- Glucomannan benefits and side effects
- Side Effects
- The Fiber Supplement for Weight Loss That Dr. Oz Loves
- Glucomannan: Benefits, Side-effects, Dosage
- What is glucomannan and what does it do?
- What does glucomannan do in the body?
- How much glucomannan is safe to take?
- What are the side-effects of taking glucomannan?
- 15 Glucomannan Health Benefits, Risks & Side Effects
- What Is Glucomannan?
- Mechanisms of Action
- Potential Benefits of Glucomannan
- 1) Cholesterol
- 2) Diabetes
- 3) Constipation
- Insufficient Evidence For
- 4) Weight Management
- 5) Gut Health
- 6) Polycystic Ovary Syndrome
- 7) Hyperthyroidism
- 8) Skin Damage
- Animal & Cell Studies (Lacking Evidence)
- 9) Acne
- 10) Inflammation
- 11) Allergies
- 12) Antioxidant Activity
- 13) Aging
- Side Effects & Precautions
- User Reviews
- All About Glucomannan
- What are soluble fibers?
- From konjac root to glucomannan
- What does glucomannan do?
- Absorbs water
- Helps us feel fuller, longer
- Better carbohydrate tolerance & lipid profile
- GI health
- Glucomannan safety
- Start slowly
- How to take glucomannan
- Summary & recommendations
- Learn more
- Safety and Efficacy of Glucomannan for Weight Loss in Overweight and Moderately Obese Adults
Glucomannan benefits and side effects
Glucomannan is a natural fiber supplement derived from yams that helps dieters lose weight.
Packing around more pounds than we need or is a common problem; many people want to be thinner and also enjoy the health benefits of maintaining normal weight.
If you’re one of the 45 million Americans who buy weight-loss products, spending a total of $33 billion each year (1), you may want to check out glucomannan.
Glucomannan is not a magic bullet you take as a supplement to trigger effortless shrinkage. The only way to lose weight and keep it off is by changing your lifestyle, including eating and exercise habits that may have played key roles along the way.
But glucomannan may be a smart supplement choice that can actually help you lose more weight as part of the program or plan you’ve chosen for slimming down. Let’s see why it works.
The elephant yam, also known as konjac, grows in tropical areas of Eastern Asia; glucomannan is a water-soluble fiber making up nearly half the dry weight of the plant’s root. It’s been used for centuries in Asian herbal medicines, as well as traditional dishes noodles and tofu.
Glucomannan is among the most viscous of all known fibers, and can absorbs up to 50 times its weight in water.
Depending on which recommendation you favor, take a gram of glucomannan (tablet or capsule) 30 – 60 minutes before meals with a big glass of water. It expands in your stomach as it absorbs the water.
When you eat after taking glucomannan, you feel full after consuming a smaller portion that usual. Dietary fiber trips the meter for satiation quickly, and that sensation of “enough” lasts longer; more time passes before you get hungry again. (2)
Glucomannan is low in calories, and it’s been used as a weight loss aid, for controlling blood sugar, and correcting problems with constipation. (3)
High-fiber diets have plenty of positive health effects. To hit that mark, women need to eat 25 grams daily, and men should shoot for 38. (4)
Most Americans fall short of these recommendations (5), which could be a contributing factor to carrying extra weight. (6) Research suggests different fibers can have varying effects on the body, and glucomannan formulas got high marks in a recent weight loss study of 176 healthy overweight subjects following a restricted-calorie diet.
During the five-week trial, three types of glucomannan supplements were tested, each with a different dosage; two had other types of fiber added as well. Participants taking supplements with glucomannan lost anywhere from 3 to 6 pounds more than the control group taking placebos. (7)
Glucomannan is usually tolerated well in doses of 2 – 4 grams daily (1 gram before a meal), and can result in significant weight loss for people who are overweight and obese when used in combination with restricted calorie diets. (8)
In one small trial, 20 subjects took glucomannan with water an hour before eating, and dropped an average of 5.5 pounds over 8 weeks. No reactions to the supplement were reported. (9)
Besides helping you drop extra weight, glucomannan can have positive effects on other health markers cholesterol levels and blood triglycerides. One analysis of 14 studies showed subjects reduced Body Mass Index (BMI), lowered total cholesterol and reduced blood triglycerides. Fasting blood sugar readings were also improved by taking glucomannan. (10)
Since cardiovascular disease is the number one cause of death worldwide (11), taking glucomannan could decrease the risk of suffering a heart attack, as well as cut your chances of developing type 2 diabetes.
