Here is a brief review on tryptophan, one of the 9 amino acids essential to the good functioning of the body.

Its effects on depression, sleep and appetite regulation have been well known for a long time. More recently, it proved to have a role in immunity and some studies have demonstrated the effects of tryptophan metabolites in autoimmune diseases such as multiple sclerosis and rheumatoid arthritis. In short, Tryptophan helps regulate the inflammatory states.

This amino acid cannot be produced by the body but needs to be brought by the daily diet and is found in large quantities in proteins.

However, it was found that some gut bacteria could alter the tryptophan bioavailability. These ” Tryptophan positive ” bacteria metabolize tryptophan, making it less available to the body and compromising its work on the immune cells.

source: http://www.sciencedirect.com/science/article/pii/S1043661814001704