The GMP-based diet contains more whole protein than the traditional PKU diet. A GMP-based diet provides approximately 70% of protein from whole protein (found in GMP-medical foods and food allowed on a diet for PKU) and approximately 30% of protein from synthetic amino acids. In contrast, traditional diet for PKU provides approximately 80% of protein from synthetic amino acids and 20% from food sources.
Not all GMP products are the same. Glytactin is a unique blend of GMP that is supplemented with specific amino acids to ensure a high quality protein. The types and amounts of amino acids added are based on clinical evidence1 and meet World Health Organization requirements for the proper ratio of the branched-chain amino acids, leucine and isoleucine.2 Since these amino acids share a degradative enzyme, an improper ratio can result in relative deficiency of one, which can impair protein synthesis. Glytactin with GMP has been shown to maintain plasma branched-chain amino acids in the normal range.3
Glytactin-based products are absorbed and utilized better than products made solely from amino acids. When a person consumes amino acids alone, the concentration of amino acids in the blood rises rapidly and then decreases rapidly, whereas if a person consumes whole protein the concentration of amino acids in the blood is slower to rise and stays higher for longer.4 This more stable concentration of amino acids in the blood enhances protein synthesis (building lean body mass), and may also be related to the greater satiety reported by subjects taking Glytactin.
A Glytactin-based diet improves nitrogen retention. In one study, subjects with PKU had significantly lower blood urea nitrogen (BUN) concentrations and significantly higher total amino acid concentrations after consuming a GMP-based meal as compared to an amino-acid based meal.1 A lower BUN means more nitrogen is being retained and a higher amino acid concentration means that the amino acids are not being oxidized rapidly and are available in the pool of amino acids needed for protein synthesis. Also, plasma albumin concentration was significantly higher with Glytactin in support of improved protein synthesis compared with the amino acid- based diet.3 Individuals with PKU consumed Glytactin-based medical food more often than they did amino acid-based medical food. Taking medical food throughout the day improves protein synthesis and stabilizes blood phenylalanine.5
In summary, Glytactin contains a unique blend of GMP plus amino acids that provides a safe, effective alternative to amino acid-based diets and enhances protein synthesis in individuals with PKU.
References: 1. van Calcar S et al. Am J Clin Nutr. 2009;1068-77. 2. World Health Organization Technical Report Series 935, 2007. 3. Ney D. et al. Am J Clin Nutr. 2016; 105: avail Aug 2106. 4. Gropper S. et al. JPEN 1991;15:48. 5. MacDonald A. et al. Arch Dis Child. 1996; 74:412.