Patients suffering from chronic constipation showed improvement during a 10-day treatment with glucomannan; time spans for food to move through the gastrointestinal tract were shorter when the supplement was used, and returned to previous ranges after they stopped taking it. (12)
In another longer study with chronic constipation patients lasting a month, similar results were noted, and researchers recommended glucomannan as an ideal therapy for the condition. (13)
Glucomannan performs another good service in the gut: feeding the friendly intestinal bacteria. Preliminary studies show correlations between healthy gut bacteria and weight control. (14, 15)
While glucomannan is considered safe, it will only help as a weight-loss strategy if you take it before meals.
Because it absorbs liquid so quickly, getting a capsule or tablet stuck in your throat could cause blockage of the esophagus, leading to obstruction of the airway. Take supplements with generous amounts of water or another liquid to prevent this hazard.
It is not safe for anyone with a swallowing disorder or problems with esophagus function to take glucomannan. (16)
Diabetics taking a sulfonylurea medication to stimulate insulin release from the pancreas should pay attention to timing. Take meds at least an hour before glucomannan, or wait 4 hours afterward. Use the same rule for birth control pills. Since the passage of food from the stomach is delayed by glucomannan, it can decrease the effectiveness of any oral medication. (17)
Very few side effects have been reported by subjects using glucomannan; some experience diarrhea or loose stools, bloating or flatulence. Be sure to follow recommended dosage. More is not better, and could create discomfort.
Glucomannan inhibits the absorption of protein and fats; since this is true of all soluble fiber, including those found in any fiber-rich foods, fruits and vegetables, it’s not cause for concern.
A variety of food products with added glucomannan are available in addition to fiber supplements in pill or capsule form. One popular choice is noodles, which are gelatinous and absorb the flavor of seasonings or sauces for a tasty way to introduce more fiber into meals.
Upping the fiber quotient of your diet can contribute to weight loss, and eating plenty of fiber-rich foods is the tried and true method for accomplishing that.
Summary: If you’re committing to a weight-loss program and want to add a supplement that’s helped others with the same goal, glucomannan appears to be effective and safe.
The Fiber Supplement for Weight Loss That Dr. Oz Loves
What is glucomannan? And is the fiber supplement for weight loss really “the best appetite suppressant?” Here's what you need to know
With new weight-loss supplements coming out all the time, it's hard to know which ones really work and which ones won't do you any favors. Where does glucomannan (a natural thickening agent) fall on the spectrum? According to the famed Dr. Oz, it's “one of the best ways to control your hunger,” “the best appetite suppressant,” and “nature's skinny sponge.”
To find out if glucomannan lives up to the hype, we took a closer look at the so-called miracle supplement. Here's what you need to know about glucomannan, glucomannan powder, and glucomannan benefits:
What is glucomannan?
Glucomannan is a sugar made from the root of the konjac plant that has been used for centuries in traditional Japanese cooking as a thickener or gelling agent.
It's so renowned in Japan that it even has its own nickname-“the broom of the intestines”-which gives you a pretty good idea of how it works.
For just a few calories, glucomannan creates a sense of fullness by absorbing water and expanding to form a bulky fiber in your stomach.
“When consumed, glucomannan “sponges” up water in the digestive tract, reducing the absorption of carbs and cholesterol and thus supporting weight loss. […] This supplement also makes you feel full without leaving you gassy or bloated,” Dr. Oz explains.
The “bulky fiber” is then expelled from your body via the natural route. This cleansing effect has been said to help with a host of medical woes reducing cholesterol, helping control blood sugar in people with type 2 diabetes, and constipation.
The glucomannan benefits
While the research is still evolving and the FDA has not given its approval to any glucomannan product's health or weight loss claims, preliminary studies are promising.
In one 2007 study published in the British Journal of Nutrition, participants taking a glucomannan and psyllium husk combination supplement lost approximately 10 pounds in 16 weeks compared to 1.7 pounds lost in the placebo group.
