zucchini,
L-Glutamine is known to help with colonic repair. That's the reason I take it. But you'll need to take quite a bit of it - 2 or 3 capsules won't do it. I take about 15 grams of powder and mix it in with my protein whey shakes at least twice a day. I get mine from here: http://www.nutrabio.com/Products/glutamine1.htm - I've found it to be the best quality and cheapest as well.
Yes, as was mentioned before, for colonic repair it should be taken on empty stomach.
Just one word of caution: since it is an amino acid, you have to be very careful how you mix it, if you use those high powered blenders it will pulvarize the amino acids. So it's important to mix carefully, with a very low speed blender or as I do it, by hand with a spoon.
Also, please note that there is a big difference between L-Glutamine and Glutamic Acid.
You could try it and see how you fare on it?