GLUCOMANNAN
Glucomannan is a water-soluble, fermentable dietary fiber derived from the root of the elephant yam (also known as konjac). In Asia, the konjac tuber has been used for centuries as an herbal remedy and to make traditional foods. More recently, the purified konjac flour has been used in processed foods as a stabilizer and gelling agent.
Because of the chemical structure of glucomannan, it cannot be digested by salivary and pancreatic enzymes. It passes through the small intestine into the colon where the bacteria present ferment it there. The glucomannan molecule can absorb up to 50 times its weight in water. Because of these two properties, glucomannan has been found to promote weight loss, lower cholesterol and triglycerides, lower blood sugar after meals and improve constipation.
The ability of glucomannan to lower weight has been studied in several clinical trials. Seven trials of short-term duration showed weight loss of one to five pounds when 2-4 grams of glucomannan were taken daily. Bloating, flatulence and diarrhea were the only side effects noted. Proposed mechanisms to account for the ability of glucomannan to lower weight include delayed gastric emptying, sense of increased satiety (feeling full from a meal), slowing of small bowel transit time of food, slowed absorption of food in the small intestine and accelerated delivery of food to the end of the small intestine.
Recent research on people with type 2 diabetics and elevated cholesterol showed that taking glucomannan did not cause any weight loss but it did lower blood sugar, total cholesterol and LDL cholesterol. In addition, systolic blood pressure was lowered. Again, only minor intestinal symptoms were noted in a few people.
Glucomannan is available in capsules, a powdered drink mix and in food products. Tablets are to be avoided since they can swell upon contact with water and obstruct the esophagus. Likewise, glucomannan jelly candies have been banned in the USA because of obstruction. People who take drugs or insulin to lower blood sugar should be aware that taking glucomannan can lower blood sugar and might cause hypoglycemia reactions. Patients who take prescription drugs may have lowered absorption of the medication into the blood due to the effect of the glucomannan. Taking the medication one hour before or 4 hours after the glucomannan should be safe.
Although further research is needed, glucomannan shows promise of being a safe, effective and cheap way to lose weight and to lower cholesterol and blood sugar. Consult your physician before taking glucomannan or other supplements if you have any medical condition or are taking prescription medications.
Daniel Blodgett MD