Another study using only glucomannan showed an average of 5.5 pounds lost over eight weeks, without making any other diet or lifestyle changes.
Side effects of glucomannan
With no harsh chemicals, strange drugs, or additives, glucomannan powder (flour) and capsules are considered “ly safe” to use as an appetite suppressant. But there are a few side effects of glucomannan to watch out for. First and foremost, you need to be vigilant about drinking enough water. Dr.
Oz advises drinking 8 ounces of water with 1 gram of glucomannan before each meal. If you don't drink enough, the fiber can literally gum up your digestive system, causing intestinal blockages and, in rare cases, choking by blocking your throat.
Also, one woman's “cleanse” is another woman's date-night disaster so start slowly and work up to the full dosage to see how your body handles it.
If you're interested in trying glucomannan, experts recommend taking it 15-30 minutes before a meal. (Again, don't forget to drink enough water with it.) Here's a quick rundown of the different forms of the glucomannan and all it's supplement forms:
Glucomannan powder: Practically tasteless, glucomannan powder is great for mixing into smoothies and other foods. Bonus: It adds a nice thick consistency.
Glucomannan in food products: Japanese shirataki noodles (also marketed as “miracle noodles”) are the most famous glucomannan food product. They're a little strange at first (It helped me not to think of them as noodles but more stringy Jell-O…with a fishy smell.) Other products gummy candies and chews are also available.
Glucomannan powder tablets: Glucomannan supplements are probably the most convenient, if not the most tasty, option. However, while occurrences are rare, solid tablets are more ly than other forms of glucomannan to cause the previously mentioned blockages of the throat and intestines.
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Glucomannan: Benefits, Side-effects, Dosage
Find out all about glucomannan, including what it does, the benefits to taking it and how much you might need
What is glucomannan and what does it do?
Glucomannan, or konjac as it is sometimes known, is a natural, water-soluble fibre derived from the roots of a south-east Asian plant called the elephant yam.1 It has been traditionally used by the Chinese to detoxify and ease symptoms of asthma, and is still used to make noodles and tofu.2
As with any fibre, glucomannan can help you feel more satisfied after eating, but what makes it interesting to scientists is that glucomannan has extraordinary water absorption capacities – it’s able to absorb up to 50 times its own weight in water!3
Glucomannan is often used as a bulking agent in foods, appearing as E425 on food labels.4 It’s also available as capsules and powder, and is added to some diet foods such as pastas and noodles.
What does glucomannan do in the body?
It may help you maintain your weight
all soluble fibres, glucomannan is highly absorbent, binding to water to form a gel.5 This helps:6
- create a sensation of fullness that can reduce appetite
- delay stomach emptying, keeping you feeling fuller for longer
- break down carbohydrates more slowly, stabilising post-meal blood sugar levels
- decreases absorption of fat
A 2005 study by Norway’s University of Tromso reported that dieters who took glucomannan lost more weight than those taking other high-fibre supplements.7 However, a 2013 study in Journal of Obesity found it had no effect on weight.8
It may support gut health
As a viscous dietary fibre, glucomannan is the favourite food for certain friendly bacteria in our guts. A 2010 laboratory study by the University of Reading found that it helped encourage healthy levels of gut bacteria populations, for example bifidobacterium, but more research on humans is still needed.9
And all fibres, glucomannan can reduce constipation by increasing bulk, and speeding up food transit time through the colon.10
It can lower cholesterol levels
According to a 2008 review of evidence in The American Journal of Clinical Nutrition, glucomannan can reduce levels of total cholesterol and cause a drop in ‘bad’ LDL cholesterol, too. Researchers suggested that glucomannan has this effect by altering both the way cholesterol is produced in the liver and how fats in the body are stored or used for energy.11
How much glucomannan is safe to take?
A dose of around 2g to 4g per day has been used safely in studies, but always read the packaging or food label first.12
Take glucomannan 15 minutes to an hour before a meal, and make sure you swallow it with 1-2 glasses of fluid to avoid it expanding before it reaches your stomach, as this could be dangerous.13
Glucomannan has not been proved safe for the following people:
- pregnant or breastfeeding women
If you are diabetic, speak to your doctor before taking glucomannan as it can reduce the absorption of some diabetes medications.14
What are the side-effects of taking glucomannan?
