What is a Laxative, and what types are there?

First I'll give you some definitions:
Laxative: (lak's?-tiv) n. A food or drug that stimulates evacuation of the bowels. adj. Stimulating evacuation of the bowels. Causing looseness or relaxation, especially of the bowels.

Constipation: con·sti·pa·tion (kon'st?-pa'sh?n) n. Difficult, incomplete, or infrequent evacuation of dry hardened feces from the bowels. Obstruction; stultification.

   It is very obvious that by definition there is a very specific action that is required before a food or drug can be considered to be a laxative. There are several different kinds of laxatives on the market today. Some of them are chemically based, such as drugs, both over the counter (OTC) and prescription, and others are in food groups such as dried fruits or herbs. Laxatives can also be grouped by mechanism of action.

Saline cathartics, include dibasic sodium phosphate, magnesium citrate, magnesium hydroxide, magnesium sulfate, sodium biphosphate, and others. They act by attracting and holding water in the intestinal lumen, and may produce a watery stool. Magnesium sulfate is the most potent in this group. The Hyperosmotic laxatives are either glycerin or lactulose. They both act by holding water within the intestine. Lactulose may also increase peristaltic action of the intestine. A Docusate, is the only real stool softener. It holds water in the fecal mass, creating a larger, softer stool. The issue here is that docusates have no effect on constipation since it must be present in the digestive tract before the fecal mass forms to have any effect. It may, however, be useful for prevention of recurrent constipation or for those who are about to take a constipating drug, such as narcotic analgesics. A Stimulant, laxative increases the peristaltic movement of the intestine. Some examples are Cascara Sagrada and Bisadocyl. Castor oil also works in a similar fashion. Peristaltic movement is the rhythmic contraction of the peristaltic muscles which surround the intestine. The rhythmic contractions move the food through the digestive tract, through the colon and out of the bowel. Bulk producing laxatives or fiber increase the volume of the stool, and will both soften the stool and increase motility. Psyllium and methylcellulose are examples of this type. The overall effect is similar to that of eating high fiber foods, this class and the stimulant class,(in moderation) of laxatives are the most suitable for regular use.
   The two types of laxatives that I listed last are STIMULANTS and BULK PRODUCING LAXATIVES. I listed them last because I feel that it is a combination of these two categories that produce the best results with the fewest adverse side effects. I favor those two categories for several reasons... First, these are the ONLY types of laxatives that don't use the retention of water as the mechanism or vehicle to accomplish the task at hand. This is very important to those individuals that are trying to shed a few pounds. It is also important to note that the bloated feeling that sometimes comes with taking a laxative is the water that is being held in the bowel. Second, a comfortable bowel movement isn't the only goal for a good laxative. A good laxative should not only help with comfortable elimination but it should cleanse the colon walls and help promote and restore the proper function of your colon. Over the years our colons have to endure all of the junk food and constipating prescription drugs that we consume. It is fair to assume that there will be a certain amount of build-up on the colon walls. That build-up then prevents the colon from performing at its best. This makes it imperative that a laxative acts in two ways; first to help with comfortable and regular bowel movements and second it must clean the hardened plaque filled feces off of the colon wall. This prevents fecal matter build-up from being the center of future health related issues. Finally and equally as important when properly formulated and properly used both the BULK PRODUCING and the STIMULANTS are best suited for regular use.