D-Mannose: Benefits and Side Effects

Mary Lucas, RN

Medically reviewed by Mary Lucas, RN

Written by Our Editorial Team

Last updated 2/14/2021

D-mannose, also known as carubinose, D-manosa, seminose or simply mannose, is a naturally occurring sugar. 

You can find high amounts in fruits like cranberries, apples, oranges, peaches and blueberries.This sugar is also found in some cells in the human body and can also be produced from fructose and glucose. 

Now, while trivia on this simple sugar's alternate names and sources may get you plenty of attention at the dinner table, a mention of its potential in treating a rare disease called carbohydrate-deficient glycoprotein syndrome type 1b is more likely to impress. 

But if you really want to get everyone talking, bring up the suspected benefits of D-mannose in treating urinary tract infections (UTIs).

We’ll be checking out the health benefits of D-mannose. However, we’ll be paying extra attention to its potential advantages for urinary tract infections. 

We’ll also examine the risks of this sugar and any precautions to be observed when making use of it.

Health Benefits of D-Mannose

Before we zero in on any benefits of D-mannose for carbohydrate-deficient glycoprotein syndrome and UTIs, there are two other potential uses of this sugar we should mention: obesity prevention and prebiotic functions.

Now, don't get too excited because most of the research has been on animals — but there is a chance that supplementing a high-fat diet with mannose early in life could prevent adverse outcomes. 

This could be due to the fact that this sugar is an inefficient energy source, leaving gut microbiota with a potential lower energy harvest. Your body’s energy absorption may also be reduced as a result.  

As mentioned, please be aware that this has not been shown to be true in humans and the only testing done has been on mice.

Mannose could also hold benefits for promoting healthy gut bacteria. It may perform prebiotic functions by binding to harmful bacteria in the gut. However, more research is needed to determine its effects on humans.

That said, let’s hone in on the potential benefits of D-mannose in treating the genetic condition: carbohydrate-deficient glycoprotein syndrome. 

Carbohydrate-Deficient gGlycoprotein Syndrome 1B

Congenital disorders of glycosylation (CDG) or carbohydrate-deficient glycoprotein syndromes are genetic conditions that affect a process called glycosylation. 

A little more dinner table material — glycosylation is the complex process where carbohydrates attach to a protein (called glycoproteins) or another organic molecule. (build long sugar chains that are attached to proteins called glycoproteins). The formation process of these glycoproteins is pretty intricate, with each step requiring a particular enzyme.

While 19 types of CDGs have been identified, there are four main categories under which there are different types. Each type is determined by a particular enzyme missing for the glycosylation process. 

In carbohydrate-deficient glycoprotein syndrome type 1b, the glycosylation  process is missing an enzyme called phosphomannose isomerase (PMI).  This enzyme is required for mannose metabolism. 

The symptoms of this condition include clotting issues, bleeding and diseases of the stomach and intestine.

There is evidence that D-mannose may help in treating this condition. By ingesting supplements of this sugar,  blood mannose levels may  be increased in the body. 

It may also remedy some of the symptoms of underglycosylation noticed in patients. Ingested D-mannose can  cause an increase in blood mannose levels for normal patients and people experiencing this condition.

While more research is needed to confirm these benefits — the case of a child whose symptoms of PMI deficiency were managed by improving his mannose levels, shows some evidence of this simple sugar's advantages in the management of CDGS.

In this case, the child began showing symptoms of the condition early, with bouts of diarrhea and vomiting at around 11 months. His symptoms of PMI deficiency didn't improve after that. 

In later years, he would deal with dangerous conditions of the intestine that caused protein loss. He also experienced blood clots  in both legs, as well as  repeated severe gastrointestinal bleeding that could not be managed with surgery or medications and therefore threatened his life.

Ingestion of oral mannose supplements improved his condition and the  symptoms of his defect were resolved.

But, we’ll repeat, this is just one case study and more research is needed to assess and determine  the impact D-mannose can have in treating genetic carbohydrate-deficient glycoprotein syndrome 1b.

What Is a Urinary Tract Infection?

