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UBC Theses and Dissertations

Determination of the lysine bioavailability from cereal food sources in healthy school-aged children Caballero de la Peña, Katia


Background: Cereal grains provide essential nutrients and dietary energy (38-80% daily) as part of staple diets globally. Proteins in cereals contain relatively low amounts of lysine, an essential amino acid, which can potentially limit growth in children. Losses within digestion, absorption and utilization combined with losses from cooking may further decrease bioavailable lysine. Objectives: To assess lysine bioavailability from commonly consumed foods (white rice, oats, corn, black beans, and whole milk) in healthy school-aged children; and to determine the effects of food matrix and cooking techniques on lysine bioavailability. Methods: Using a repeated-measured design and a stable isotope-based technique (Indicator Amino Acid Oxidation, IAAO), three experiments were conducted where 5-6 children aged 6-10y participated per experiment (totaling 143 study days) to evaluate lysine bioavailability from test foods. The effects of food matrix and cooking techniques were analyzed using in-vitro assays - Differential Scanning Calorimeter (DSC) for starch retrogradation and colorimeter for Maillard Reaction Products (MRPs) formation. Results: Lysine bioavailability from rice was high (97%), but consuming rice cold reduced it to 86.1%. DSC analysis showed that cold rice samples had retrograded starch within their food matrix. Lysine bioavailability was high in milk (103.7%) compared to black beans (81.5%). When oats were consumed as oatmeal (moist-heat cooking), lysine bioavailability was 92.7%; when the same oats were prepared as granola (dry-heat cooking), lysine bioavailability was reduced to 43.2%. A similar pattern was observed for corn atole (moist-heat cooking) had a higher lysine bioavailability (96.8%) than corn tortillas (dry-heat cooking) (75.4%). Color change analysis showed a higher magnitude of browning for granola (68%) compared to oatmeal, and for tortilla (17%) compared to atole, suggesting possible formation of reaction compounds and brown pigments derived from Maillard reaction leading to reduced bioavailability. Conclusion: Lysine was highly bioavailable within warm and moist-heat cooked foods, whereas reduced bioavailability was observed when foods were consumed cold and cooked using dry-heat. With the lysine bioavailability data obtained from this dissertation, improved dietary recommendations that meet lysine requirements from foods can be developed for children who consume a predominantly cereal/plant-based diet.

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