Psyllium is typically available as either black or blond psyllium; however blond psyllium has more applications for health than the black variety. The information in this article is geared toward blond psyllium, as the majority of psyllium products are comprised of this type.
Blond psyllium is most often used for constipation, for softening stools in people with hemorrhoids, fissures, pregnancy, or after surgery. Psyllium is also used as a mild bulking agent, and can be applied in cases of loose stools, irritable bowel syndrome, and colitis.
In addition to its actions on the bowels as a dietary fiber, psyllium is useful in diabetes, for lowering blood lipids, high blood pressure, and as topical treatment for abscesses.
The medicinal parts of psyllium used are its tiny seeds and the husk surrounding them. The seed and husk, when immersed in a liquid environment, absorb the fluid to form a gel-like substance.  Psyllium is known as a water-soluble fiber, and when swallowed will form this gel in the intestines. Oftentimes, purified psyllium seed is available; this consists of only the seed husk, with the inner seed parts removed. There is some concern that the inner seed components (endosperm and plant embryo) are responsible for some psyllium allergy. 
Psyllium has several well-documented uses in medicine. One of the best-known uses for psyllium is treating constipation. Psyllium seed, when it enters the digestive tract, is capable of absorbing large amounts of water and acting as a bulking and softening agent for the stool.  Psyllium has been shown to be comparable to other stronger laxative and stool softening agents. [3, 4]
Psyllium is effective at lowering blood cholesterol in persons with mild to moderate elevations. When taken in amounts close to 10 to 12 grams per day, total cholesterol was lowered in subjects by roughly 3% to 14%, while low-density lipoprotein (LDL) cholesterol was lowered by 5% to 10%. [5, 6] Based on price and its clinical effects at treating blood lipids, psyllium is perhaps one of the most cost effective medicines in this regard.
For treatment of diabetes, psyllium seed husk has the ability to assist the body in lowering blood glucose levels following a meal, which then leads to decreased insulin levels, as well as total cholesterol and LDL cholesterol in patients with type 2 diabetes. [7, 8] Psyllium is effective at lowering blood glucose levels in type one diabetics as well; effectively lowering blood glucose by roughly 14% to 20% following a meal in one particular study. [9, 10] It is important to note that psyllium does not lower blood glucose levels unless they are high; in other words, it will not lower blood glucose levels in people without this condition. 
For diarrhea treatment, psyllium will slow the digestive process by keeping food in the stomach and large intestine for a longer period of time, therefore promoting an increase in the thickness of stool in chronic diarrhea. [12, 13]
Psyllium can also assist in reducing blood pressure; in one study it reduced systolic blood pressure by roughly 8 points and diastolic by about 2 points. 
In conditions such as irritable bowel syndrome (IBS) and ulcerative colitis, psyllium works well as an adjunctive treatment. In IBS, psyllium seems to relieve constipation symptoms, decreasing associated abdominal pain and diarrhea that often occurs.  Similarly, in patients with ulcerative colitis, psyllium can relieve symptoms of abdominal pain, bloating, diarrhea, constipation, urgency, and feeling of incomplete stool evacuation. 
Typical dosing of psyllium seed ranges from, roughly, 5 to 30 grams per day. When taken in larger amounts, it should be administered in divided doses throughout the day. Caution should be used when taking psyllium to ensure adequate intake of water at the same time. Choking on expansive seeds has been a concern as well. Although chances are small, increasing water may assist in optimizing the benefits of psyllium seed.
Psyllium Side effects
Taking psyllium may lead to abdominal cramping, diarrhea, constipation, nausea, and flatulence. There is concern that if not taking with adequate water, psyllium may lead to bowel obstruction or difficulty swallowing in those with swallowing dysfunction. Side effects may be avoided if the dosages are minimal at first, and gradually increased.
Medical literature suggests that psyllium is allergenic select individuals. This is not uncommon as nearly all substances demonstrate the potential for allergic reaction. This risk varies from one substance to another, and some products now carry labels stating that they contain psyllium and may therefore lead to such adverse reactions. 
Psyllium General interactions (supplement, herb, food, lab)
Psyllium may decrease iron absorption.  Psyllium is thought to decrease the absorption of riboflavin (vitamin B-2) as well, although the amount that it does is considered clinically negligible.  As with all forms of fiber, supplements should be taken at different times as fiber acts as a ‘binder’ in the intestines and can prevent or inhibit the absorption of various substances from the gut. This applies to herbal medicines as well; fiber may bind with them and decrease their efficacy.
Lab tests: taking psyllium can decrease cholesterol and LDL levels in the blood, leading to lower test results. Psyllium can lower post-prandial (after eating) blood glucose levels and alter test results as well.
Psyllium Drug interactions
Psyllium may alter absorption of several different types of drugs. Again, being a fiber, psyllium will slow the absorption of these substances from the intestines if taken together. Before taking psyllium with a pharmaceutical medication, one should check to see if there are any existing contraindications. Slowed absorption of drugs from the gut may lead to decreased drug efficacy.
