Inborn errors of metabolism

Inborn errors of metabolism

Inborn errors of metabolism

Developing safe and effective proteins for PKU nutrition

Phenylketonuria (PKU) is what is known as an inborn error of metabolism – a rare genetic disorder that affects one in 10,000 to 15,000 people. Patients with PKU are unable to metabolise the amino acid phenylalanine (phe), which is naturally present in all proteins.

If PKU patients consume a diet with a normal protein level, phe will accumulate in their blood and brain at toxic levels. If left untreated, high levels of phe can cause brain damage and mental retardation in PKU infants and children1.

Challenges of PKU nutrition

It is therefore crucial that PKU patients follow a restrictive, low-protein diet to keep phe levels within a healthy range. The PKU diet is based on low-protein foods combined with protein substitutes, which consist of artificial free amino acids devoid of phe. These free amino acid formulas often have an offensive taste and smell.

Some patients experience problems with bad breath, most likely due to the sulphur-containing free amino acids in the formulas, which are converted into foul-smelling volatile sulphur compounds by oral bacteria. These issues, combined with the challenges of social acceptance when following the diet, cause significant patient non-adherence to the PKU diet, especially during the teenage years2.

The off-taste and smell of the amino acid formulas are the source of another problem, too – that some patients choose to drink their formula just once a day instead of in three or more doses as recommended. This has the potential to lower protein utilisation, nutritional status and control of phe levels, as well as increase hunger sensations during the day3.

Better nutritional options with whey

Arla Foods Ingredients has collaborated with leading experts for more than a decade to develop better nutritional options for PKU patients. The focus is Lacprodan®CGMP-20 – our whey-derived, highly purified casein glycomacropeptide (CGMP) product.  Lacprodan®CGMP-20 is a suitable protein source for PKU patients due to its very low content of phe. In foods for PKU nutrition, it can replace a large share of the free amino acids and provide several nutritional benefits.

It is essential that we continue to build up scientific evidence and discover the full health benefits of CGMP in PKU nutrition. At Arla Foods Ingredients, we have a team of dedicated nutrition scientists who collaborate closely with universities and research partners to find the most suitable protein sources for PKU patients. We also welcome collaborations with our customers to document the health benefits of CGMP and develop further high-quality and effective foods for PKU diets.


  1. Blau N, Van Spronsen FJ, Levy HL. Phenylketonuria. Lancet. 2010;376(9750):1417-1427. doi:10.1016/S0140-6736(10)60961-0.
  2. van Calcar SC, Ney DM. Food products made with glycomacropeptide, a low-phenylalanine whey protein, provide a new alternative to amino Acid-based medical foods for nutrition management of phenylketonuria. J Acad Nutr Diet. 2012;112(8):1201-1210. doi:10.1016/j.jand.2012.05.004.
  3. MacDonald A, Rylance G, Davies P, Asplin D, Hall SK, Booth IW. Administration of protein substitute and quality of control in phenylketonuria: A randomized study. J Inherit Metab Dis. 2003;26(4):319-326. doi:10.1023/A:1025186217369.
  4. Calcar S van, MacLeod E. Improved nutritional management of phenylketonuria by using a diet containing glycomacropeptide compared with amino acids. Am J …. 2009. doi:10.3945/ajcn.2008.27280.1.
  5. Ney DM, Stroup BM, Clayton MK, et al. Glycomacropeptide for nutritional management of phenylketonuria: a randomized, controlled, crossover trial. Am J Clin Nutr. 2016:334-345. doi:10.3945/ajcn.116.135293.
  6. Zaki OK, El-Wakeel L, Ebeid Y, et al. The Use of Glycomacropeptide in Dietary Management of Phenylketonuria. J Nutr Metab. 2016;2016(2008). doi:10.1155/2016/2453027.
  7. Lim K, Calcar S van, Nelson K. Acceptable low-phenylalanine foods and beverages can be made with glycomacropeptide from cheese whey for individuals with PKU. Mol Genet …. 2007. Accessed February 4, 2015.
  8. MacLeod EL, Clayton MK, van Calcar SC, Ney DM. Breakfast with glycomacropeptide compared with amino acids suppresses plasma ghrelin levels in individuals with phenylketonuria. Mol Genet Metab. 2010;100(4):303-308. doi:10.1016/j.ymgme.2010.04.003.
Casein glycomacropeptide

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Lacprodan® CGMP-20

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