Threonine is an indispensable amino acid (nutrient containing nitrogen), which cannot be made in the body and must be consumed from food. Amino acids are the building blocks of protein in your body, and need to be eaten in required amounts to maintain health and growth. Deficiency in threonine can affect small intestine growth due to its structural importance in the intestinal protein mucin. While threonine is found in many foods, deficiency can occur in developing countries where nutrition is primarily plant based, and low in available protein.

Therefore, the purpose of this study is to determine the requirement of the indispensable amino acid Threonine, in school-aged children (6-10y). Secondly, we wish to determine the availability of threonine from three test proteins (soy, green pea, casein).

The threonine intake requirement for children are based on factorial calculations. In the current study we will use a new and modern technique, the indicator amino acid oxidation technique (IAAO), to determine threonine requirements in children.

This technique is a newer technique which involves the consumption of protein shakes composed of specific amounts of threonine mixed with a stable isotope tracer. The oxidation of this isotope will be measured in urine and breath to determine a breakpoint (requirement) of threonine.

Determining the requirement for threonine, as well as the availability of threonine from various food products will help us to develop better food recommendations for children.

Research Method This study will be carried out in a repeated measures design. Participants will be recruited and screened for eligibility. Six participants will be brought in for 6 testing visits with reference amino acid, where they will be randomized to a level of threonine intake. A further 3 visits will be carried out during which participants will be randomized to a level of threonine consumption derived from alternative proteins (casein, soy, peas) which is at a threshold below the requirement for threonine to determine availability.

Inclusion Criteria:

• Children between 6 and 10 Y
• No history of chronic disease or metabolic disorders
• No food allergies
• No recent illness or antibiotic consumption
• Children with a normal, healthy, body weight (between 3rd and 85th percentiles for their age group for weight) (Dietitians of Canada, 2015)

Exclusion Criteria:

• Children under 6 years' old

• Children over 10 years' old

• Children with a history of disease or metabolic disorders

• Children with any food allergies

• Children taking prescription medication

• Children with a history of being underweight, overweight, or obese (Dietitians of Canada, 2015; Onis et al., 2007)

  o Below 3rd percentile for weight, Above 85th percentile for weight

• Female children who have commenced menstruation