D-mannose and diabetes: Uses, benefits, and risks

D-mannose is a natural sugar that scientists call a monosaccharide. It is present in several foods.

However, D-mannose is not the body’s primary energy source, with blood concentrations being less than one-fiftieth of those of glucose.

Therefore, when someone consumes D-mannose in foods, the body converts some of it to glucose to use as energy and combines some of it with proteins to form glycoproteins that have various functions, including playing a role in immunity.

The following foods naturally contain small quantities of D-mannose:

Additionally, one study reports that jujube fruit is a particularly rich source of D-mannose.

Retailers market D-mannose as a supplement to treat UTIs, for which many people consider it a routine remedy.

The primary use for D-mannose is to help treat UTIs, and this is where scientists have focused much of their research. However, there is some evidence that D-mannose may be beneficial for other conditions, too.

Urinary tract infections

The most widespread use for D-mannose is for UTIs. UTIs include cystitis, which causes urgency, pain, and discomfort when urinating.

Up to 90% of infections of the bladder are due to strains of Escherichia coli, which are present in fecal matter and can sometimes enter the urinary tract. Research suggests that D-mannose stops the bacteria from binding to cells and causing symptoms. A 2021 review concluded that D-mannose is protective for recurrent UTIs and may have similar effectiveness to antibiotics.

People with diabetes are more prone to developing UTIs, with one study finding that 8.2% of adults with diabetes in the United States had at least one UTI within the 1-year study period. Research indicates that this high prevalence is because people with diabetes have fewer antimicrobial proteins that protect the kidneys from fecal bacteria.

Another study suggested that UTIs can lead to worse outcomes in people with type 2 diabetes, as well as complications such as renal abscesses and bacteremia. This is because the infections are more resistant to treatments such as antibiotics.

Anti-inflammatory and immune regulating

Animal research has identified that D-mannose has anti-inflammatory properties in the intestine and may potentially treat conditions such as ulcerative colitis. However, scientists need to do more studies to examine its effects on humans.

Additionally, a 2017 study on mice showed that D-mannose might prevent autoimmune diabetes by regulating the immune system. However, evidence for the safe use of D-mannose for diabetes in humans is currently scarce.

Learn more about following an anti-inflammatory diet here.

D-mannose can combine with proteins in the body to form glycoproteins, which are present in cell membranes and other tissues. The way the body metabolizes glycoproteins can affect a person’s risk of developing diabetes.

A 2014 review notes that components of glycoproteins, such as D-mannose, may be a potential treatment for metabolic disorders. However, the authors state that there is insufficient research on D-mannose to recommend it safely for people with certain conditions, including diabetes, as it may lead to complications. In addition, they note that high D-mannose concentrations correlate with diabetes.

It is also important to note that D-mannose may cause side effects. One review indicated that 8% of people taking 2 grams of D-mannose for 6 months for a UTI experienced diarrhea.

Learn about home remedies for a UTI here.

Contact a doctor first

Due to how D-mannose affects blood sugar and the lack of conclusive evidence to confirm its safety, people with diabetes should not take it unless a doctor has recommended that they do so.

If someone with diabetes has a UTI, a doctor will usually prescribe antibiotics. If these are ineffective or the UTI is recurrent, the person should contact the doctor to discuss alternative treatments.

Cranberry juice as an alternative

Some people take cranberry juice to treat UTIs, but this may have adverse effects on blood sugar levels in people with diabetes. Therefore, these individuals should discuss treatment options with a healthcare professional before trying anything new.

Learn whether a person can treat a UTI without antibiotics here.

As D-mannose is a sugar, it can affect people with diabetes. The research on whether these effects are positive or negative is currently inconclusive.

D-mannose seems to be effective for treating recurrent UTIs, but if someone has diabetes, they should consult a doctor before using it. They should also ask the doctor about the suitability of other treatments for UTIs, which include antibiotics and cranberry juice.