The extensive surface area of our digestive system enables us to extract all of the essential nutrients from our diet. The intestinal tract, with its extensive blood supply, has a remarkable ability to renew the epithelial cell lining every 4-5 days . This rapid turnover of cells makes our digestive system particularly susceptible to injury due to the relatively high concentration of free radicals and reactive oxygen species (ROS) which are produced by our normal metabolism. Beyond this, toxins in the food we eat can cause further injury. Nitrosamines from processed meat and other heavy metals such as mercury are just a few examples of toxins we may ingest .
Our digestive system has evolved a complex biochemistry to counter these adverse conditions and glutathione is of major importance in this defense mechanism. The mucosal lining of the intestinal tract is rich in glutathione and it has been suggested that it plays a vital role in gut barrier function. However, as we age, or with the progression of persistent health issues, glutathione levels may be less than optimal for maintaining good health.
Many gastrointestinal (GI) diseases have been associated with glutathione deficiency. These include inflammatory bowel disease [3, 4], ulcerative colitis  Crohn’s disease [6, 7] and Celiac disease . An exaggerated inflammatory response is also implicated during the development of many gastrointestinal diseases and this is further exacerbated by depleted glutathione levels.
Many GI disease researchers have suggested that increasing glutathione levels could be particularly useful. However, only NAC and glutathione itself have been readily available for experimentation and these have repeatedly failed to demonstrate bioavailability to increase cellular glutathione levels above homeostasis.
Supplementation with Glyteine is different. In a human clinical trial, a marked increase in glutathione levels was seen regardless of its initial (basal) concentration. And, most importantly, this increase occurred rapidly (within hours) . With other supplements, a slight increase in glutathione could only be observed after many months.