Glucomannan benefits and side effects

glucomannan-2Glucomannan is a natural fiber supplement derived from yams that helps dieters lose weight.

Packing around more pounds than we need or like 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 like 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 like 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)

Side Effects

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, like 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.

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