D-Mannose: A Sugar to Prevent Recurrent UTIs?

You know how cranberry juice remains one of the most popular home remedies for UTIs? Well, it turns out that the high D-mannose content in cranberry explains its efficacy for UTI symptoms. D-mannose, a simple sugar that’s related to glucose, is a valued anti-infective agent that is able to block bacteria from adhering to cells and flush them out of the body.

You don’t usually think of a simple sugar as a protective agent, right? But studies show that mannose has promising therapeutic value, especially for women dealing with recurrent urinary tract infections. Plus, the simple sugar boosts the growth of healthy bacteria in your gut and improves bladder health — all without negatively affecting your blood sugar levels.

What Is D-Mannose?

Mannose is a simple sugar, called a monosaccharide, that’s produced in the human body from glucose or converted into glucose when it’s consumed in fruits and vegetables. “D-mannose” is the term used when the sugar is packaged as a nutritional supplement. Some other names for mannose include D-manosa, carubinose and seminose.

Scientifically speaking, mannose is the 2-epimer of glucose. It occurs in microbes, plants and animals, and it is found naturally in many fruits, including apples, oranges and peaches. D-mannose is considered a prebiotic because consuming it stimulates the growth of good bacteria in your gut.

Structurally, D-mannose is similar to glucose, but it’s absorbed at a slower rate in the gastrointestinal tract. It has a lower glycemic index than glucose, as after it’s consumed it needs to be converted into fructose and then glucose, thereby reducing the insulin response and impact on your blood sugar levels.

Mannose is also filtered out of the body by the kidneys, unlike glucose that’s stored in the liver. It doesn’t stay in your body for long periods of time, so it doesn’t act as fuel for your body like glucose. This also means that mannose can positively benefit the bladder, urinary tract and gut without affecting other areas of the body.

UTI Prevention (and Other Uses and Benefits)

1. Treats and Prevents Urinary Tract Infections

D-mannose is thought to prevent certain bacteria from sticking to the walls of the urinary tract. Mannose receptors are part of the protective layer that’s found on cells that line the urinary tract. These receptors are able to bind to E. coli and washed away during urination, thereby preventing both adhesion to and invasion of urothelial cells.

In a 2014 study published in the World Journal of Urology, 308 women with a history of recurrent UTI, who had already received initial antibiotic treatment, were divided into three groups. The first group received two grams of D-mannose powder in 200 milliliters of water daily for six months. The second group received 50 milligrams of Nitrofurantoin (an antibiotic) daily, and the third group did not receive any additional treatment.

Overall, 98 patients had recurrent UTI. Of those women, 15 were in the D-mannose group, 21 were in the Nitrofurantoin group and 62 were in the no treatment group. Of the patients in the two active groups, both modalities were well-tolerated. In all, 17.9 percent of patients reported mild side effects, and patients in the D-mannose group had a significantly lower risk of side effects compared to patients in the Nitrofurantoin group.

Researchers concluded that D-mannose powder significantly reduced the risk of recurrent UTI and may be useful for UTI prevention, although more studies are needed to validate these results.

In a randomized cross-over trial published in the Journal of Clinical Urology, female patients with acute symptomatic UTIs, and with three or more recurrent UTIs in the preceding 12-month period, were randomly assigned to either an antibiotic treatment group (using trimethoprim/sulfamethoxazole) or to a regime including one gram of oral D-mannose three times daily for two weeks, following one gram twice daily for 22 weeks.

At the end of the trial period, the mean time UTI recurrence was 52.7 days with the antibiotic treatment group and 200 days with the D-mannose group. Plus, mean scores for bladder pain, urinary urgency and 24-hour voidings decreased significantly. Researchers concluded that mannose appeared to be safe and effective for treating recurrent UTIs and displayed a significant difference in the proportion of women remaining infection-free compared to those in the antibiotic group.

Why might mannose be such an effective agent for preventing recurrent UTIs? It really comes down to microbial resistance to traditional antibiotics. This is an increasing problem, with one study showing that more than 40 percent of 200 female college students with UTI symptoms were resistant to first-line antibiotics.

The study, published in Antimicrobial Agents and Chemotherapy, concludes with this warning: “Given the frequency with which UTIs are treated empirically, compounded with the speed that E. coli acquires resistance, prudent use of antimicrobial agents remains crucial.”