Generally, glucomannan is well-tolerated. Mild side-effects can include:15
- soft stools
Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies.
1. Keithley J, Swanson B. Glucomannan and obesity: a critical review
2. Chua M, et al. Traditional uses and potential health benefits of Amorphophallus konjac K. Koch ex N.E.Br
3. Keithley JK, et al.
Safety and Efficacy of Glucomannan for Weight Loss in Overweight and Moderately Obese Adults
4. Mortensen A. Re‐evaluation of konjac gum (E 425 i) and konjac glucomannan (E 425 ii) as food additives5. As Source 3
6. J. Slavin, H. Green.
British Nutrition Foundation. Dietary fibre and satiety
7. Birketvedt GS, et al. Experiences with three different fiber supplements in weight reduction8. As Source 3
9. Connolly ML, Lovegrove JA, Tuohy KM. Konjac glucomannan hydrolysate beneficially modulates bacterial composition and activity within the faecal microbiota
10. Chen HL, et al. Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults
11. Sood N, Baker WL, Coleman CI. Effect of glucomannan on plasma lipid and glucose concentrations, body weight, and blood pressure: systematic review and meta-analysis12. As Source 1
13. Atli Arnarson. Healthline. Glucomannan – Is It an Effective Weight Loss Supplement?
14. As above
15. As Source 13
15 Glucomannan Health Benefits, Risks & Side Effects
Glucomannan is a complex sugar that may lower cholesterol and blood sugar and prevent constipation. Early research suggests that it may also be helpful for managing weight, improving gut health, and protecting the skin. Read on for more about its potential.
What Is Glucomannan?
Glucomannan is a complex sugar and soluble fiber. The most commonly used type is konjac glucomannan, which is taken from the tubers of konjac, a plant native to Asia .
It is also extracted from :
- Eastern white pine
It absorbs water extremely well and has the highest viscosity of any known dietary fiber .
A few grams of glucomannan powder can turn a whole glass (eight ounces) of water into a gel.
This fiber has been used in food for thickening and binding, as a fat substitute, and as a preservative .
It has gained popularity as a dietary supplement, mainly due to its reputation for weight loss.
Mechanisms of Action
Glucomannan works by:
- Taking up space in the stomach, making you feel full and eat less
- Decreasing the amount of hunger hormone ghrelin 
- Decreasing the absorption of nutrients (proteins, fats, and sugars) [4, 1]
- Removing bile acids 
- Promoting the growth of good bacteria in the gut [6, 7]
Potential Benefits of Glucomannan
Glucomannan is approved as a food additive, but supplements have not been approved by the FDA for medical use. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.
Bile acids are made from cholesterol. Glucomannan binds to bile acids and helps remove them from the body. As a result, the body has to convert more cholesterol into bile acids, lowering cholesterol levels .
In two meta-analyses, one including 12 studies and the other including 14 studies, this supplement significantly loweredLDL andnon-HDL cholesterol types. LDL and non-HDL cholesterol increase the risk of heart disease when elevated [8, 9].
In a with 120 people with high cholesterol, glucomannan combined with policosanol or chromium-polynicotinate reduced total and LDL cholesterol but didn’t affect HDL or triglyceride levels .
In another trial, 2.4 g/day of chitosan and glucomannan reduced total, LDL, and HDL cholesterol but not triglycerides in 21 overweight people .
According to some researchers, glucomannan may cause a more gradual absorption of sugar, which reduces spikes in blood sugar levels .
In a study of 22 diabetic subjects, this fiber helped decrease blood glucose levels and cholesterol .
In addition, in two studies, each of 20 diabetic adults, glucomannan taken before a meal decreased the spike in blood sugar levels and decreased appetite by decreasing ghrelin [13, 3].
Similarly, glucomannan-enriched food reduced blood sugar levels in type 2 diabetic patients .
In another study of 11 type 2 diabetic patients, this supplement didn’t lower blood sugar, but it lowered total: HDL cholesterol ratio and blood pressure .
A study of 34 pregnant women showed that this fiber safely decreased blood glucose levels in both diabetic and non-diabetic patients .
