I suffered from diarrhea for about 7 years as a result of anit-biotic use and poor diet. My GI ran many tests, including a colonoscopy and prescribed a diuretic and muscle relaxant: big deal.
I started taking 2 very effective probiotic formulas before meals for months and found relief, as well as drinking kefir. I would still on occasion get diarrhea and knew something was missing in finding a cure. Btw, imo the best and most effective probiotic formula is Complete Probiotics from Dr. Mercola at Mercola.com. It only has two types of bacteria and a small amount, but is still somehow extremely effective.
Anyway, I began strength training and began taking whey protein, creatine, and glutamine (5grams). After a couple days I noticed my digestive system felt more "relaxed". As I continued taking the supplements I found I could eat anything and not get diarrhea. I decided to check to see if any of these supplements were the reason behind my "cure" and discovered that glutamine is known to repair the integrity of the intestinal lining.
Regarding Crohn's, I have communicated with someone in the UK who is involved in developing a vaccine for Crohns. The latest research indicates that Crohn's is caused by microbacteria (MAP), mycoplasms, cell wall defecient bacteria, etc. These are smaller and irregular forms of bacteria that go undetected in the typical pathology reports. The "Crohn's gene" simply means the individual has a lower immune response to these bacteria, which everyone is exposed to but only some get. He is going to see if glutamine can reduce penetration of this bacteria in the intestines. If you read other data about glutamine and the intestines, you will find it has been shown to do exactly this with other bacteria, as well as "heal" the intestinal lining.
In my opinion, if you satisfactorily replenish your flora with diverse bacteria, AND take supplemental glutamine, you will be very happy. BTW, it is not necessary to take it everyday, even if you eat something disagreeable, your intestines can handle it.