Canada's Food Guide places an increased emphasis on plant-based proteins; however, Canadians who consume a plant-based diet may be compromised because of intake of lower-quality protein. Consumption of high-quality protein is important during growth and development, especially in highly active individuals. The study will compare milk (i.e. high quality protein) to a pea-based beverage (i.e. lower quality plant-based protein) in adolescent boys and girls who are engaged in resistance-training programs as part of their athletic training. One-hundred and fourteen adolescent boys and girls (12-17y of age) will be divided into groups that consume milk, a pea-beverage, or a carbohydrate (sugar) beverage after resistance training sessions performed three times per week for six months. It is predicted that the group consuming milk will have greater increases in muscle mass, strength, and bone density, and greater reductions in fat mass compared to the groups consuming a pea-based or carbohydrate beverages.

Milk protein is important especially for very active people and in the context of plant-based diets, which are lower in protein quality. The purpose of the study is to compare the effectiveness of milk supplementation to pea-beverage supplementation during resistance training programs for increasing lean tissue mass in adolescent boys and girls. Secondary and tertiary outcomes include fat mass, bone mineral density, and muscular strength. It is hypothesized that milk supplementation during resistance training will be more effective than plant-based proteins (i.e. pea-beverage) for increasing muscle mass, reducing fat mass, and improving bone mineral outcomes in adolescent boys and girls. One-hundred and fourteen boys and girls (aged 12-17y) who are currently enrolled in resistance training programs (3 times per week for 6 months) as part of their competitive athletic programs will be stratified by sex and maturity status before being randomized to three groups: 1) 1% chocolate milk supplementation; 2) pea-based beverage; 3) carbohydrate beverage (placebo control). Beverages will be consumed during recovery from each resistance training session (i.e. 250 ml immediately after training and 250 ml one hour later to optimize post-exercise protein synthesis) over the six-month intervention. It is anticipated that milk supplementation will be more effective than plant-based protein supplementation.

Inclusion Criteria:

• Currently participating in a resistance-training program 3 times per week
• Female participants must have reached menarche

Exclusion Criteria:

• Have taken any nutritional supplement (e.g., protein, creatine, amino acids) within the past month
• Currently taking anabolic steroids or oral corticosteroids
• Allergies to dairy, almonds, cashews, or peas