L-glutathione

L-glutathione is a peptide (small protein) composed of three amino acids: cysteine, glutamic acid, and glycine.
Dietary glutathione is found in fresh and frozen fruits and vegetables, fish, and meat. Asparagus, avocado, and walnuts are particularly rich dietary sources of glutathione.
A deficiency in glutathione can be the result of diseases that increase the need for glutathione, deficiencies of the amino acids needed for synthesis, or diseases that inhibit glutathione formation. Examples of some health conditions that are associated with glutathione deficiency include diabetes, low sperm counts, liver disease, cataracts, and HIV infection, respiratory distress syndrome, cancer, and pulmonary fibrosis. Cigarette smoking is also associated with low glutathione levels because it increases the rate of utilization of glutathione (L-glutathione is used as an antioxidant to remove the free radicals produced by the smoke).
People who have a proven glutathione deficiency, which may require administration of glutathione intravenously, intramuscularly, or by aerosol, should be treated by a healthcare professional. All ovarian cancer patients currently taking cisplatin (Platinol®) should discuss using intravenous glutathione with a healthcare professional.
L-glutathione taken orally has no known side-effects or interactions.
L-glutathione interacts with chemotherapy drugs; anyone on chemotherapy for cancer should only take L-glutathione on advice of a physician, preferably an oncologist In any case, if your doctor decides that you need L-glutathione it will need to be administered by some form of injection or by aerosol - in the quantities needed in that case, it will not be absorbed if taken orally.
L-glutathione also has another effect. All sulphur-containing amino acids are strong chelating agents; which means that they bind to various metals. This means that L-glutathione would be useful to remove heavy metals such as lead and mercury from the body; however, there are other, much cheaper, supplements (such as garlic and L-cysteine) that would also do this job