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Mannose: This Sugar Has Incredible Benefits

Written by Dr. Joseph Mercola Fact Checked

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Story at-a-glance -

  • Mannose, a simple sugar found in cranberries and other fruits and vegetables, has been shown to reduce the size of cancerous tumors in lab mice
  • Not only was mannose shown to interfere with the ability of cancerous tumors to take up glucose, it also boosted the effectiveness of certain chemotherapy drugs
  • Specifically, mannose slowed the growth of tumors associated with lung, pancreatic and skin cancers
  • In supplement form, mannose is commonly used to treat urinary tract infections (UTIs) and bladder inflammation
  • High concentrations of mannan saccharides are available in the gel of aloe plants, contributing to aloe’s anti-inflammatory and wound-healing effects

Normally, sugar and cancer go together in a negative way. Because a growing number of studies show sugar feeds cancer1,2,3,4 and plays a role in most chronic disease,5 I typically advise you eliminate refined sugar from your diet. I also recommend you limit your fructose consumption for similar reasons. Even when consumed in the form of whole fruit, fructose may be harmful to your health if eaten excessively.

Now, research out of Scotland suggests a type of sugar called mannose, found in cranberries and other fruits, may be useful in the treatment of certain cancers. In experiments involving lab mice, mannose was shown to interfere with the ability of cancerous tumors to take up glucose. It also boosted the effectiveness of chemotherapy drugs.

Mannose Shown to Suppress Cancer in Lab Mice

While sugar has been shown to fuel cancer growth, a team of European researchers, most of whom represent the Cancer Research UK Beatson Institute for Cancer Research at Scotland’s University of Glasgow, have found quite the opposite.

In experiments involving lab mice, Kevin Ryan, Ph.D., professor of molecular cell biology at the University of Glasgow, and his colleagues found mannose:6,7,8

  • Slowed the growth of multiple cancers, including lung, pancreatic and skin, presumably by interfering with the ability of cancerous tumors to take up glucose
  • Reduced the size of cancerous tumors
  • Boosted the effectiveness of cancer drugs — specifically cisplatin and doxorubicin, two of the most widely used chemotherapy medications
  • Did not affect the weight or health of the mice

Mannose also increased the life span of some of the mice. The results of their research were published in the November 2018 issue of the journal Nature.9 To date, mannose has been used as a natural treatment for cystitis (inflammation of the bladder) and urinary tract infections (UTIs).

After Ryan and his team added mannose to the drinking water of mice suffering from lung, pancreatic or skin cancer, they noticed tumor growth slowed. In addition, they noted no obvious side effects to the mice treated with mannose.

“Tumors need a lot of glucose to grow, so limiting the amount they can use should slow cancer progression,” said Ryan. “The problem is that normal tissues need glucose, as well, so we can’t completely remove it from the body.”10

As such, the researchers had to find a dose of mannose sufficient to block glucose such that it slowed tumor growth, but allowed normal tissues to remain unaffected. “This is early research, but it is hoped that finding this perfect balance means that, in the future, mannose could be given to cancer patients to enhance chemotherapy without damaging their overall health,” Ryan stated.11

Beyond the cancers mentioned above, the team exposed cells from other types of cancer — including bone, bowel, leukemia and ovarian — to mannose. Some of the cancer cells responded well to mannose while others did not. About this, one source noted, “The anticancer potential of mannose appeared to depend on whether an enzyme that breaks down the sugar was present in cells.”12

Should You Use Cranberry Juice to Treat UTIs or Cancer?

Very likely you’ve been told that drinking cranberry juice can soothe cystitis and UTIs. Now, the current research seems to suggest it can be used to treat cancer. As such, you may be thinking about loading up on cranberry juice, which I do not recommend.

First, while the use of mannose to treat bladder and urinary tract issues is well founded, I advise you to avoid cranberry juice as a medical treatment. That’s because you’d have to drink a lot of juice, which is often laden with toxic amounts of sugar.

For those conditions, consult your medical practitioner to ensure an accurate diagnosis and then inquire about the possible use of a mannose-containing supplement. Second, with respect to cancer treatment and mannose, keep in mind this research is preliminary and has yet to be tested on humans.

With respect to that, Ryan commented, “Our next step is investigating why [the] treatment only works in some cells, so that we can [determine] which patients might benefit the most from this approach.” He expressed his desire to see clinical trials begin on mannose “as soon as possible to determine its true potential as a new cancer therapy.”

Martin Ledwick, Cancer Research UK’s head information nurse, joined Ryan in cautioning cancer patients to resist the temptation to self-medicate with mannose. Ledwick said:

“Although these results are very promising for the future of some cancer treatments, this is very early research and has not yet been tested in humans.

Patients should not self-prescribe mannose as there is a real risk of negative side effects that haven’t been tested for yet. It’s important to consult with a doctor before drastically changing your diet or taking new supplements.”

The bottom line is it’s difficult to regulate your body’s glucose levels in a healthy manner through self-experimentation. This is particularly the case if you are dealing with a serious illness like cancer or diabetes. While mannose may be a useful complementary treatment, I also encourage you to:

  • Eat a healthy, whole food diet, which implies avoiding processed foods and sugar, especially soda and sweets
  • Exercise regularly
  • Get at least seven to nine hours of high-quality sleep every night
  • Reach out for or continue receiving treatment from professional health care practitioners who are familiar with your condition and experienced in natural approaches

What Is Mannose and How Does It Work?

As mentioned, mannose is a monosaccharide found in cranberries and other fruits, including apples, blueberries, oranges and peaches. It also resides in vegetables like broccoli, cabbage and green beans.