In six studies, glucomannan relieved constipation without side-effects [17, 18, 19, 6, 7, 20].
However, in a study of 72 children, this fiber was not more effective than the placebo in treating constipation .
Insufficient Evidence For
The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of glucomannan for any of the below-listed uses. Remember to speak with a doctor before taking glucomannan supplements, and never use them in place of something your doctor recommends or prescribes.
4) Weight Management
In multiple clinical studies, glucomannan supplementation increased weight loss compared to a placebo [22, 23, 24, 25, 26].
However, in other studies, it did not have a significant impact on weight loss [27, 28, 29].
Glucomannan may help with weight loss in certain groups of people but doesn’t seem to have an effect on others. Future studies will be required to clarify.
5) Gut Health
Glucomannan increased the proportion of beneficial gut bacteria (lactic acid bacteria and bifidobacteria) in seven constipated subjects and eight healthy adults [6, 7].
A small dose of this fiber also increased the number of beneficial bacteria and the production of short-chain fatty acids (SCFAs) in the gut of mice and rats [30, 31].
6) Polycystic Ovary Syndrome
PCOS (polycystic ovary syndrome) can cause insulin resistance. In a study of 30 women with PCOS, glucomannan supplements reduced their glucose and insulin levels .
In a study with 48 hyperthyroid patients, those who received glucomannan, in addition to standard therapy, had significantly lower thyroid hormone levels during the first weeks of treatment .
8) Skin Damage
Glucomannan decreased UV-induced skin redness in 5 human volunteers and protected skin cells against UVB-induced damage .
Animal & Cell Studies (Lacking Evidence)
No clinical evidence supports the use of glucomannan for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
Glucomannan and probiotic bacteria blocked the growth of acne-causing bacteria in a cell study .
This supplement decreased inflammation in rats with arthritis .
It also decreased gut and skin inflammation in mice [37, 38].
In these studies, glucomannan decreased Th2 response (IL-4 and IL-13).
This supplement prevented allergic rhinitis and dermatitis (nose and skin allergies) in mice [39, 40].
It did so by decreasing IgE levels [41, 42].
12) Antioxidant Activity
This supplement increased antioxidant and antioxidant enzyme levels in mice and rats [43, 44, 45].
Long-term feeding with this supplement delays aging in mice and rats [46, 47].
Side Effects & Precautions
Glucomannan has been recognized as safe by the FDA since 1994. Since 1996, it’s been approved as a binder in the food industry [48, 1].
Side effects of supplementation may include flatulence, stomach pain, and gut obstruction [2, 49].
To prevent it from expanding prematurely and blocking the gut, make sure you take enough water or other liquids. Some people also recommend not taking it immediately before going to bed.
Glucomannan may, in addition, interfere with the bioavailability of ingested drugs [2, 49].
This supplement lowers blood glucose. Mixed with diabetic medication, it can cause low blood sugar .
To avoid adverse effects and unexpected interactions, talk to your doctor before using glucomannan supplements.
There is no safe and effective dose of glucomannan for any health purpose because no sufficiently powered study has been conducted to determine one. That being said, clinical studies have found benefits associated with certain doses.
Studies usually administer 1 to 5 grams, 1 to 3 times a day. Subjects take the supplements with water, an hour before a meal [23, 24, 25, 9, 18].
Users say glucomannan is good for:
- Controlling blood sugar levels
- Weight loss
- Hunger control
- Lowering cholesterol
- Insulin resistance in PCOS
However, some also report:
- Bloating and gas
All About Glucomannan
Glucomannan, from konjac root, is a form of beneficial soluble fiber that can improve bowel health, blood sugar and lipids, and other health conditions. It can also help you lose fat and stay lean by improving satiety and appetite hormones.
To lose fat, you have to eat less. Simple enough. But it’s hard to get enough fiber when you’re eating less food. Inadequate fiber often means more hunger. More hunger means you want to eat more.
What to do?
Glucomannan, a soluble fiber from konjac root, may be one supplement that meets both these needs — adequate fiber plus greater satiety. It may have many other health benefits too.
What are soluble fibers?
