Glucomannan is the Western name for vegetable fibers derived from an
Asian plant family known as konjac. Glucomannan does not dissolve in
water, but forms a thick, gooey gel when exposed to fluids. The body
does not digest glucomannan, so the resulting large soft mass moves
through the intestines and may trigger intestinal muscle contractions.
Therefore, glucomannan is thought to be an effective bulk-type
laxative, even though it may take up to 12 hours to be effective.
Glucomannan
vs. Obesity and Cholesterol
Glucomannan has also been studied for treating obesity, diabetes,
and high cholesterol. Studies in both adults and children with severe
obesity showed varying degrees of weight loss associated either with
taking supplemental glucomannan or with replacing some of the usual
diet with foods made from glucomannan (konjac) flour--the dried and
ground tuber (underground stem) of the plant. Generally, glucomannan is
believed to discourage overeating because it creates a feeling of
fullness after the fiber in it swells. Because stomach contents may
stay in the stomach longer, the individual does not feel hungry as
often. However, in most of the research studying glucomannan for weight
loss, study participants also drank large amounts of water and followed
a reduced-calorie diet.
Blood Sugar
Levels
Possibly due to the same delay in stomach emptying, glucomannan may
improve blood sugar levels in individuals with diabetes. Because the
absorption of carbohydrates from foods is slower when glucomannan is
taken, blood sugar levels may not rise as high or as fast as usual.
Some preliminary results from animal studies also suggest that
glucomannan may increase the sensitivity of body tissues to the insulin
that is produced or taken. In several studies, taking glucomannan has
also appeared to lower blood levels of total cholesterol, low-density
lipoproteins (LDL, or "bad" cholesterol), and triglycerides. Although
more research on this possible use of glucomannan is needed,
glucomannan may increase the elimination of cholesterol and its
components from the body. It may also keep bile acids from being
reabsorbed in the intestines, further reducing cholesterol levels in
the blood, because the body uses cholesterol to produce more bile.