Dairy Fat and Fermentation Study

NCT ID: NCT05840081

Last Updated: 2025-12-12

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 37 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2023-10-01
• Study Completion Date: 2025-08-19

Brief Summary

The purpose of the 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 microorganisms in your gut as well as the products produced by the gut microbes. We will also determine whether consuming these dairy products affects risk factors for heart disease.The findings of the study will help us determine if heart disease risk factors are modified by the fat content and fermentation of milk. The results may facilitate refinement of public health dietary guidance for cardiovascular disease risk reduction.

Detailed Description

A randomized-controlled cross-over trial will be conducted to compare the effect of two servings per day of full-fat and fat-free milk, and full-fat and fat-free yogurt (hence forth referred to as dairy food items) on the gut microbiome, fecal and serum metabolome, and determine their relation to cardiometabolic risk factors (CMRF) and functional pathways associated with the differences identified. Participants will be provided with 2 servings per day of the test dairy products and requested not to consume additional bovine (cow) milk or yogurt during each 3-week diet phase.They will be allowed to use dairy substitutes such as plant-based milk alternatives and consume other types of dairy products (e.g. cheese).

The study consists of four diet phases: fat-free milk phase, full-fat milk phase, fat-free yogurt phase and full-fat yogurt phase. Each diet phase is 3 weeks in duration, separated by a 2 week break. Participants will be provided with 2 servings of a dairy based food item per day specific to their assigned phase and asked to consume them at two separate times during the day - morning and evening. Weight, waist circumference and blood pressure will be measured, blood and stool samples will be collected, and participants will complete two 24-hr food recall questionnaires during each phase.

Conditions

Heart Diseases; Microbial Colonization; Inflammation

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: TREATMENT
• Blinding Strategy: QUADRUPLE

Study Groups

Full-fat milk beverage

Beverage made with full-fat milk

Group Type: EXPERIMENTAL

Milk or yogurt beverage

Intervention Type: OTHER

Commercially available milk or yogurt (depending on experimental arm) will be incorporated into flavored drinks/smoothies to minimize perceived differences among these items, preserving the double-blind nature of the study design.

Fat-free milk beverage

Beverage made with fat-free milk

Group Type: EXPERIMENTAL

Milk or yogurt beverage

Intervention Type: OTHER

Commercially available milk or yogurt (depending on experimental arm) will be incorporated into flavored drinks/smoothies to minimize perceived differences among these items, preserving the double-blind nature of the study design.

Full-fat yogurt beverage

Beverage made with full-fat yogurt

Group Type: EXPERIMENTAL

Milk or yogurt beverage

Intervention Type: OTHER

Commercially available milk or yogurt (depending on experimental arm) will be incorporated into flavored drinks/smoothies to minimize perceived differences among these items, preserving the double-blind nature of the study design.

Fat-free yogurt beverage

Beverage made with fat-free yogurt

Group Type: EXPERIMENTAL

Milk or yogurt beverage

Intervention Type: OTHER

Commercially available milk or yogurt (depending on experimental arm) will be incorporated into flavored drinks/smoothies to minimize perceived differences among these items, preserving the double-blind nature of the study design.

Interventions

Milk or yogurt beverage

Commercially available milk or yogurt (depending on experimental arm) will be incorporated into flavored drinks/smoothies to minimize perceived differences among these items, preserving the double-blind nature of the study design.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

1. Age >50 years

2. Men and postmenopausal women

3. BMI >25 and <35 kg/m2

4. No milk allergy, lactose intolerance or adherence to vegan or other dietary pattern that excludes dairy products

5. Non-smoker

6. Usual pattern of bowel movements at least every other day.

Exclusion Criteria

1. Women and men <50 years

2. Women, pre- or peri-menopausal

3. BMI <25 and >35 kg/m2

4. Current smokers or former smoker who quit < 6 months

5. Use of nicotine replacement products within last 6 months

6. Replacement or gender affirming hormonal therapy use

7. Weight gain of >15 pounds within last 6 months

8. Infrequent bowel movements

9. History of anemia within past 2 years or confirmation of anemia at first study visit

10. Blood donation within last 2 months

11. Untreated hypertension

12. Oral antibiotics use within 2 weeks of study entry

13. Steroid use (including dental prophylaxis use within 2 wks prior to or during study, except non-prescription topical and nasal steroids, e. g. Flonase)

14. Use of lipid lowering medications

15. Chronic use of aspirin, non-steroidal anti-inflammatory medications (NSAIDS), laxatives, anti-diarrheal medication

16. Regular use (>2 times per week) of acid lowering medication: antacids, proton pump inhibitors, or H2 Blockers.

17. Use of dietary supplements other than multi-vitamins, including pre- and probiotics, within 2 months of study entry

18. Milk allergy, lactose intolerance or adherence to vegan or other dietary patterns that exclude dairy products

19. Colonoscopy within 3 weeks of study entry or during study period

20. Diagnosis of malabsorption, inflammatory bowel disease (ulcerative colitis or Crohn's Disease), cirrhosis, history of gastrointestinal resection (other than appendectomy), chronic pancreatitis or any other chronic GI disease that in the opinion of the study physician would alter the study results

21. Chronic heart, liver, thyroid, renal or kidney disease

22. Type I or type II diabetes

23. Alcohol consumption >7 drinks/week for women and >14 drinks/week for men

24. Inadequate refrigerator storage capacity to store 21 8-oz containers of milk or yogurt

25. Participation in other dietary intervention research study during the same time

26. No social security number

27. Not willing to commit to adhering to the protocol

• Minimum Eligible Age: 50 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Tufts University

OTHER

Sponsor Role: lead

Responsible Party

Alice Lichtenstein

D.Sc.

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Alice H Lichtenstein, D. Sc.

Role: PRINCIPAL_INVESTIGATOR

Tufts University

Locations

Jean Mayer Human Nutrition Research Center on Aging

Boston, Massachusetts, United States

Countries

United States

Other Identifiers

3070

Identifier Type: -

Identifier Source: org_study_id