OTHER NAMES
• Konjac • Konjac Mannan •
Amorphophallus konjac
Glucomannan has been a popular medicine and food for thousands of years in Asia. The glucomannan plant grows in Indonesia and Japan, and its plant tubers yield a chemical known as konjac mannan. The chemical is used to make konjac powder or flour, which can then be molded into noodles, rubbery jelly, and other foods.
USES
Glucomannan is used for weight loss, high cholesterol, and diabetes. It is also used as a laxative. It contains soluble fiber that may delay glucose absorption and decrease cholesterol absorption. Glucomannan is now thought to be helpful for those who are insulin resistant, but who do not yet have diabetes, by improving insulin resistance when added to carbohydrate-containing foods. In general, people can safely eat glucomannan as food, but should be careful about taking glucomannan in tablet form due to choking hazards. Therefore, glucomannan should be consumed in a powder or capsule form.
DOSE
Doses for diabetes and high cholesterol range from 3.6 to 10.6 grams (g) daily.
STUDIES
There have been a variety of studies using glucomannan in people with diabetes. Most have involved a small number of patients.
• A study examined glucomannan in 11 patients receiving treatment for type 2 diabetes, high cholesterol, and high blood pressure. The patients were initially placed on the National Cholesterol Education Program (NCEP) Step-2 diet that limited cholesterol and saturated fat intake for 8 weeks. After the diet treatment phase, patients were randomized for 3 weeks to a placebo (dummy pill) or a treatment consisting of konjac biscuits eaten three times a day to provide 0.7 g konjac per 100 calories eaten. At the end of 3 weeks, patients had a 2-week washout and were then crossed over to the other treatment group. Fasting glucose decreased significantly from 173 to 154 milligrams/deciliter (mg/dl) in the konjac group, whereas it decreased by 1.5%from 167 mg/dl in the placebo group, a non-significant amount. Total cholesterol decreased in both the treatment and the placebo group, by 16% and 5% respectively. LDL cholesterol decreased significantly from 150 to 113 mg/dl in the glucomannan group and from 137 to 130 mg/dl in the placebo group. Systolic pressure decreased significantly by 5.5% in the glucomannan group and increased by 1.4%in the placebo group. There were no differences in diastolic blood pressure.
• A separate, well-designed study (randomized, double- blind, placebo-controlled) was done in 22 patients with type 2 diabetes and high cholesterol. Patients were on oral diabetes medications but not on cholesterol medications. The patients followed an NCEP diet for 2 months and were then randomized to a placebo or glucomannan. After 28 days, they were crossed over to the other group without a washout. The dose used was lower than in the previous study, 0.24 grams glucomannan per 100 calories eaten. LDL cholesterol decreased significantly in the glucomannan group from 154 to 138 mg/dl while it increased from 150 to 165 mg/dl in the placebo group. HDL cholesterol (so-called “good” cholesterol) increased significantly from 44 to 46 mg/dl in the glucomannan group. Fasting glucose declined significantly in the glucomannan group from 169 to 148 mg/dl; in the placebo group, it increased from 157 173 mg/dl. Two-hour post-meal glucose also declined by 30 mg/dl in the glucomannan group.
SIDE EFFECTS AND DRUG INTERACTIONS
The most dangerous adverse effect is choking, which has been reported with the tablet form but not with powders or capsules. Glucomannan may cause upset stomach and may add to the effectiveness of diabetes and cholesterol-lowering medications. should not be taken at the same time as oil-soluble vitamins such as A, D, E, and K.