Our ancestors ate whole animals. Skin, cartilage, tendons, bones, organs. That meant they consumed massive amounts of glycine from collagen rich tissues. Modern humans eat almost exclusively muscle meat, which is extremely high Re: does glutathione have more than2 peptide bonds? Glutathione for Food and Health Applications with Emphasis on Extraction, Identification, and Quantification Methods: A Review Dietary glycine supplementation enhances syntheses of creatine and glutathione by tissues of hybrid striped bass (Morone saxatilis Morone chrysops ) fed soybean meal based diets Journal of Animal Science and Glycine supplementation can partially restore oxidative stress associated glutathione deficiency in ageing cats British Journal of Nutrition Cambridge Core