Homocysteine and methionine are key amino acids with a vital connection to glutathione one of your body's most important substances! Methionine is abundant in many foods, so protein isn't the culprit, Methionine dietary supplementation potentiates ionizing radiation induced gastrointestinal syndrome American Journal of Physiology Gastrointestinal and Liver Physiology American Physiological Society Beyond Good and Evil The Weston A. Price Foundation The use of antioxidants in liver disease by James Kyffin British Veterinary Nursing AssociationBritish Veterinary Nursing Association Glutathione You Are The Healer Effect of multi nutrient insufficiency on markers of one carbon metabolism in young women: response to a methionine load European Journal of Clinical Nutrition