Psyllium husk is a common, high-fiber laxative made from the seeds of a shrub. It's also used to treat a number of conditions, such as high cholesterol and colon cancer, which may benefit from a high-fiber diet; however, some of these uses do not have proven benefits. Psyllium does cause some serious side effects, so talk to your doctor before taking it.
Psyllium has been proven to relieve constipation, according to the University of Maryland Medical Center, or UMMC. When it comes into contact with water, psyllium swells into a gelatinous mass that pushes stool through the digestive tract. This same process also makes it useful to treat mild to moderate diarrhea, because psyllium soaks up excess water from the digestive tract, which hardens diarrhea and makes it slower to pass. Laxatives like psyllium can be helpful if you have hemorrhoids. However, studies have shown mixed results for people with irritable bowel syndrome or inflammatory bowel diseases like ulcerative colitis or Crohn's disease. If you have any of these diseases, consult your doctor before using psyllium.
Soluble fiber, the type contained in psyllium, can help lower cholesterol, according to the UMMC. Psyllium appears to lower both total cholesterol as well as LDL or bad cholesterol, which might reduce the risk of heart disease. When combined with a low-fat diet or cholesterol-lowering drugs, psyllium appears to boost the benefit of either of these approaches to lowering cholesterol.
Because it is a good source of fiber, psyllium is used for a number of other conditions for which there is not enough scientific evidence to know whether it really works or not, according to the UMMC. In general, though, nutritionists agree that it is better to get fiber from whole grains, fruits and vegetables, which contain a host of other helpful nutrients, than it is to take a supplement, according to the American Cancer Society. After some early and optimistic studies, many people began taking psyllium to protect against colon cancer. But more recent, better-designed research has found little benefit to this. Other unproven uses of psyllium are as treatments for diabetes, high blood pressure and obesity.