Many people take psyllium as a fiber supplement for its laxative effect or as a way to help lower blood cholesterol. Made from the husks of seeds from the Plantago ovata plant, it is sold as a powder or capsules.
Another potential benefit of psyllium is its ability to help control blood sugar in people with type 2 diabetes. This was examined in an analysis of 10 studies, published in the American Journal of Clinical Nutrition. Psyllium was taken before meals at standard doses. The greatest reductions in blood sugar and hemoglobin A1c (a longer-term measure of blood sugar control) occurred in people with the worst blood sugar control initially and were “comparable to the effect of many drugs that are used to treat diabetes,” the researchers wrote. The analysis also looked at 14 studies involving people with prediabetes and found that psyllium modestly reduced blood sugar in them.
If you have diabetes and take medication for it, consult your health care provider before trying psyllium, since the combination may result in excessive lowering of blood sugar; your dose of medication or psyllium may need to be adjusted. And make sure the psyllium doesn’t contain added sugar (it often does). The authors of the study were employed or funded by Procter & Gamble, the maker of a brand of psyllium (Metamucil).
How psyllium works
The fiber in psyllium absorbs water in the colon, resulting in bulkier stool (thus it’s called a “bulk-forming” laxative); it also forms emollient gels that facilitate the passage of stool. Psyllium is gentle and usually takes 12 to 24 hours to affect bowel movements. Its cholesterol-lowering effect was perhaps best seen in a 2005 study in the Archives of Internal Medicine, which found that people who took psyllium three times a day with meals, plus a low-dose statin drug, for 12 weeks lowered their elevated LDL by an extra 15 percent, compared to those just taking the statin.
In some people psyllium causes bloating, gas, diarrhea, or (if they don’t drink enough fluid) constipation. And some are allergic to it. Psyllium can interfere with certain drugs, so if you’re on medication, ask your pharmacist. You may have to take the drug either at least one hour before or two hours after the psyllium.
Also see Psyllium Fiber Supplements 101.