Effect of Vegetarian/Vegan Diets on Cardiometabolic Risk: Systematic Reviews and Meta-analyses of Randomized Controlled Dietary Trials to Provide Evidence-based Guidance for Nutrition Guidelines Development
Trial Snapshot
- Phase
- Not Applicable
- Sponsor
- University of Toronto
- Enrollment
- 1
- Primary Endpoint
- HbA1c
Study Overview
Brief Summary
Vegetarian and vegan diets have been shown to reduce chronic disease risk, including diabetes and cardiovascular disease, as well as several cardiometabolic risk factors. Whether vegetarian and/or vegan dietary patterns improve cardiometabolic risk factors in individuals with diabetes remains unclear. To address the uncertainties, the investigators propose to conduct a series of systematic reviews and meta-analyses of the totality of the evidence from randomized controlled trials to distinguish the effect of vegetarian and/or vegan diets on the prevention and management of diabetes. The findings generated by this proposed knowledge synthesis will help improve the health of consumers through informing evidence-based guidelines and improving health outcomes by educating healthcare providers and patients, stimulating industry innovation, and guiding future research design
Detailed Description
Background: Vegetarian and/or vegan dietary patterns have been shown in prospective cohort and cross-sectional studies to be associated with lower diabetes risk and all-cause mortality. Evidence from systematic reviews and meta-analyses of controlled trials also suggest that vegetarian diets may be beneficial for glycemic control, blood lipids, weight loss, and blood pressure. On the contrary, evidence from previous meta-analyses of prospective cohort studies, as well as more recent prospective cohort studies have shown that diets higher in animal protein, specifically in red meat, are associated with an increased incidence of T2D. The effect of following a vegetarian/vegan dietary pattern on cardiometabolic risk factors in individuals with diabetes is less clear. Furthermore, not all diabetes guidelines recommend following a vegetarian and/or vegan dietary pattern for the management of diabetes or they provide a low-grade evidence rating.
Need for proposed research: High quality systematic reviews and meta-analyses of randomized controlled trials represent the highest level of evidence to support dietary guidelines and public health policy development. As dietary guidelines and public health policy have shifted toward food and dietary-pattern based recommendations, there is a need for systematic reviews and meta-analyses comparing the role of vegetarian/vegan diets in the prevention and management of diabetes.
Objective: To improve evidence-based guidance for diabetes guidelines and public health policy development, the investigators will conduct a series of systematic reviews and meta-analyses of the effects of vegetarian/vegan diets on cardiometabolic risk factors in individuals with diabetes including measures of (1) glycemic control, (2) blood lipids, (3) adiposity and (4) blood pressure.
Design: Each systematic review and meta-analysis will be conducted according to the Cochrane Handbook for Systematic Reviews of Interventions and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).
Data sources: MEDLINE, EMBASE, and The Cochrane Central Register of Controlled Trials (Clinical Trials; CENTRAL) will be searched using appropriate search terms supplemented by manual searches of references of included studies.
Study Design
- Study Type
- Observational
- Time Perspective
- Prospective
Eligibility Criteria
- Sex
- All
- Accepts Healthy Volunteers
- No
Inclusion Criteria
- •Dietary trials in humans
- •Randomized treatment allocation
- •Suitable control (i.e. isocaloric diet that is not vegetarian or vegan)
- •Viable endpoint data
Exclusion Criteria
- •Non-human studies
- •Non-randomized treatment allocation
- •<3 weeks
- •Lack of a suitable control (i.e. non-isocaloric)
- •No viable endpoint data
Outcomes
Primary Outcomes
HbA1c
Time Frame: Up to 1.5-years
Secondary Outcomes
- Fasting glucose(Up to 1.5-years)
- Triglycerides(Up to 1.5-years)
- Body weight(Up to 1.5-years)
- Body mass index (BMI)(Up to 1.5-years)
- Systolic blood pressure(Up to 1.5-years)
- non-HDL-cholesterol(Up to 1.5-years)
- Fasting insulin(Up to 1.5-years)
- LDL-cholesterol(Up to 1.5-years)
- HDL-cholesterol(Up to 1.5-years)
- Waist circumference(Up to 1.5-years)
- Diastolic blood pressure(Up to 1.5-years)
Investigators
John Sievenpiper
MD, PhD, FRCPC
University of Toronto