Phenylketonuria (PKU) is a rare genetic disease caused by the inability of the body to metabolize the essential amino acid, phenylalanine (Phe). Left untreated, Phe will accumulate in the blood and body tissues and this excess Phe is toxic to the central nervous system. Untreated PKU will often lead to mental retardation, seizures and other serious medical conditions. PKU disease is typically diagnosed at birth through newborn screening.
Standard treatment of PKU requires a strict, life long, adherence to a special diet, which is very low in phenylalanine. Because phenylalanine is present in almost all natural protein sources, the diet is extremely challenging for patients, requiring the elimination of foods that contain protein. Natural protein sources are replaced in the PKU patient with synthetic free amino acid protein substitutes called “metabolic formula” or they are often referred to as “medical foods”. These protein sources are consumed daily in place of natural proteins.
Glytactin is the world’s first PKU protein formula that is made from a natural whole protein derived from whey called glycomacropeptide (GMP). GMP is produced during the cheese making process and it is the only naturally occurring protein that does not contain Phe in its pure form. The natural absence of Phe in this unique protein makes it ideal for the PKU diet. Glytactin was developed in collaboration with the University of Wisconsin and is a combination of GMP and certain critical amino acids, such as arginine and tyrosine, which are also not found naturally in GMP. Until the introduction of Glytactin in 2010, PKU formulas were always made of 100% synthetic, man-made free amino acid proteins. Studies have shown that natural intact proteins, like GMP, have a slower absorption rate in the body and an improved protein usage when compared with single amino acids, which mimic whole intact protein. Further evidence also suggests that consuming GMP promotes satiety in PKU individuals when compared with an amino acids diet , while sensory studies in individuals with PKU find GMP-based medical foods more palatable and of improved variety than the amino acids diets. [1, 3, 4]