D-mannose: benefits, side effects, dosages and interactions


D-mannose (or mannose) is a type of sugar found in many fruits and vegetables, including blueberries , black and red currants, peaches, green beans, cabbage, and tomatoes. It is also made in the body from glucose, another form of sugar.

As a dietary supplement, D-mannose is often touted as a natural way to treat and prevent urinary tract infections (UTIs) or bladder infections (cystitis). While more research is needed, preliminary research suggests this supplement is worth investigating.

Since frequent urinary tract infections are treated with long-term low-dose antibiotics (six months or more), Treating this type of infection without the use of antibiotics , representing more than six million visits to healthcare providers a year, would help prevent antibiotic resistance.

Get Medical Information / Jessica Olah

Health benefits

Several small studies have shown that D-mannose can prevent bacteria from attaching to the cells that line the urinary tract. A study published in 2008 in the journal PLoS One showed that D-mannose can help prevent Escherichia coli (the bacteria responsible for the vast majority of UTIs) from attaching to cells in the urinary tract .

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

Over a six-month period, the recurrence rate for UTIs was significantly higher in women who took nothing compared to those who took D-mannose or nitrofurantoin. Fewer side effects have been reported with D-mannose than with antibiotics. The main one was diarrhea, which was seen in 8% of the women taking D-mannose.

A small pilot study of 43 women, published in 2016, found that giving D-mannose twice daily for three days and then once daily for 10 days resulted in significant improvement in symptoms, resolution of urinary tract infections, and quality of life. Those who received D-mannose for six months after treatment had a lower relapse rate than those who took nothing .

While D-mannose is promising, a review of studies published in 2015 concluded that D-mannose (and other non-pharmaceuticals such as cranberry juice and vitamin C) are poor candidates to replace antibiotics in the treatment of urinary infections

Possible side effects.

Common side effects of D-mannose include bloating, loose stools, and diarrhea. Since D-mannose is excreted in the urine, there is also a concern that high doses could damage the kidneys.

Because D-mannose can alter blood sugar levels, it is imperative that people with diabetes exercise caution when using D-mannose supplements. Not enough is known about the safety of the supplement during pregnancy or breastfeeding and it should be avoided. Children should also not take D-mannose.

In general, self-treatment of a UTI with D-mannose or avoiding or delaying standard treatment is not recommended as it can lead to serious complications, including a kidney infection ( pyelonephritis ) and even irreversible kidney damage.

Dosage and preparation

Little is known about the long-term safety of D-mannose or how much the supplement can be considered harmful or toxic at what doses. But studies have also used doses of up to two grams per day to prevent UTIs and three grams to treat UTIs .

Although D-mannose is generally considered safe because it occurs naturally in many foods, doses higher than those consumed in a normal diet can create unknown health problems; at this stage it is simply not known.

What to look for

It is important to remember that nutritional supplements have not been tested for safety and are largely unregulated. When shopping for nutritional supplements, look for products that are certified by ConsumerLabs, USP, or NSF International. These organizations do not guarantee that the product is safe or effective, but indicate that it has been tested for quality.

Get the word of drug information

If you're still thinking about trying D-mannose for UTIs (or considering it as a preventative measure), first speak with your doctor to weigh the pros and cons and decide if this is the best option for you.

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