Clinical Application and Mechanism of Action
The laxative properties of Psyllium are due to the ability of the mucilage portion of the seed husk to absorb water, in a similar fashion as a sponge. This swelling creates a large gelatinous mass that applies pressure to the bowel wall and thereby, stimulates more frequent contractions of the muscles that rhythmically contract to propel fecal matter through the large intestine. Due to the high water content of this gelatinous fecal mass, the developing fecal matter is softened, and hydrated, provided sufficient water is ingested to allow this to occur. Thus, as a bulk-forming laxative, Psyllium supplementation encourages more rapid movement of fecal contents through the large bowel, softens the stool for easier elimination, and by absorbing water it may help to dilute the effects of bowel carcinogens; a means proposed to reduce risk of colon and rectal cancers. 3,6
Studies show that Psyllium is highly effective in relieving lifestyle-related and functional constipation, but not in cases caused by diseases of the intestinal tract. 7
In functional cases, Psyllium has been shown to be better than, or at least as effective as, standard laxative medications (e.g., docusate sodium). Psyllium also has fewer side effects than most other laxative medications and offers better stool consistency. 6
Psyllium has been used successfully to control diarrhea due to its ability to increase the thickness of stools. 8,9 This also has important application for HIV patients, taking Protease Inhibitor drugs, which commonly produce diarrhea and thereby further contribute to malnutrition, weight loss, and immunosuppression, often seen in these patients. Psyllium is one of the interventions that is shown to reduce diarrhea in these patients.
3. High Cholesterol
Based upon substantial clinical and scientific evidence, the United States Food and Drug Administration (FDA) has approved a health claim for Psyllium in regards to its ability to reduce cardiovascular disease risk. 4 This is primarily attributable to the ability of the soluble fiber fraction of Psyllium seed husk to drag cholesterol and bile acids (bile acids may otherwise be re-absorbed and converted into cholesterol within the liver) through the intestinal tract and eliminate them from the body in the stool. 4,11 It may also stimulate the liver to convert cholesterol to bile acids, lowering the total cholesterol load on the body. 11,13 Through these mechanisms, Psyllium supplementation has been shown to reduce blood cholesterol levels to a modest degree in patients with high cholesterol and in patients whose cholesterol levels fall within the normal range. Numerous double-blind studies have shown that Psyllium supplementation can lower total cholesterol and LDL-cholesterol (bad cholesterol), with no significant effect on HDL-cholesterol levels (good cholesterol). 12,14 Studies involving children have also shown a significant cholesterol lowering effect in subjects with elevated cholesterol levels. 15
In the Lipid Assessment Treatment Project (L-TAP), the success rates for lipid-regulating therapies and treatments according to the National Cholesterol Education Program (NCEP) Adult Treatment Panel II (ATP II) were reported to be a 43% reduction in LDL-cholesterol for bile acid sequestrant drugs, 39% for high-dose niacin, 32% for gemfibrozil, 28% for Psyllium fiber, 40% for statin drugs (e.g., lovastatin), and 40% for combination therapies. 25
A meta-analysis conducted to evaluate the hypolipidemic effects of Psyllium fiber (which pooled eight controlled studies, involving 384 and 272 subjects with mild to moderate hypercholesterolemia receiving Psyllium or cellulose placebo, respectively), revealed that Psyllium supplementation (10.2 gm per day), as an adjunct to a low fat diet, lowered total cholesterol by 4%, LDL-cholesterol by 7% and the ratio of apolipoprotein (apo) B to apo A-1 by 6%, relative to the placebo. The researchers concluded that Psyllium is well tolerated and safe when used as an adjunct to a low-fat diet in individuals with mild-to-moderate hypercholesterolemia. 26
A study involving 34 hypercholesterolemic men with type II diabetes showed that men receiving 5.1 gm of Psyllium 20-30 minutes prior to breakfast and evening meals for eight weeks, reduced their total cholesterol levels on average by 8.9% and LDL-cholesterol levels by 13%, compared to the placebo group. As well, their post-lunch glucose levels dropped by 4.2%, compared with a 12.7% increase in the placebo group.
4. Diabetics and Blood Sugar
The soluble portion of Psyllium has been shown to improve blood glucose regulation in both insulin-dependent and non-insulin dependent diabetic patients. 16,17,18 Soluble fiber is known to slow the absorption of simple sugars (monosaccharides) from the intestinal tract, helping to prevent a hyperglycemic response following a meal containing carbohydrate foods. Challenge studies have shown that Psyllium supplementation can significantly lower the glycemic response to a carbohydrate test meal in these patients, producing lower, more controlled blood glucose levels, postprandially. 12
5. Ulcerative Colitis
A double-blind trial involving patients with ulcerative colitis showed that Psyllium supplementation significantly reduced symptoms such as bleeding, and helped patients remain in remission longer (upon ingesting 20 gm of ground Psyllium seeds, twice daily with water), compared to the use of the medication mesalamine alone. However, the combined effects of mesalamine and Psyllium produced the best overall outcomes in this study. 19
6. Irritable Bowel Syndrome (IBS)
Some studies suggest that Psyllium supplementation may be helpful in the management of IBS. An illuminating study by J. Holtz, et al, showed that both Psyllium and wheat bran supplementation improved stool frequency and consistency in a 6-week trial of thirty IBS patients. However, the Psyllium group demonstrated superior outcomes with respect to stool frequency and degree of abdominal distension, making it the preferred intervention, according to the researchers involved in this trial. 20 As there are few effective interventions in the treatment of IBS, it is worth noting that well-designed trials support the use of Psyllium supplementation in these cases, although outcomes may vary greatly from patient to patient.
7. Blood Pressure
There is some evidence to suggest that Psyllium supplementation can help reduce high blood pressure by enhancing the fecal excretion of sodium absorbed in the intestinal tract. Although this evidence comes mostly from animal studies, a trial involving sixty-eight hypercholesterolemic patients demonstrated a small reduction in blood pressure in patients receiving 8 gm of Psyllium supplementation each day for four weeks. Their cholesterol levels were also reduced, providing a desirable synergistic effect in reducing cardiovascular disease risk.