Assessment of the Protein Quality of Cereal Grains in School-aged Children

Purpose The purpose of this research project is to implement the minimally invasive Indicator Amino Acid Oxidation (IAAO) method in healthy school-aged children to measure the metabolic availability of the essential amino acid lysine obtained from commonly consumed cereal grains and their breakfast counterparts. Additionally, the difference in metabolic availability through complementation of breakfast cereals with milk will be assessed.

Hypothesis The use of the IAAO method will yield a higher lysine metabolic availability for those cereal grains that have the least amount of fibre in the food matrix. Combining the consumption of cereals with milk will increase the metabolic availability of lysine.

Justification Cereal grains and their derived products are the most commonly consumed food group around the world. From traditional foods such as steamed rice, corn tortillas, and wheat bread to relatively modern products like ready-to-eat breakfast cereals. Up to 80% of the energy intake in developing countries comes from this food group. Given that they are considered as a low protein quality food source, a considerable amount of the world's population could potentially be at risk of lysine deficiency. Especially, children living in underdeveloped countries where complementation with other food sources, such as legumes, dairy, or other animal products, is not an available option. Since lysine is the limiting amino acid in cereals, this study is of great importance not only for its nutritional value, but also for its social and economic impact.

Current lysine recommendations for school-aged children are based on factorial calculations performed on results of adult male studies. To develop the Lysine EAR (Estimated Average Requirement) for growing children, these studies use adult lysine maintenance requirements multiplied by estimated rates of protein deposition and the efficiency of this deposition. Additionally, these studies do not measure lysine's bioavailability, which will vary depending on the food sources and the processing techniques used to preserve them. With these limitations in mind, the IAAO method has the capacity to accurately measure amino acid metabolic availability in different populations groups, such as healthy and malnourished children. Metabolic availability refers to the amount of absorbed amino acids that are used for protein synthesis. It takes into account all amino acid losses from digestion, absorption, metabolic utilization, and endogenous losses.

Previously, this method was used to determine lysine metabolic availability of rice in healthy adults. This is the only study of this nature done for any human food source. Currently, there is no information available regarding lysine's metabolic availability from corn, wheat, milk and any breakfast cereal. Previously the IAAO method has successfully been implemented in healthy Canadian and Indian children to measure lysine requirements. Additionally, lysine requirement studies has been preformed in moderately undernourished Indian children with parasitic intestinal infections. The study conclusions were that, undernourished children require around 20% more lysine than their healthy counterparts. In these cases it is not only important to know the lysine content of a food source, but also it's metabolic availability, to develop accurate interventions that will have a better chance to meet children's daily requirements.