2. May Suppress Type 1 Diabetes

Researchers were surprised to find that D-mannose may be able to prevent and suppress type 1 diabetes, a condition in which the body doesn’t produce insulin — a hormone that’s needed to get glucose from the bloodstream into the body’s cells. When D-mannose was administered orally in drinking water to non-obese diabetic mice, researchers found that the simple sugar was able to block the progress of this autoimmune diabetes.

Because of these findings, the study published in Cell & Bioscience concludes by suggesting that D-mannose be considered a “healthy or good” monosaccharide that could serve as a safe dietary supplement for promoting immune tolerance and preventing diseases associated with autoimmunity.

3. Works as a Prebiotic

Mannose is known to act as a prebiotic that stimulates the growth of good bacteria in your gut. Prebiotics help feed the probiotics in your gut and amplify their health-promoting properties.

Research shows that mannose expresses both pro- and anti-inflammatory cytokines and has immunostimulating properties. When D-mannose was taken with probiotic preparations, combined they were able to restore the composition and numbers of indigenous microflora in mice.

4. Treats Carbohydrate-Deficient Glycoprotein Syndrome Type 1B

Evidence suggests that D-mannose is effective for treating a rare inherited disorder called carbohydrate-deficient glycoprotein syndrome (CDGS) type 1b. This disease makes you lose protein through your intestines.

It’s believed that supplementing with the simple sugar may improve symptoms of the disorder, including poor liver function, protein loss, low blood pressure and issues with proper blood clotting.

Risks and Side Effects

Because mannose occurs naturally in many foods, it’s considered safe when consumed in appropriate amounts. However, supplementing with D-mannose and taking doses higher than what would be consumed naturally may, in some cases, cause stomach bloating, loose stools and diarrhea. It’s also believed that consuming very high doses of D-mannose can cause kidney damage. According to researchers at the Stanford-Burnham Medical Research Institute in California, “mannose can be therapeutic, but indiscriminate use can have adverse effects.”

People with type 2 diabetes should use caution before using D-mannose products because they may alter blood sugar levels, though typically mannose itself doesn’t negatively impact blood sugar. To be safe, speak to your doctor prior to beginning any new health regime.

There’s not enough evidence to support the safety of mannose for women who are pregnant or breastfeeding. Based on the current research, there are no known drug interactions, but you should speak to your health care provider if you are taking any medications.

Top 20 D-Mannose Foods

D-mannose naturally occurs in a number of foods, especially fruits. Here are some of the top D-mannose foods that you can easily add to your diet:

1. Cranberries
2. Oranges
3. Apples
4. Peaches
5. Blueberries
6. Mangos
7. Gooseberries
8. Black currants
9. Red currants
10. Tomatoes
11. Seaweed
12. Aloe vera
13. Green beans
14. Eggplant
15. Broccoli
16. Cabbage
17. Fenugreek seeds
18. Kidney beans
19. Turnips
20. Cayenne pepper

Supplements and Dosage

It’s easy to find D-mannose supplements online and in some health food stores. They are available in capsule and powder forms. Each capsule is usually 500 milligrams, so you end up taking two to four capsules a day when treating a UTI. Powdered D-mannose is popular because you can control your dose, and it easily dissolves in water. With powders, read the label directions to determine how many teaspoons you need. It’s common for one teaspoon to provide two grams of D-mannose.

There is no standard D-mannose dosage, and the amount you should consume really depends on the condition you are trying to treat or prevent. There is evidence that taking two grams in powdered form, in 200 milliliters of water, every day for a six-month period is effective and safe for preventing recurrent urinary tract infections.

If you are treating an active urinary tract infection, the most commonly recommended dose is 1.5 grams twice daily for three days and then once daily for the next 10 days.

At this time, more research is needed to determine the optimal D-mannose dosage. For this reason, you should speak to your doctor before you begin using this simple sugar for the treatment of any health condition.

Final Thoughts

• D-mannose is a simple sugar that’s produced from glucose or converted into glucose when ingested.
• The sugar is found naturally in many fruits and vegetables, including apples, oranges, cranberries and tomatoes.
• The most well-researched benefit of D-mannose is its ability to fight and prevent recurrent UTIs. It works by preventing certain bacteria (including E. coli) from sticking to the walls of the urinary tract.
• Studies show that two grams of D-mannose daily is more effective than antibiotics for preventing recurrent urinary tract infections.

Read Next: Are You at Risk for Antibiotic Resistance?