difficult to get rid of and there is some evidence that the compounds in cranberry juice inhibit biofilm formation, but it depends on the bacteria you’re infected with (9-11). If cranberry juice does, in fact, reduce the risk of developing a UTI, the most probable hypothesis is that cranberry juice prevents bacteria from adhering to the walls of the urinary tract. This is what I grew up believing, but the evidence is inconsistent. Many studies (3, 5, 12-14) have found that cranberry inhibits the adhesion of multiple types of bacteria to a variety of surfaces in what is called a “dose-dependent fashion,” i.e. greater dosage of cranberry has a greater effect. However, none of these studies are in people; rather, these experiments were done in Petri dishes. It has been proposed that it may be unlikely in humans that some of the cranberry compounds preventing bacterial adhesion would be present in the urine at high enough concentrations to have an effect (15). Similarly, the hypothesis that cranberry juice increases the acidity of urine, thus increasing its antimicrobial properties, doesn’t hold up when you consider that the acidity levels aren’t clinically significant, i.e. though the acids may be present in the urine, it’s not at a high enough level to make a difference (1).
I know, I’m a mind reader. I know what you’re thinking. You’re thinking, “Summer! I am neither a mouse nor a petri dish!” I know that too; I would be impressed if a mouse was reading a Her Campus article. I’m glad we have that reach. I hope they’re following us on their minsta (mouse insta). Has science gone too far now that lab mice, trapped in their cages, have taken to reading an online collegiate women’s magazine? Were scientists so preoccupied with whether or not they could that they didn’t stop to think if they should? Are the mice running the lab now? All good questions, none of which are relevant to your urinary concerns.
As I said, I know you’re not a mouse and you’re definitely not a petri dish, so human clinical trials are important when talking about disease prevention. Sadly, I think we know where this is going: findings in clinical trials regarding cranberries and UTIs are variable. Cranberries have been shown to both prevent (16,17) and not prevent (18,19) UTIs in clinical trials, and meta-analyses of RCTs (randomized controlled trials) are weird, to say the least. A meta-analysis uses statistical methods to combine findings from several studies and, like any analysis, they have strengths and weaknesses. The quality of a meta-analysis can come down to the designs and quality of each study in the analysis. Unfortunately, some of these meta-analyses reporting a preventative relationship of cranberries with UTIs have strong limitations due to large differences in design among the studies (which makes them hard to compare), poor study design, and high study participant drop-out rates (1,20,21). One of these meta-analyses even says, “consumption of cranberry-containing products may protect against UTIs in certain populations. However, because of the substantial heterogeneity across trials, this conclusion should be interpreted with great caution” (21). Frankly, I want that last part on a shirt; it’s a fancy way of saying “there’s a good chance I’m wrong.”
There are several ways to prevent UTIs that don’t involve cranberries:
1. (cue TikTok harp music) you have to start peeing after sex. Don’t ask me why, you know why. Think about it. Do you think Ben from that sticky frat washes his hands? Do you know the last time Veronica scrubbed under their fingernails? Are you taking a sanitation break? And still, regardless of cleanliness, any bacteria in the vagina, whether it be naturally or introduced, will likely travel to the urethra during sex simply based on proximity. Peeing after sex flushes out that bacteria.
2. Healthy bowel behavior is helpful in that any fecal bacteria that relocates to the urethra can cause infection; thus, having regular, healthy, solid bowel movements reduces the risk of that happening.
3. Take probiotics as an extra step of precaution for preventing UTIs promote the growth of healthy bacteria rather than unhealthy bacteria (talk to your doctor first!)
In all, there are two things I want you to take away from this. One, please don’t think that this is a comprehensive literature review. That would take months instead of hours to write. Using cranberry juice as UTI prevention has been a heavily researched topic for the last century; there’s no way one Her Campus article is going to encapsulate every scientific finding ever. Two, until there’s general scientific agreement that cranberries prevent UTIs, I personally wouldn’t keep buying cranberry supplements thinking that it’s doing anything. As of right now, you probably are just paying for expensive pee. However, it likely won’t hurt you, so go for it, I guess, if you want to spend that money. Keep drinking cranberry juice, though, not for urinary tract health, but because we need to keep Ocean Spray in business. Like I said, I love a vodka cran.
- Guay, D.R. (2009). Cranberry and Urinary Tract Infections. Drugs, 69, 775-807.
