Can D-Mannose Prevent a Urinary Tract Infection?

Evidence remains split on the potential benefits

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

A number of smaller studies have suggested that D-mannose may hinder bacteria from adhering to the cells lining the urinary tract. Research published in 2008 in the journal PLoS One demonstrated that D-mannose can help stop E. coli (the bacteria responsible for the vast majority of UTIs) from sticking to cells in the urinary tract.

Potential Benefits

While there's a lack of high-quality clinical trials investigating D-mannose's efficacy in treating UTIs, preliminary studies suggest that the supplement could be well worth exploring.

A study published in the World Journal of Urology in 2014 examined the use of D-mannose to prevent recurrent urinary tract infections. After one week of initial treatment with antibiotics for an acute UTI, 308 women with a history of recurrent UTIs took D-mannose powder, the antibiotic nitrofurantoin, or nothing for six months.

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 10 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.

Although D-mannose shows promise, a review of studies published in 2015 concluded that D-mannose (and other non-pharmaceutical remedies like cranberry juice and vitamin C) are ill-suited to replace antibiotics in treating UTIs.

Side Effects

Little is known about the long-term safety of D-mannose or at what dose the supplement may be considered harmful or toxic.

While D-mannose is typically considered safe because it occurs naturally in many foods, doses higher than what is consumed through normal diets may pose unknown health problems; we simply don't know at this stage.

Common side effects of D-mannose include bloating, loose stools, and diarrhea. As D-mannose is excreted from the body in urine, there is also some concern that high doses may injure or impair the kidneys.

Since D-mannose can 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 as well.

A Word From Verywell

If you get recurrent UTIs, you may be looking for additional ways to prevent them. While there is some research suggesting that D-mannose may help, there is nothing to suggest that it is or will ever be considered a substitute for antibiotics.

As a rule, self-treating a UTI with D-mannose, or avoiding or delaying standard care, is unadvised as it can lead to serios complications, including a kidney infection (pyelonephritis) and even permanent kidney damage.

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

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