About this simple sugar, The Clinical Advisor says, “In addition, d-mannose occurs naturally in some cells in the human body and is thought to be a prebiotic, because consumption of d-mannose stimulates and fosters the growth of good bacteria in the digestive tract.”

Beyond its presence in whole foods and your body, mannose also commonly appears in supplement form under the name D-mannose. Although mannose is chemically considered a simple sugar, structurally, it is similar to glucose.

That said, it is absorbed more slowly in your gastrointestinal tract than glucose, which accounts for its lower glycemic index. With respect to this aspect of mannose, The Clinical Advisor notes:

“Compared with actual glucose, which is readily absorbed and has a glycemic index of 100, mannose must first be converted into fructose and then into glucose, significantly blunting the insulin response and reducing its impact on blood sugar levels.

After mannose is absorbed by the gut, it is not stored in the liver like glucose, but is filtered out of the body directly by the kidneys.”

For the experiments in which mannose was given to lab mice afflicted by cancers such as bone, bowel, leukemia and ovarian, mannose was shown to more readily disrupt cells that had lower levels of an enzyme called phosphomannose isomerase (PMI). About the impact of PMI, the study authors stated:

“Cells with low levels of PMI are sensitive to mannose, whereas cells with high levels are resistant. … PMI levels also vary greatly between different patients and different tumor types, indicating that PMI levels could be used as a biomarker to direct the successful administration of mannose. …

[T]he administration of mannose could be a simple, safe and selective therapy in the treatment of cancer, and could be applicable to multiple tumor types.”

Research Validates Mannose for Treating Rare Disease CDG and UTIs

D-mannose has been shown to help in the treatment of a rare disease called carbohydrate-deficient glycoprotein syndrome type 1b (CDG 1b). This condition is passed down through families and is characterized by liver and digestive problems associated with hyperinsulinism and inconstant thrombosis. Beyond that, the condition causes your body’s blood coagulation factors to be decreased.

About CDG 1b and mannose, authors of a 2009 study commented, “In our experience, mannose given orally at least four times per day not only transformed lethal CDG 1b into a treatable disease, but also improved the general condition and digestive symptoms of all reported patients but one.”17

As mentioned, D-mannose is commonly used to prevent and treat UTIs, which are usually caused when E. coli bacteria is transferred from your intestinal tract to your urinary tract. D-mannose is great for UTIs because it attaches to the E. coli bacteria, causing them to stick to each other instead of clinging to the walls of your urinary tract.

Under those conditions, the harmful bacteria can be eliminated from your body during urination. Given the increasing instances of antibiotic resistance, natural remedies for UTIs are imperative.

A 2014 study published in the journal World Journal of Urology found D-mannose powder to be as effective as an antibiotic in treating recurrent UTIs in women. A total of 308 women were divided into three groups:18

  • The first group received 2 grams (g) of D-mannose powder mixed in water daily for six months
  • A second group was given 50 milligrams (mg) of the antibiotic Nitrofurantoin daily
  • The third group was a control group and received no treatment

Of the 98 patients experiencing a recurrent UTI, just 15 percent of them consumed D-mannose, whereas 20 percent took the antibiotic and 61 percent received no treatment.

With respect to the outcomes, the study authors said, “D-mannose powder significantly reduced the risk of recurrent UTI, which was no different from [the] Nitrofurantoin group. More studies will be needed to validate the results … but initial findings show that D-mannose may be useful for UTI prevention.”19

If you have been plagued by recurrent UTIs or bladder inflammation, particularly if you are concerned about antibiotic resistance, now may be the time to talk to your health care practitioner about trying D-mannose. It is generally quite effective for up to 90 percent of UTI cases.

The only exception would be UTIs caused by a bacterium other than E. coli; in that case, you’d be better served to ask your doctor about supplements known to disrupt biofilms.20

Mannose Contributes to the Healing Properties of Aloe Vera

While you probably know aloe vera is beneficial for soothing burns, improving wound healing and inhibiting inflammation, you may not be aware that the major sugar in aloe vera is mannose. In a 1994 study, lab mice receiving 300 mg/kilogram (kg) of mannose-6-phosphate showed improved wound healing compared to those treated with saline controls.

The researchers noted, “This dose also had anti-inflammatory activity.”1` Authors of a 2004 study added, “The clear pulp, also known as inner gel, of [the] Aloe vera L. leaf is widely used in various medical, cosmetic and nutraceutical applications. Many beneficial effects of this plant have been attributed to the polysaccharides present in the pulp.”22

Another source states, “High concentrations of mannan saccharides are available in the gel of aloe plants. Laboratory studies show the effects of glucomannan saccharides signals as they activate the immune response through increased expressions of interleukin-1, interleukin-6 and tumor necrosis factor.”

Cautions About Taking Mannose

While mannose is thought to be well tolerated in most people, I do not recommend supplementing with it if you are pregnant or breastfeeding due to the lack of research validating its safe use. That said, pregnant and breastfeeding moms should be fine consuming mannose-containing foods, assuming it is done in moderation. 

The side effects associated with mannose may include bloating and loose stools. Beyond that, since mannose could make it harder to regulate your blood sugar if you have diabetes, use caution when taking D-mannose supplements if you are diabetic.

While the news about mannose as a potential cancer fighter is encouraging, more research, including clinical trials, is needed to validate its effectiveness. For your safety, always consult a medical professional before taking a new supplement or changing the dosing associated with any of your existing supplements.