Psyllium , or ispaghula , is the common name used for several members of the plant genus Plantago whose seeds are used commercially for the production of mucilage. Psyllium is mainly used as a dietary fiber to relieve symptoms of both constipation and mild diarrhea, and occasionally as a food thickener. Allergy to psyllium is common in workers frequently exposed to the substance. Use of psyllium in the diet for three weeks or longer often lowers blood cholesterol levels in people with elevated cholesterol, and can lower blood glucose levels in people with type 2 diabetes. Use of psyllium for a month or longer may produce a small reduction in systolic blood pressure.The plants from which the seeds are extracted tolerate dry and cool climates and are mainly cultivated in northern India. Uses
Dietary supplements containing psyllium are sold mainly to aid weight loss, although there is little scientific evidence for such effects. Food
Psyllium has been used as a thickener in ice cream and other frozen desserts. A 1.5% weight/volume ratio of psyllium mucilage exhibits binding properties that are superior to a 10% weight/volume ratio of starch mucilage. The viscosity of psyllium mucilage dispersions are relatively unaffected between temperatures of 20 and 50 °C (68 and 122 °F), by pH from 2 to 10, and by salt (sodium chloride) concentrations up to 0.15 M.

Human health
Constipation
Psyllium is mainly used as a viscous, soluble dietary fiber that is not absorbed by the small intestine.
The purely mechanical action of psyllium mucilage is to absorb excess water while stimulating normal bowel elimination. Although its main use has been as a laxative, it is more accurately regarded as a dietary fiber and as such can help reduce the symptoms of both constipation and mild diarrhea. The laxative properties of psyllium are attributed to the fiber: it absorbs water and subsequently softens the stool. It increases flatulence (gas) to some degree. High blood cholesterol
In 1998, the U.S. Food and Drug Administration approved a health claim on food labels for dietary psyllium as a soluble fiber – if consumed regularly – that would reduce the risk of heart disease by lowering blood cholesterol. Clinical research demonstrated that seven grams or more per day of soluble fiber from psyllium seed husk would sufficiently lower total cholesterol and low density lipoprotein cholesterol in people with hypercholesterolemia, two accepted biomarkers for risk of coronary heart disease. The findings were later confirmed in a meta-analysis that incorporated more evidence. To be eligible for the FDA-allowed health claim, one serving of a manufactured food or dietary supplement must contain at least 1.7 g of psyllium as soluble fiber. Whole oats, barley and foods containing beta-glucan soluble fiber were included as eligible sources for the label claim.