Soluble fibers are a form of so-called “complex” carbohydrate (which means that their more elaborate molecular structure is harder for our bodies to break down) that are soluble in water. In liquid, soluble fibers form viscous gels. For instance, fruit pectin is used to thicken jams and jellies, while xanthan gum is used as an emulsifier that makes foods creamier.
Soluble fibers are also great bacteria food (which earns soluble fiber the term prebiotic). Our gastrointestinal bacteria eagerly ferment soluble fibers, creating byproducts such as valuable nutrients or not-so-desirable gases.
Soluble fibers are found in foods :
- beans and legumes
- grains such as oats, rye, and barley
- some fruits such as plums/prunes, apples, pears, berries, and bananas
- some vegetables, such as the onion family; the brassica family; and Jerusalem artichokes (root vegetables/tubers are often high in soluble fibers)
- some seeds, such as chia and psyllium
For more on this, see All About Fiber.
From konjac root to glucomannan
many tubers, the root of the konjac plant (Amorphophallus konjac) is high in soluble fiber. This soluble fibre is used to manufacture glucomannan (GM) supplements.
Konjac also appears in East Asian cuisine, often as shirataki noodles or a gel that is cut up and served with dipping sauce. It’s generally prized for its gelatinous texture rather than taste, and takes on the taste of whatever it’s cooked, marinated, or dipped in.
Sashimi konnyaku (konjac sashimi)
From konjac, manufacturers can produce flour or powder, along with “foods” such as noodles, gels, and even candies (although these aren’t recommended for consumption).
What does glucomannan do?
Although konjac has long been used in China, Japan and South East Asia as a food source and as a traditional medicine, Western researchers have only been interested in GM’s health benefits since about the 1980s.
Glucomannan/konjac flour or powder is highly absorbent, and can suck up tremendous amounts of liquid. In an article on glucomannan, T-Nation included a video showing just how much a wee bit of GM expands when water is added.
Helps us feel fuller, longer
Because it can hold so much water and form a gel, GM helps us feel more satisfied with meals. This means we can eat less but feel more satisfied for longer. Eating less means fat loss.
Studies looking at adding GM to calorie-restricted diets have consistently found that GM groups lose more fat than the non-fiber’d up groups. In one study (Birketvedt GS, et al. 2005), the GM group dropped an additional .8/kg (1.75 lb) on average over 5 weeks compared to the control group.
This effect of feeling full is not necessarily obvious — having a full gut does not always leave one feeling satisfied. As many dieters know, a stomach that’s simply stretched (e.g. from being full of water) doesn’t necessarily result in a lack of desire to eat more. “Mechanical” fullness doesn’t always mean “real” satisfaction.
However, a study of people with Type 2 diabetes (Grill 2010) showed that key hunger signals (such as ghrelin) decreased after taking a meal with GM in it. GM seems to trip sensors in the gut/brain to tell them that less food is more satisfying.
Better carbohydrate tolerance & lipid profile
Along with its effects on physical fullness, GM may improve satiety and fat loss by improving our blood sugar and lipid profile.
One review (Keithley and Swanson 2005) found that 2-4 g of GM each day enhanced dieters’ weight loss efforts, along with other positive side effects improved blood lipids, carb tolerance, and satiety. Being better able to handle starchy carbs means better insulin sensitivity, which means better appetite control and fewer blood sugar swings or cravings.
One of the earliest findings with GM (Walsh 1984) showed lower serum cholesterol and LDL. And compared to one of the most popular soluble fiber supplements, psyllium, GM seems to have better overall results on blood lipids.
Gut health is an indicator of overall well being. This includes good gastric motility (stuff moving through the pipes) and a healthy bacterial flora. (Indeed, gut dysbiosis, or an overgrowth/imbalance of the wrong bacterial types, has been connected to obesity.)
Lowcarb dieters know the nightmare that is a good bowel movement while the body adjusts to lower intakes of grains and other sources of fiber. Tolerable bowel movements while eating less food can be a challenge.
Lots of dieters try psyllium husk or bran as a solution to constipation. But along with choosing higher-fiber whole foods, going the soluble fiber route with GM may be a better choice.
Besides regular bowel movements, a study (Chen 2006) found that the group using GM also showed a significant increase in helpful bifidobacteria, lactobacilli and total bacteria — the friendly gut bacteria we want. The GM supplement also promoted colonic fermentation, as shown in the decreased fecal pH. That’s a good thing.