- Gupta, K., Chou, M.Y., Howell, A., et al. (2007). Cranberry products inhibit adherence of p-fimbriated Escherichia coli to primary cultured bladder and vaginal epithelial cells. Journal of Urology, 177, 2357-2360.
- Sobota, A.E. (1984). Inhibition of bacterial adherence by cranberry juice: potential use for the treatment of urinary tract infections. Journal of Urology, 131, 1013-1016.
- Ahuja, S., Kaack, B., Roberts, J. (1998). Loss of fimbrial adhesion with the addition of Vaccinium macrocarpon to the growth medium of P-fimbriated Escherichia coli. Journal of Urology, 159, 559-562.
- Valentova, K., Stejskal, D., Bednar P., et al. (2007). Biosafety, anti-oxidant status, and metabolites in urine after consumption of dried cranberry juice in healthy women: a pilot double-blind placebo-controlled trial. Journal of Agricultural and Food Chemistry, 55, 3217-3224.
- Lee, Y-L., Owens, J., Thrupp, L., et al. (2000). Does cranberry juice have any antibacterial activity? [letter]. Journal of the American Medical Association, 283, 1691.
- Allison, D.G., Cronin, M.A., Hawker, J., et al. (2000). Influence of cranberry juice on attachment of Escherichia coli to glass. Journal of Basic Microbiology, 40, 3-6.
- Jensen, H.D., Struve, C., Christensen, S.B., et al. (2017). Cranberry juice and combinations of its organic acids are effective against experimental urinary track infection. Frontiers of Microbiology, 8, 542.
- Di Martino, P., Agniel, R., Gaillard, J.L., et al. (2005). Effects of cranberry juice on uropathogenic Escherichia coli in vitro biofilm formation. Journal of Chemotherapy, 17, 563-565.
- Reid, G., Hsiehl, J., Potter, P., et al. (2001). Cranberry juice consumption may reduce biofilms on uroepithelial cells: pilot study in spinal cord injured patients. Spinal Cord, 39, 26-30.
- Morris, N.S., Strickler, D.J. (2001). Does drinking cranberry juice produce urine inhibitory to the development of crystalline, catheter-blocking Proteus mirabilis biofilms? BJU International, 88, 192-197.
- Zafriri, D., Ofek, I., Adar, R., et al. (1989). Inhibitory activity of cranberry juice on adherence of type 1 and type P fimbriated Escherichia coli to eukaryotic cells. Antimicrobial Agents and Chemotherapy, 33, 92-98.
- Schmidt, D.R., Sobota, A.E. (1988). An examination on the anti-adherence activity of cranberry juice on urinary and nonurinary bacteria isolates. Microbios, 55, 173-181.
- Eydelnant, I.A., Tufenkji, N. (2008). Cranberry derived proanthocyanidins reduce bacterial adhesion to selected biomate-rials. Langmuir, 24, 10273-10281.
- Dearing, M.D., Appel, H.M., Schultz, J.C. (2002). Why do cranberries reduce incidence of urinary tract infections? [letter]. Journal of Ethnopharmacology, 80, 211.
- Foxman, B., Cronenwett, A.E.W., Spino, C., et al. (2015). Cranberry juice capsules and urinary tract infection post surgery: results of a randomized trial. American Journal of Obstetrics and Gynecology, 213 (2), 194-198.
- Kontiokari, T., Sundqvist, K., Nuutinen, M., et al. (2001). Randomised trial of cranberry-lingonberry juice and Lactobacillus GG drink for the prevention of urinary tract infections in women. British Medical Journal, 322(7302), 1571.
- Stapleton, A.E., Dziura, J., Hooton, T.M., et al. (2012). Recurrent urinary tract infection and urinary Escherichia coli in women ingesting cranberry juice daily: a randomized controlled trial. Mayo Clinic Proceedings, 87(2), 143-150.
- Barbosa-Cesnik, C., Brown, M.B., Buxton, M., et al. (2011). Cranberry juice fails to prevent recurrent urinary tract infection: results from a randomized placebo-controlled trial. Clinical Infectious Diseases, 52(1), 23-30.
- Fu, Z., Liska, D., Talan, D., et al. (2017). Cranberry reduces the risk of urinary tract infection recurrence in otherwise healthy women: a systematic review and meta-analysis. The Journal of Nutrition, 147(12), 2282-2288.
- Wang, C.H., Fang, C.C., Chen, N.C. (2012). Cranberry-containing products for prevention of urinary tract infections in susceptible populations: a systematic review and meta-analysis of randomized controlled trials. Archives of Internal Medicine, 172(13), 988-996.