Epsom Salts or magnesium sulphate has a very unique affect when it is taken on an empty stomach. It the right concentration it actually causes the gallbladder to contract up to 65% by volume. Consequently the gallbladder has emptied and filled twice even before you take the olive oil and lemon/grapefruit juice. Magnesium sulphate purges the stomach, increases the wave like contraction in the bowel and performs a laxative action by drawing water into the bowel. I have written a short article about Epsom Salts on my blog //www.curezone.org/blogs/fm.asp?i=985355
The most common alternative laxative used is magnesium citrate.
Magnesium oxide is often taken if you are not getting enough magnesium from your
food or if there is a problem with how well your stomach absorbs it.
Magnesium oxide is sometimes also used as an antacid to help reduce acid amounts in your stomach. Magnesium oxide can be used as a quick acting laxative usually in special circumstances. It should not be used routinely as a laxative.