- People with allergies should use caution when taking psyllium, as it may cause allergic reactions in certain people that are prone to psyllium allergy.
- Diabetics: As mentioned, psyllium can lower blood sugar. While this is considered a positive effect amongst diabetics, it may require that the dosing of pharmaceuticals used for diabetes treatment be altered.
- Gastrointestinal: People with narrowed GI tracts, history of fecal impaction, or spastic bowel should avoid psyllium, as they may be susceptible to blockage. 
- Phenylketonuria: This is a condition in which certain people are unable to metabolize the amino acid phenylalanine. Some psyllium products are sweetened with aspartame (Nutrasweet), which contains phenylalanine. 
1. Schwesinger WH, Kurtin WE, Page CP, et al. Soluble dietary fiber protects against cholesterol gallstone formation. Am J Surg 1999;177:307-10.
2. Arlian LG, Vyszenski-Moher DL, Lawrence AT, et al. Antigenic and allergenic analysis of psyllium seed components. J Allergy Clin Immunol 1992;89:866-76.
3. Marlett JA, Li BU, Patrow CJ, Bass P. Comparative laxation of psyllium with and without senna in an ambulatory constipated population. Am J Gastroenterol 1987;82:333-7. 3 Ibid
4. McRorie JW, Daggy BP, Morel JG, et al. Psyllium is superior to docusate sodium for treatment of chronic constipation. Aliment Pharmacol Ther 1998;12:491-7.
5. Anderson JW, Allgood LD, Lawrence A, et al. Cholesterol-lowering effects of psyllium intake adjunctive to diet therapy in men and women with hypercholesterolemia: meta-analysis of 8 controlled trials. Am J Clin Nutr 2000;71:472-9.
6. Sprecher DL, Harris BV, Goldberg AC. Efficacy of psyllium in reducing serum cholesterol levels in hypercholesterolemic patients on high- or low-fat diets. Ann Intern Med 1993;119:545-54.
7. Pastors JG, Blaisdell PW, Balm TK, et al. Psyllium fiber reduces rise in postprandial glucose and insulin concentrations in patients with non-insulin-dependent diabetes. Am J Clin Nutr 1991;53:1431-5.
8. Frati Munari AC, Benitez Pinto W, Raul Ariza Andraca C, Casarrubias M. Lowering glycemic index of food by acarbose and Plantago psyllium mucilage. Arch Med Res 1998;29:137-41.
9. Florholmen J, Arvidsson-Lenner R, Jorde R, Burhol PG. The effect of Metamucil on postprandial blood glucose and plasma gastric inhibitory peptide in insulin-dependent diabetics (abstract). Acta Med Scand 1982;212:237-9.
10. Uribe M, Dibildox M, Malpica S, et al. Beneficial effect of vegetable protein diet supplemented with psyllium plantago in patients with hepatic encephalopathy and diabetes mellitus (abstract). Gastroenterology 1985;88:901-7.
11. Jarjis HA, Blackburn NA, Redfern JS, Read NW. The effect of ispaghula (Fybogel and Metamucil) and guar gum on glucose tolerance in man. Br J Nutr 1984;51:371-8.
12. Washington N, Harris M, Mussellwhite A, Spiller RC. Moderation of lactulose-induced diarrhea by psyllium: effects on motility and fermentation. Am J Clin Nutr 1998;67:317-21.
13. Eherer AJ, Santa Ana CA, Porter J, Fordtran JS. Effect of psyllium, calcium polycarbophil, and wheat bran on secretory diarrhea induced by phenolphthalein. Gastroenterology 1993;104:1007-12.
14. Burke V, Hodgson JM, Beilin LJ, et al. Dietary protein and soluble fiber reduce ambulatory blood pressure in treated hypertensives. Hypertension 2001;38:821-6.
15. Misra SP, Thorat VK, Sachdev GK, Anand BS. Long-term treatment of irritable bowel syndrome: results of a randomized controlled trial. QJ Med 1989:73:931-9.
16. Hallert C, Kaldma M, Petersson BG. Ispaghula husk may relieve gastrointestinal symptoms in ulcerative colitis in remission. Scand J Gastroenterol 1991;26:747-50.
17. Schaller DR. Anaphylactic reaction to “Heartwise.” N Engl J Med 1990;323:1073.
18. Fernandez R, Phillips SF. Components of fiber bind iron in vitro. Am J Clin Nutr 1982;35:100-6.
19. Roe DA, Kalkwarf H, Stevens J. Effect of fiber supplements on the apparent absorption of pharmacological doses of riboflavin. J Am Diet Assoc 1988;88:211-3.
20. Agha FP, et al. Giant colonic bezoar: a medication bezoar due to psyllium seed husks. Am J Gastroenterol 1984;79:319-21.
21. Covington TR, et al. Handbook of Nonprescription Drugs. 11th ed. Washington, DC: Am Pharmaceutical Assn, 1996.