High-quality whey or soy protein (cold-pressed whey protein derived from grass-fed cows or soy protein derived from fermented soy, and free of hormones, chemicals and sugar) provides all the key amino acids for glutathione production (cysteine, glycine and glutamate) and contains a unique cysteine residue (glutamylcysteine) that is highly bioactive in its affinity for converting to glutathione.