The body uses proline to make proteins, such as collagen. Collagen is found in the skin, bones, and joints. Proline is also involved in the general function of cells.Proline is unique in that it is the only amino acid where the side chain is connected to the protein backbone twice, forming a five-membered nitrogen-containing ring. ... For this reason, Proline can often be found in very tight turns in protein structures

 Functions of proline include helping form collagen, regenerating cartilage, forming connective tissue, repairing skin damage and wounds, healing the gut lining, and repairing joints.

Supplementation with proline but not glutamic acid resulted in a linear increase (P . 01) in weight gain. The failure to obtain a significant proline X glutamic acid interaction indicates that the response to proline was independent of the level of supplementary glutamic acid.

Proline is LIKELY SAFE when taken by mouth in food amounts. There isn't enough reliable information to know if proline is safe when used in larger amounts as medicine or what the side effects might be.

D PROLINE