Comparison of Dairy and Plant-based Alternatives in Adolescents and Older Adults

To join this study, you need to be a healthy person aged between 14-18 years old (teenagers) or 60-75 years old (older adults). For teenagers, your weight should be within certain healthy ranges. For older adults, your Body Mass Index (BMI), which is a measure of weight relative to height, should be between 25 and 30.

There are also some important things that would mean you can't take part. For example, if you smoke, have thyroid problems, or are allergic to dairy or other foods used in the study, you wouldn't be able to join. You also can't have certain health conditions like diabetes, heart disease, or kidney disease. If you regularly skip breakfast, are on a special diet like 'keto', or have difficulty eating, you also wouldn't be suitable. The study also can't accept people who have high blood pressure that isn't under control, or if your blood sugar is too high when we first check it.

It's important that you're willing to keep your usual diet, exercise, and weight steady throughout the study. You'll also need to agree not to drink alcohol or do intense exercise for 24 hours before each study visit, and avoid cannabis or protein powder supplements during the whole study. You'll need to understand the study steps and agree to take part.

If you decide to take part, you'll visit the Nutrition Intervention Center at the University of Toronto three times. The first visit is a screening appointment, which takes about 30 minutes, to make sure you're suitable for the study. After that, there will be two study visits, each lasting about 2 hours and 30 minutes. The whole study will take at least two weeks to complete.

Before each of your two main study visits, you'll need to fast (not eat anything) for 12 hours overnight. On the days before these visits, you'll also be asked to stick to your normal diet and sleep patterns, and avoid any strong exercise or alcohol. During the main visits, you'll be given either a dairy product or a plant-based alternative, along with a pizza meal. Throughout these visits, you'll fill out questionnaires about how you're feeling and provide small blood samples. These samples will be taken both through a quick finger prick and from a vein in your forearm, to check your blood sugar, insulin, hormones, and other nutrients. You will be compensated for your time and any travel expenses you have.