Glucomannan is a natural vegetable fiber obtained from the root of a plant known as konjac (
Amorphophallus konjac). Glucomannan is commonly used in Asian health foods, and several herbal supplements now contain glucomannan. In addition to its use in foods, glucomannan is often claimed to be useful for the following purposes:
Unlike many other herbal supplements, there is actually a fair amount of evidence that glucomannan may be effective for these uses.
Many studies have evaluated glucomannan for a variety of uses. In general, these studies have suggested that glucomannan is probably safe and effective for these uses. It has long been known that a high-fiber diet can help with weight loss. Fiber tends to help people feel fuller for a longer period of time. Small studies have suggested that glucomannan may be effective for weight loss, although more research is needed.
Additionally, studies have generally suggested that glucomannan is effective for treating constipation,
high cholesterol, and type 2
diabetes. It is important to note that these studies were usually small and generally did not compare glucomannan to a placebo (a "sugar pill" with no active ingredient). While further research is needed to confirm these findings, it makes sense that glucomannan works for these problems, because it is a fiber supplement (and fiber is often helpful for these conditions).
There is also some evidence that glucomannan can help prevent food poisoning from food contaminants and toxins (although studies have focused on animals for this use). Recent research has also suggested that glucomannan can help treat eczema-like skin reactions in mice. There is also some interest in using glucomannan as an inactive ingredient to help deliver other drugs specifically to the large intestine.
