Glutathione is widely found in animals and plants and plays an important role in living organisms. Relatively high levels of glutathione are found in fresh meat, 20 mg/100g in beef, 9.5 mg/100g in chicken breast (with skin), moderate in fruits and vegetables, while dairy products, grains and lower glutathione concentrations in bread. Since glutathione is synthesized intracellularly and transported outside the cell, glutathione levels appear to be higher in tissues than in blood. For example, glutathione in sheep liver tissue is 1200 to 2200 mg/kg, glutathione in muscle tissue is 180 to 540 mg/kg, and glutathione in whole blood is 170 to 250 mg/L . Among tissues, the liver has the highest concentration of glutathione, followed by the kidneys, lungs, intestines, brain, and then muscle (heart). Studies of glutathione levels in mice have shown that changes in glutathione in the liver, kidneys, heart, spleen and brain are parallel to those in whole blood, so blood levels can be used as an overall physical indicator.
Boosting tissue antioxidant capacity with foods containing high concentrations of glutathione or cysteine and glutamate may be an option to prevent and/or treat disease.