- High calcium intake (more than 2 servings of dairy products per day or taking calcium supplements > 3x/wk ) for 1 month prior to study start date and for duration of study. (If participant is taking calcium supplement > 3x/wk or more than 2 servings of dairy products per day, they are eligible to participate if they agree to stop for 1 month prior to study start date and for the duration of the study. Participants will similarly be asked to stop multivitamins as the majority of these supplements contain calcium.)