Glytactin® Build 20/20smooth is a glycomacropeptide (GMP) based-protein powdered medical food for the dietary management of PKU for those on a low phenylalanine diet who are seeking fewer calories, lower volume, and lower Phe than other GMP-based PKU medical foods. 20 mg Phe. Mixes with 4 oz water. 'Natural protein – GMP plus naturally fermented amino acids. Nutritionally complete with vitamins and minerals. Contains DHA to support brain and heart health. Contains probiotics to support digestive health. No artificial colors or flavors. Always use Glytactin BUILD 20/20 Smooth as directed by your physician or dietitian.