Glucomannan and psyllium are both bulk-forming laxatives used to treat constipation, according to PubMed Health. Glucomannan and psyllium absorb liquid in the intestines, causing it to swell, and create larger stools, which are easier to pass. The Cleveland Clinic reports although glucomannan has shown promise in clinical research studies, there’s currently an insufficient amount of evidence proving its effectiveness. On the contrary, psyllium has been found beneficial, and is commonly found in over-the-counter laxatives such as Metamucil, according to the University of Maryland Medical Center.
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Glucomannan is derived from the root of a konjac plant, known as Amorphopallus konjac. Psyllium comes from a shrub-like herb termed Plantago ovata, which grows worldwide. The University of Maryland Medical Center reports each Plantago ovato can produce up to 15,000 seeds from which the psyllium husk is derived.
As soluble dietary fibers, glucomannan and psyllium create larger, bulkier stool when combined with water. The combined mixture causes swelling and stimulates the intestines to contract, assisting the stool to move through the colon more smoothly. It also makes the passage of stool from the body easier, as it requires less pressure and straining, thus eliminating constipation.
Glucomannan has also been shown to lower blood cholesterol levels and promote weight loss. PeaceHealth states that controlled and double-blind research trials have found supplementation with glucomannan substantially decreased total blood cholesterol, LDL cholesterol, and triglycerides. Researchers believe glucomannan has the potential to be used as a weight-loss supplement because in small studies people have lost an average of 5.5 lbs. when taking glucomannan one hour prior each to meal, according to an article published in "International Journal of Obesity" in 1984.
Psyllium may also be used treat irritable bowel syndrome, hemorrhoids and other intestinal problems. Several large, population-based research studies have also suggested that increased fiber intake may reduce the risk of color cancer; however, more studies need to be conducted to confirm these findings.
Glucomannan purified fiber is available as bulk powder and hard-gelatin capsules. Using glucomannan for laxative purposes, you should consume 3 to 4 grams per day. If you plan on lowering cholesterol levels with glucomannan, take anywhere from 4 to 13 grams per day. For weight loss purposes, 1 to 3 grams before each meal has shown to be effective in clinical research.
Psyllium comes in multiple forms: powder, granules, capsule, liquid and wafer. It’s commonly taken one to three times daily, according to PubMed Health. Psyllium powder and granules need to be mixed with 8 ounces of a pleasant-tasting liquid, such as fruit juice, immediately before use. If prescribed wafers, chew thoroughly.
Glucomannan tablets are not considered safe because they may cause blockages of the throat or intestines, termed gastrointestinal obstruction. Several countries have actually banned glucomannan due to its high prevalence of gastrointestinal obstruction. The Cleveland Clinic also recommends that diabetics avoid taking glucomannanm, as it may interfere with blood sugar levels.
Psyllium can potentially cause side effects. If you have one or more of the following symptoms, call your doctor immediately: difficulty breathing, stomach pain, difficulty swallowing, skin rash, itching, nausea or vomiting. Additionally, psyllium should not be taken for longer than one week, unless directed by your doctor, according to the Cleveland Clinic.