Assessment of Dietary Protein and Amino Acid Requirements in Children below 5 Years of Age

In 2050 there will be approximately 10 million people to feed globally. This population surge coupled with forces like climate change will limit access to nutritious foods with the right balance of both macronutrients and micronutrients. In particular, the supply of adequate dietary protein with optimum quality to meet essential amino acid requirements across age and physiological groups will be a major challenge. Dietary protein intake in high income countries is high and is largely based on animal source foods, a situation that is linked to adverse environmental footprint associated with intensive livestock production. In this context, the world is looking for ways to provide dietary protein that balances both human and environmental health; as such there is a recommendation to reduce intake of animal protein sources and shift to more plant-based diets. This recommendation is not context sensitive as currently dietary protein intake in low and middle-income countries is far below the global average and is predominantly plant based.  It is well documented that plant-based dietary protein is of low quality compared to animal source proteins that are easily absorbed and utilised by the human body. Alternative dietary proteins have been proposed as a solution as they are thought to be environmentally friendly, sustainable and in most cases, they have comparatively higher concentration of protein and other nutrients such as iron, zinc and essential fatty acids. Alternative proteins can be derived from plants (legumes and pulses, cereals, pseudo-cereals, oilseeds), algae, fungi, and insects (beetles, crickets, termites, mealworm, silkworm, etc). However, the nutritional value of alternative dietary protein sources is yet to be fully understood. The digestibility of protein from these alternative foods remains to be documented. A joint FAO-IAEA Technical Meeting held in 2022 recommended generation of data on true ileal digestibility of underutilised foods, including alternative proteins to facilitate the building of a comprehensive database on dietary protein digestibility that would eventually facilitate discussions on protein requirements across age and physiological groups. The Coordinated Research Project (CRP) aims to generate new information amino acid digestibility from alternative protein sources. Secondary objectives will include 1) to test the acceptability of diet formulations containing alternative dietary sources; 2) to assess the amino acid profile for alternative dietary protein sources and 3) to assess the effect of factors related to amino acid bioavailability such as processing, anti-nutritive factors and food matrix. Two stable isotope techniques will be used to generate data under this CRP: 1) the dual tracer isotope technique (DSIT) will be used to assess protein and amino acid digestibility. DSIT involves a first step where the target food is intrinsically labelled with a stable isotope tracer such as deuterium, 15N, 13C during production/growth after which the uniformly labelled food is incorporated into a test meal to which a second stable isotope labelled highly digestible protein or crystalline amino acid is added before consumption by a study participant. Digestibility is calculated as the ration between the isotope enrichment in amino acids in blood or breath relative to the original enrichment in the test meal. Digestibility value is used to calculate DIAAS based on reference patterns for each individual amino acids depending on the age and gender of the participant; 2) the indicator amino acid oxidation (IAAO) will used to measure amino acid metabolic availability. IAAO is premised on the assumption that if one essential amino acid is deficient in a food, all the other amino acids will be oxidized until the requirement for the limiting a amino acid is met at which point there is no further oxidation, making the rise in protein synthesis. For example, in cereals, the MA of lysine can be tested by varying the intake of lysine following a specific protocol (typically 8 hours for an adult); the oxidation of phenylalanine, the indicator amino acid, is measured over that period. Additionally, data on protein and amino acid digestibility will be generated based on pig model and compared to data from DSIT. Pig model closely mimics human digestion and is ranked 2nd in preference on methods to assess protein digestibility. Results from this CRP are expected to inform the design dietary guidelines for optimum protein intake in diverse population groups in the context of changing food systems that demand sustainable consumption that balance both human and planetary health.