Reduced glutathione, commonly referred to as glutathione or GSH, is a tripeptide composed of L-glutamine, L-cysteine, and glycine. It is ubiquitous in living systems. Glutathione biosynthesis can be affected by individual and/or dietary biochemical factors. Chronic oxidative stress can also deplete cellular glutathione. Glutathione precursors, such as whey protein, vitamin C, and glutamine, are often recommended to increase glutathione levels in the body; however, results are not uniform. Biological individuality is such that not every organism has the same capacity to metabolize the precursor to increase glutathione.