Probiotic foods (such as sauerkraut, kimchi, miso, etc.) along with GM have been shown to reduce acne. (Just FYI: Eat it, don’t smear it on your face.)
No food/supplement overview would be complete without evaluating its influence on cancer. GM’s benefits for gastrointestinal flora may help reduce precancerous risk factors of colon cancer.
GM may help with hyperthyroid symptoms, as Cassandra Forsythe suggests.
(Also check out the rest of Cassandra’s pieces on GM.)
Because GM expands so readily in water, people have choked on the powder or GM candies by trying to swallow them dry. Imagine a balloon blowing up in your mouth and throat and you get the idea.
Thus, take GM either in food format (e.g. as shirataki noodles or konjac gel in your favourite Korean or Japanese dishes) or as a powder added to food or dissolved into a Super Shake. You can also take it as capsules — be sure to have them with plenty of water. However, the pills aren’t as strongly recommended.
Otherwise, GM has been shown to be safe for both adults and kids.
Start with small doses of GM. Clinical studies used only about 1-3 g per meal on average. We recommend one very small dose per day to start.
Going overboard may cause bloating, gas and related discomfort.
How to take glucomannan
There are quite a few ways to get GM into one’s diet.
- Konjac flour (aka GM powder) is available from a variety of resellers – but it’s not exactly cheap, at around $18 USD/500 grams.
- Shirataki (or shiratake) noodles, which you can find in Asian grocery stores, can be used in traditional East Asian dishes or as a pasta substitute. Rinse noodles off first as they have a funky smell when first the package. You can also try the konjac gel (cut it up into little pieces and serve with dipping sauce), but it can be an acquired taste/texture.
- We don’t generally recommend GM pills, but one Canadian product that’s not bad is PGX, which is mostly GM along with sodium alginate, and alas, xanthan gum (and various stabilizers).
- If you do get GM pills, pop the capsules open and dissolve them in some water first, or mix them into some liquid-y food.
Again, be sure to drink lots of water with GM and/or dissolve well in liquid before ingesting.
Konnyaku (konjac) gel. You may, um, want to cut it up into chunks or something. Or throw a sprig of parsley on there.
Summary & recommendations
GM can improve many measures of bowel health, such as gastric motility (aka having healthy and appropriately frequent bowel movements) and the health of good GI bacteria.
GM can improve blood sugar control and blood lipids (e.g. serum cholesterol and lipoproteins).
GM can help you lose weight by keeping you fuller longer, and possibly affecting appetite hormones.
For safety, take GM with lots of liquid.
Check with your doctor if you’re on any medication that may be contraindicated, or if you have trouble swallowing.
Click here to view the information sources referenced in this article.
Al-Ghazzewi FH, & Tester RF (2009). Effect of konjac glucomannan hydrolysates and probiotics on the growth of the skin bacterium Propionibacterium acnes in vitro. Int J Cosmet Sci 31:139-142.
Birketvedt GS, et al. (2005). Experiences with three different fiber supplements in weight reduction. Med Sci Monit 11:PI5-8.
Chen HL, et al. (2006). Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults. Nutrition 22:1112-1119.
deFonseka A & Kaunitz J. (2009). Gut sensing mechanisms. Curr Gastroenterol Rep 11:442-447.
Grill, H. (2010). Leptin and the systems neuroscience of meal size control. Front Neuroendocrinol 31:61-78.
Keithley J & Swanson B (2005). Glucomannan and obesity: a critical review. Altern Ther Health Med 11:30-34.
Chearskul S, et al. (2009). Brief report Immediate and long-term effects of glucomannan on total ghrelin and leptin in type 2 diabetes mellitus. Diabetes Res Clin Pract 83:e40-e42.
Chua M, et al. (2010). Traditional uses and potential health benefits of Amorphophallus konjac Ethnopharmacol. 24;128(2):268-78. Epub 2010 Jan 15.
Marsicano LJ, et al. (1995). Use of glucomannan dietary fiber in changes in intestinal habit G.E.N. 49:7-14.
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Safety and Efficacy of Glucomannan for Weight Loss in Overweight and Moderately Obese Adults
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