Celiac disease is defined as “small bowel mucosal damage, which is reversible on a gluten free diet, in genetically predisposed people (who carrying the DQ2/DQ8 HLA gene)”.
Gluten can trigger your body’s immune response that can then go onto cause this tissue gut damage. However, this damage is slowly progressive: the longer you have been eating gluten, the worse the damage. Of course, when you have this gluten-gut-damage, you do not absorb your food nutrients very well, and this leads to many other health problems. But, with any on-going gluten ingestion, the gut damage is perpetuated.
Will my gut (bowel) recover from celiac?
The good news is that as soon as gluten is (completely) removed from your diet (gluten zero), the bowel at last has a chance to recover. In children, who have had a shorter time of gluten exposure, their bowel usually recovers very quickly (within weeks their symptoms go away, and within months their gut is completely normal). It is rare for a child to not have complete gut recovery.
The bad news is that as we get older, and have had this gluten assault for a lot longer, our gut damage can be more severe and more extensive. Consequently, you can take a lot longer to get better. You might take weeks and months to begin to feel better and sometimes it takes years for the gut to fully restore to normal. Of course, if you still eat small amounts of gluten, or your diet is not scrupulously purged of gluten, then this small amount of gluten-toxicity can keep causing you ongoing damage to your gut (and other organs, especially nerves and brain).
To check if your gut has properly healed, you can either have second endoscopy (which is often scheduled about a year after you have started a gluten free diet), or you can see whether or not the tissue-damage-markers (tTG, DGP, and EMA) are coming down. There is a good correlation between blood test results and endoscopy.
The lesson from this: diagnose celiac disease as early as possible, and once diagnosed remain strictly gluten-zero, without exception, lifelong. If you have ongoing gut disease and ongoing symptoms, there may be other things going on and you may need to have other strategies to help gut healing.