Native to Asia, the konjac plant (Amorphophallus konjac) is characterized by its heavy tubers (10 pounds or more in weight) and blotchy, snakeskin-patterned stem. It is most known as a source of glucomannan, a soluble, fermentable, and highly viscous dietary fiber derived from the roots of the plant.
The konjac plant has been used as a source of both food and medicine in traditional Asian practices for more than a thousand years. More recently, glucomannan extracts derived from the konjac plant have been used as a dietary supplement or as a source of mannose, a sugar substitute in food products.
Given the highly viscous nature of glucomannan fiber, it effectively absorbs water in the digestive tract and decreases the absorption of carbohydrates and cholesterol. As such, since the 1980s, Western medicinal practices have valued glucomannan for its potential to reduce cholesterol levels, constipation, blood sugar, and weight. It has also been explored as a component of artificial skin products, and in the treatment of high blood pressure and hyperthyroidism (overactive thyroid), though additional research in these areas is needed.
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Select combination products: Appe-Trim™ (glucomannan and guar gum); Glucosahl™ (glucomannan, guar gum, and alginate).
Note: Although many different species of plants and yeast contain glucomannan (e.g., Candida utilis), this summary will focus only on the glucomannan derived from the konjac plant (Amorphophallus konjac).
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Preliminary research suggests that glucomannan improves lipid levels in the body by increasing the elimination of neutral sterols and bile acids in the feces. In particular, glucomannan has been shown to decrease cholesterol by interfering with its transport. Additional research is needed to examine its effects in persons with high cholesterol or those taking lipid-lowering agents.
Due to its bulking effect on feces and its increased elimination of bacteria that affect fecal movement, glucomannan has been shown to increase the number of bowel movements. Glucomannan has also been suggested as improving symptoms of abdominal and excretory pain. Further research regarding glucomannan's use, efficacy, and long-term safety is needed in this area.
In persons with type 2 diabetes, preliminary research has shown that glucomannan lowers both fasting and postprandial (after eating) blood glucose levels. Additional research is needed to investigate its possible interaction with other blood sugar-lowering agents.
Preliminary research suggests that glucomannan, most often in combination with a reduced-calorie diet, increases weight loss by increasing the time to swallow, feelings of fullness, and energy lost via the feces. Further comparative and long-term research in this area is needed.
High blood pressure
Limited research suggests that glucomannan lowers blood pressure. However, findings in this area vary between studies, and definitive conclusions are lacking. Additional research is needed to investigate its long-term effects and its possible interaction with other blood pressure-lowering agents.
According to preliminary research, glucomannan may reduce levels of various thyroid hormones in patients with newly diagnosed hyperthyroidism. Further research is required before conclusions can be drawn.
Hypoglycemia (low blood sugar)
In patients with previous gastric surgery, preliminary research suggests glucomannan may improve reactive low blood sugar. Further research is required before conclusions can be drawn.
Impaired glucose tolerance
In children with dumping syndrome (rapid transit of gastrointestinal tract contents), preliminary research suggests that glucomannan may improve glucose tolerance. However, reports of increased side effects warrant additional research in this area before conclusions about its suitability in this population can be made.