It doesn't matter how common UTIs are (1 in 3 women are likely to have experienced a UTI by age 24), having an urgent need to pee, only to have a little come out, or feeling a stinging sensation when relieving yourself, will always feel more than a little uncomfortable.

A UTI is an infection in the urinary system  which is usually caused by bacteria. Other causes may be fungal or viral.

There are several types of UTIs, where the infection occurs typically determines what kind of infection it is: urethritis affects the urethra, cystitis is an infection of the bladder, and pyelonephritis is an infection of  the kidneys. 

In addition to painful urination and an urge to pee with little results, other not so great symptoms of a UTI include milky, cloudy or foul-smelling urine, as well as pain in the back or lower stomach.

For years, cranberry juice has been anecdotally recommended and consumed by many as a way  to help with the prevention and treatment of UTIs. Likewise, antibiotics have been considered  the go-to medication for managing symptoms.

However, while cranberry juice can quench your thirst on a hot, sunny day, it may not be as effective in preventing or treating cases of urinary tract infections. There are conflicting reports  on its benefits in managing UTIs when used alone, even though it contains high amounts of D-mannose. 

Likewise, despite antibiotics being a proven treatment for UTIs, your body may develop a resistance to specific antibiotics when antibiotic-resistant strains emerge.

Based on the above, we could argue that there is a  need for alternate means of managing urinary tract infections. Luckily, a new player  may be emerging. Despite its full potential still in the early stages of research, there is some promise of D-mannose being an effective way of preventing and treating urinary tract infections.

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How Does D-Mannose Help in Preventing and Treating UTIs?

Remember how we said UTIs are usually caused by bacteria? These  bacteria typically operate by sticking to the walls of the urinary tract where they  cause infections.

D-mannose may be able to prevent this by giving the bacteria a super tight bear hug — or binding to the bacteria, if you want to get technical. 

Binding to the bacteria prevents them from sticking to the walls of the urinary tract and causing infections.

Because D-mannose is very quickly absorbed and excreted by the urinary tract, it can take this bacteria down with it when it exits the body in urine. This process may be effective in treating and preventing cases of urinary tract infections.

In a study carried out for a little over a year, D-mannose was administered twice daily for three days, and then once a day for 10 days to patients with UTIs.  

They were then randomised to either continue receiving D-mannose as a preventative for 6 months or to not receive it. 

At the end of the study, D-mannose was shown to have positive effects in resolving and preventing UTIs.

In another study, mannose was shown to have the potential to not only prevent bacteria from sticking to the urinary walls, but also in preventing their invasion into the cells. This could be a positive sign that mannose can also hold off UTIs.

But that’s not all — D-mannose may be just as effective for treating UTIs as other established remedies. In a study where 308 women first received antibiotic treatments for their recurrent UTIs, mannose was shown to be as effective as the antibiotic — nitrofurantoin — in reducing the risk of recurrent UTIs, a tiring issue when it comes to treating UTIs. This sugar was also shown to have fewer  side-effects.

While D-mannose is yet to receive approval for the treatment and prevention of UTIs, there is mounting evidence of   its usefulness in promoting urinary health and wellness.

Risk Factors of D-Mannose

Because more research is required to determine the effects and side-effects of D-mannose, you have to be a little careful when trying it out.

Special classes of people like pregnant or lactating mothers should avoid using D-mannose altogether for  treating UTIs or other conditions because we simply don't know enough about its impact in pregnancy, most studies have been conducted on non-pregnant females.

Likewise, because mannose is a sugar, there is a chance that consuming it can lead to increased sugar levels, an effect that can prove dangerous if you live with diabetes. 

Therefore , it wouldn't hurt to exercise care when using this sugar. Other known side-effects include diarrhea.

D-Mannose For Urinary Tract Health

D-mannose is a simple sugar with a potential for not-so-simple benefits on our health and wellness.

In particular, this sugar may hold real promise in promoting improved wellness for your urinary tract, a benefit which is always welcome.

To make sure your urinary tract is always on the right track to health and wellness, our D-mannose powder, containing the combined goodness of antioxidants, electrolytes, and ofcourse mannose, is all set and ready to help.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.