Non-protein nitrogen in dairy ingredients: A closer look at its contribution in infant nutritional product formulation

As the non-protein nitrogen (NPN) fraction of milk, and its components, do not directly contribute to protein synthesis, historically, it was considered to have little biological, nutritional, or economical value. Recently, there has been an increased emphasis on NPN components and their association with health benefits. While the NPN fraction has previously been perceived neutrally, or indeed sometimes negatively, recent studies suggest that the fraction is undervalued or misunderstood, particularly regarding infant growth and development, highlighting the need for a comprehensive understanding of the NPN components in infant formula (IF) and the dairy ingredients most used in its formulation. This study focuses on the identification and quantification of NPN components in selected dairy ingredients and emphasizes the importance of considering NPN during the formulation of IF. Some findings to note are that whole milk powder was a significant source of uric acid, while alpha-lactalbumin enriched whey had the highest concentration of sialic acid. The results provide valuable insights for the scientific community to understand which dairy ingredients represent good innate sources of NPN components in IF, such as nucleotides, peptides, choline and carnitine, which are routinely supplemented in IFs and are associated with various health benefits, including immune support, gut health, and growth and development. The knowledge generated in this study will also allow for informed decision-making for ingredient selection, which will enable the development of IFs with NPN profiles closer to human milk. Additional research opportunities in the NPN area have also been identified.