Protein requirements of malnourished children under a high pathogen burden

Chronic undernutrition is an intractable problem, as illustrated by the global prevalence in children under the age of 5 years.  Although the worldwide incidence of undernutrition is declining, childhood stunting is falling short of the target of a 40% reduction by 2025. Even then, this would comprise some 100 million cases worldwide. Dietary protein, which delivers indispensable amino acids, contributes over half of the body’s daily requirements of essential nutrients. However, in undernourished children, supplements aimed to provide sufficient protein according to FAO recommendations, often fail to promote growth.

A daily supply of protein is required to maintain gut integrity and to support the production of immune defences. Protein deficiency can lead to decreased gut barrier function and reduced immune function. There is evidence that protein requirements may be higher in the presence of a pathogen burden. However, the evidence is of reduced amino acid absorption and does not identify if the capacity to digest dietary protein is reduced.  Protein digestion is a complex multi-stage process and evidence for digestive dysfunction is lacking. Reduced efficiency at any stage may result in fewer indispensable nutrients being absorbed and failure to thrive. Nutrients that are not absorbed can become available to the gut microbiome and potentially, gut pathogens. Studies in malnourished subjects have shown reduced markers of protein digestion (low digestive enzymes in stool). A few studies using invasive techniques have reported reduced pancreatic enzyme secretions. Thus far, more accurate minimally invasive functional tests of protein digestion are lacking. We aim to address this knowledge gap.