Can Taking D-Mannose Prevent a UTI (Urinary Tract Infection)?

If you've ever had a UTI (urinary tract infection) or bladder infection, you know how uncomfortable it can be, which is why some people turn to natural strategies. One remedy typically touted for UTI prevention is D-mannose, a type of sugar found in a number of fruits (including cranberries, black and red currants, and peaches) and also available in dietary supplement form.

D-mannose is thought to keep bacteria from sticking to the walls of the urinary tract, which is why it's sometimes taken as a home remedy to prevent recurrent UTIs.

Related: Natural Remedies for UTIs

While there's a lack of high-quality clinical trials (the kind of research you want to see to put stock in a treatment) showing that D-mannose can be helpful for UTIs, preliminary studies suggest that the supplement could be worth exploring.

In a laboratory study published in the journal PLoS One in 2008, for instance, scientists demonstrated that D-mannose can help stop E. coli (the type of bacteria responsible for the vast majority of UTIs) from sticking to cells found in the urinary tract.

For a study published in World Journal of Urology in 2014, researchers examined the use of D-mannose (in addition to antibiotic treatment) in 308 women with an acute UTI and a history of recurrent UTIs. After one week of treatment with antibiotics, participants took D-mannose powder, the antibiotic nitrofurantoin, or nothing for six months for prevention.

During the six-month period, the rate of recurrent UTIs was significantly higher in women who took nothing compared to those who took D-mannose or nitrofurantoin. The main side effect noted was diarrhea, which occurred in 8 percent of women taking D-mannose.

A small pilot study in European Review for Medical and Pharmacological Sciences found that D-mannose administered twice daily for three days followed by once a day for ten days resulted in a significant improvement in symptoms, UTI resolution, and quality of life. Those who received D-mannose for six months following treatment had a lower rate of recurrence than those who took nothing.

Despite these studies, in a review of previously published studies (published in the International Urogynecology Journal), researchers reviewed non-antibiotic prevention strategies such as cranberry, vitamin C, and D-mannose and concluded that these strategies "lack strong evidence to be introduced as routine management options and as alternatives to antibiotics".

Little is known about the safety of long-term or high-dose use of D-mannose supplements. However, D-mannose supplements can trigger a number of side effects such as bloating, loose stools, and diarrhea. When taken in excessive doses, there's some concern that D-mannose may lead to kidney damage.

Since D-mannose may alter your blood sugar levels, it's crucial for people with diabetes to take caution when using D-mannose supplements. Not enough is known about the safety of the supplement during pregnancy or breastfeeding, so it should be avoided. Children shouldn't take D-mannose.

It's also worth noting that self-treating any condition with D-mannose supplements, and avoiding or delaying standard care, may have serious health consequences.

UTIs can be a recurring problem and can be tough to treat. While it may be tempting to try D-mannose to self-treat a UTI, if the infection isn't completely eradicated, it may spread (to the kidneys) even if the symptoms are gone. Also, there are some concerns about the side effects that may result from taking high doses of the supplement.

If you're still thinking of trying it (or are considering taking it for preventative purposes), be sure to talk with your doctor first to weigh the pros and cons and discuss whether it's the best option for you.

Some people opt for cranberry juice, which contains other compounds besides D-mannose (including proanthocyanins, a type of antioxidant) that may help keep bacteria from adhering to the walls of the urinary tract. A research review, however, found that the benefit for preventing UTIs is small.

For more help in fighting off urinary tract infections, make sure to drink plenty of water on a regular basis and avoid holding your urine for extended periods of time. You'll increase the likelihood that bacteria will be flushed from your urinary tract before infection sets in.