Glutathione is sometimes called the master antioxidant because it plays such an important role in cellular defence against free radicals. Glutathione is a substrate for the selenoprotein enzyme glutathione peroxidase, which catalyses the removal of hydrogen peroxide from the cytosol and mitochondria of cells. As well as its role in the removal of hydrogen peroxide, glutathione is also involved in the recycling of the antioxidants vitamin C and vitamin E. These vitamins are able to react with free radicals by donating an electron in a reduction reaction, and in the process become oxidised themselves. Glutathione reduces oxidised vitamin C and vitamin E, thus maintaining cellular levels of important antioxidants. Decreased cellular glutathione are associated with cell damage, depressed immunity and the progression of aging. Generally speaking, higher levels of glutathione are associated with improved health.
Supplements of glutathione are ineffective at raising glutathione levels because glutathione is a tripeptide made up of L-cysteine, L-glutamic acid, and glycine and the human gut is able to hydrolyse the peptide bonds during digestions. A number of foods and supplements are able to raise intracellular levels of glutathione, but perhaps the simplest and safest way is by supplementation with vitamin C. For example, a study published in the American Journal of Clinical Nutrition in 19931 demonstrated that supplementation with 500 mg of vitamin C as a tablet for two weeks increased red blood cell glutathione by 43 % compared to baseline values. The values detected in the subjects ranged from an 8 % increase to an 84 % increase in red blood cell glutathione concentration, but these values were not correlated with vitamin C plasma levels. Supplementation with 2000 mg of vitamin C did not significantly increase red blood cell glutathione above the 500 mg level.
Vitamin C appears to be a safe and effective way to increase cellular levels of the important antioxidant glutathione. The level of vitamin C used to attain this raised glutathione levels in this study are obtainable through the diet if foods rich in vitamin C are chosen. However, studies have reported large variations in the vitamin C content of foods, and storage and transport conditions can reduce the vitamin C content of fruits and vegetables. For this reason it is recommended to supplement with vitamin C tablets to ensure a reliable plasma concentration. Some manufactures charge much higher prices for their brands of vitamins C, but there is no real advantage to the consumer in buying premium brands of such a cheap, easily manufactured chemical. Most brands of vitamin C will therefore provide adequate protection.
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