Study #3070: Dairy Fat & Fermentation Study

For more information about enrolling in this study, please call:

Purpose of this study: The purpose of this study is to compare the effect of consuming full-fat (regular) and fat-free (skim) milk, as well as full-fat and fat-free yogurt (a fermented dairy product) on risk factors for heart disease. We will also determine whether consuming these dairy products changes the types of microorganisms in your mouth and gut, as well as the products produced by the gut microbes. The results may facilitate refinement of public health dietary guidance for dairy product consumption.

Target population:
Men and postmenopausal women, ages 50 years and older.

Inclusion criteria:

  • Age ≥50 years
  • Men and postmenopausal women
  • BMI ≥25 and ≤35 kg/m2
  • No milk allergy, lactose intolerance or adherence to vegan or other dietary pattern that excludes dairy products
  • Willing to consume 2 servings/ day of the dairy food items provided
  • Usual pattern of bowel movements at least every other day

Major exclusions:

  • Diagnosis of diabetes, chronic heart, kidney, liver and gastrointestinal disorders
  • Taking medications or dietary supplements that will affect the study outcomes
  • Unwilling to forgo additional milk and yogurt consumption during each 3-week diet phase

Length of study:

  • 18 weeks


  • None

Time commitment/number of visits:

  • 12 total visits to the center and up to 10 telephone administered questionnaires:
    • Visit 1 (week 1): up to 90 mins
    • Visit 2, 5, 8 and 11 (Weeks 2, 7, 12 and 17); approximately 10-15 mins/visit
    • Visit 3, 6, 9 and 12 (Weeks 3, 8, 13 and 18; approximately 30-45 mins/visit
    • Visit 4, 7 and 10 (Weeks 6, 11 and 16; approximately 30 mins per visit)

NOTE: These visits will involve collection of blood, stool and mouth swab samples, measurement of height, weight, waist circumference, and blood pressure, filling out questionnaires either in person or over the telephone,answering oral hygiene questions, and picking up your dairy food items. You will also have to come into the center at least an additional 4 times to drop off stool samples.

Can I work?

  • Yes, but if subjects employed by Tufts University qualify to participate in the study, they cannot participate as subjects during hours in which they are being compensated by Tufts.


  • Up to $625 for participants who qualify and complete the entire study.