Clinical trials have shown that Senna increases the frequency of bowel movements and is effective as a laxative for occasional constipation. It also provides quick relief, working in 8-10 hours. There are several types of laxatives: bulk-forming (which add bulk to stool), hyperosmotics (which increase the amount of water in the bowels), lubricants (which coat the bowel) and stimulants, which act directly on the intestinal wall. Senna is both a stimulant and hyperosmotic laxative. Senna leaf anthranoids have been documented to stimulate peristaltic contractions, helping move waste through the GI tract. In addition, they increase levels of water and electrolytes in the intestines, softening stool and accelerate colonic transit time, increasing the frequency of bowel movements.