Twins Nutrition Study (TwiNS): Vegan vs. Omnivore (TwiNS)

This study is designed to investigate the health impact of a vegan diet compared to a usual, omnivorous diet. The investigators plan to study these diets in twins, where one twin follows a vegan diet and the other twin follows an omnivorous diet, thus the investigators control for genetic differences that might impact the effect of the diet.

Study Overview

• Status: Completed
• Conditions: Inflammation; Glucose Intolerance; Microbiome; Lipid Metabolism; Weight Change, Body; Immune Function
• Intervention / Treatment: Behavioral: Vegan diet; Behavioral: Omnivore diet

Detailed Description

During this study, the investigators will evaluate the nutrient intake in both the vegan and the omnivorous diet. The investigators will also measure physiologic markers of health such as lipid levels, HbA1C, heart rate, and weight, and they will also look at the effect of the diets on the microbiota. In addition to measuring the effect of the diet, the investigators will monitor adherence to the diet, and survey participants on the ease/difficulty in following a vegan diet as well as their energy levels and sense of wellbeing. Thus, this study will help us better understand the health impact and feasibility of following a vegan diet. These results will be of much interest to the general public and the health care professionals.

• Study Type: Interventional
• Enrollment (Actual): 44
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • California
    • Stanford, California, United States, 94305
      • Stanford University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Age 18+
• 1/2 of a pair of twins that will both be participating
• Willing to consume a plant-based diet (vegetables, fruit, whole grains, legumes, etc.)
• Willing to consume meat/eggs (beef, pork/sausage, chicken, eggs) >= 1 time a day
• Willing to consume dairy (milk, yogurt, cheese) >= 1 time a day

Exclusion Criteria:

• Weight < 110 lb
• BMI >= 40
• LDL-C > 190 mg/dL
• Systolic Blood Pressure > 160 mmHg OR Diastolic blood pressure > 90 mmHg
• Pregnant, lactating or planning to become pregnant during the course of the study.

• Use of any of the following drugs/supplements within the last 2 months:

  • systemic antibiotics, antifungals, antivirals or antiparasitics (intravenous, intramuscular, or oral);
  • corticosteroids (intravenous, intramuscular, oral, nasal or inhaled);
  • cytokines;
  • methotrexate or immunosuppressive cytotoxic agents.
• Chronic, clinically significant, or unstable (unresolved, requiring on-going changes to medical management or medication) pulmonary, cardiovascular, gastrointestinal, hepatic or renal functional abnormality, as determined by medical history, Type 1 diabetes, dialysis
• History of active cancer in the past 3 years except for squamous or basal cell carcinomas of the skin that have been medically managed by local excision
• Unstable dietary history as defined by major changes in diet during the previous month, where the subject has eliminated or significantly increased a major food group in the diet.
• Recent history of chronic excessive alcohol consumption defined as more than five 1.5-ounce servings of 80 proof distilled spirits, five 12-ounce servings of beer or five 5-ounce servings of wine per day; or > 14 drinks/week.
• Any confirmed or suspected condition/state of immunosuppression or immunodeficiency (primary or acquired) including HIV infection, multiple sclerosis and Graves' disease.
• Surgery of the GI tract, with the exception of cholecystectomy and appendectomy, in the past five years. Any major bowel resection at any time.
• Regular/frequent use of smoking or chewing tobacco, e-cigarettes, cigars or other nicotine-containing products
• Regular use of prescription opiate pain medication

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Vegan; Participants will be asked to consume a healthy vegan diet.	Behavioral: Vegan diet; Healthy vegan diet.
Experimental: Omnivore; Participants will be asked to consume a healthy omnivore diet.	Behavioral: Omnivore diet; Healthy omnivore diet.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in LDL cholesterol	Difference in the 8-week change-from-baseline in LDL cholesterol between the vegan vs. omnivore diet groups	Baseline and 8 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in triglycerides	Difference in the 8-week change-from-baseline in triglycerides between the vegan vs. omnivore diet groups	Baseline and 8 weeks
Change in inflammatory markers	Difference in the 8-week change-from-baseline in inflammatory markers detected in blood samples between the vegan vs. omnivore diet groups.	Baseline and 8 weeks
Change in alpha diversity	Change from baseline in alpha diversity at 8 weeks in the vegan and omnivore diet groups. We will be using the number of observed sequence variants ("species") determined by standard 16S rRNA amplicon sequencing (V3-V5 region followed by DADA2 to define error-corrected sequence variants) as our primary metric of alpha diversity. We will also determine whether there is a change in observed sequence variants between the two groups. Higher alpha diversity is better. The units are the number of sequence variants.	Baseline and 8 weeks

Collaborators and Investigators

• Sponsor: Stanford University
• Investigators: Principal Investigator: Christopher D Garnder, PhD, Stanford University

Publications and helpful links

General Publications

• Landry MJ, Ward CP, Cunanan KM, Durand LR, Perelman D, Robinson JL, Hennings T, Koh L, Dant C, Zeitlin A, Ebel ER, Sonnenburg ED, Sonnenburg JL, Gardner CD. Cardiometabolic Effects of Omnivorous vs Vegan Diets in Identical Twins: A Randomized Clinical Trial. JAMA Netw Open. 2023 Nov 1;6(11):e2344457. doi: 10.1001/jamanetworkopen.2023.44457. Erratum In: JAMA Netw Open. 2023 Dec 1;6(12):e2350422.

Helpful Links

• Study description

Study record dates

Study Major Dates

• Study Start (Actual): March 17, 2022
• Primary Completion (Actual): July 20, 2022
• Study Completion (Actual): July 20, 2022

Study Registration Dates

• First Submitted: March 17, 2022
• First Submitted That Met QC Criteria: March 17, 2022
• First Posted (Actual): March 28, 2022

Study Record Updates

• Last Update Posted (Actual): January 12, 2024
• Last Update Submitted That Met QC Criteria: January 10, 2024
• Last Verified: December 1, 2023

More Information

Terms related to this study

• Keywords: Inflammation; Microbiome; Lipids; Glucose; Body weight; Immune function
• Additional Relevant MeSH Terms: Pathologic Processes; Glucose Metabolism Disorders; Metabolic Diseases; Body Weight; Hyperglycemia; Inflammation; Glucose Intolerance; Body Weight Changes
• Other Study ID Numbers: 63995

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No