Keep in mind that l-glutamine is not an herb, it's an essential amino acid. You can get it a whole bunch of different ways. But I take it daily as a powder. It helps to heal the epithelial cells lining your digestive system. Aloe juice does almost the same thing (like aloe on a burn to speed healing), but also acts as a laxative. Not the best for a lot of us. L-glutamine will help your muscles bounce back if you are training, as well.
As for the GI insinuating herbals are a waste of money, keep in mind that these specialists are slicers and druggists. They work in the realm of chemistry, surgery and pharmacy, yet many have not taken more than one nutrition course. My GI actually told me that my diet didn't matter, after I expressed how sick drinking coffee makes me. Sick for weeks! His response, drink coffee and just take your meds. These people are experts at what they have studied, and they have not studied nutrition and herbals.
What? Oh, that's right. Med school has nothing to do with nutrition, or how to manage chronic disease. So just keep in mind that some things you will need to test out yourself. I have had a tremendous amount of success with supplements, when extraordinarily expensive drugs from pharmacy companies didn't work and only made me much sicker.
But that is a hard sell for many western doctors. If you're still having concerns, don't be afraid to visit a TCM or Ayurvedic medical practitioner. There are forms of medicine which have been around for a lot longer than 100 years - which is about as long as our modern surgery has had to become this science that we now all believe in no matter what. Except that it doesn't always work, and then we get "experts" sneering at other options.
I think that the more we can do with diet and prevention, the better!