The Impact of Consumption of Eggs in the Context of Plant-Based Diets on Endothelial Function, Diet Quality, and Cardio-Metabolic Risk Factors in Adults at Risk for Type 2 Diabetes
Condition: Type 2 Diabetes; Cardiovascular Diseases
MeSH terms: Cardiovascular Diseases; Diabetes Mellitus, Type 2
Study type: Interventional

Summary: 
      Purpose To assess the impact of inclusion of 2 eggs daily for 6 weeks in an otherwise vegan
      diet compared to a vegan diet on cardio-metabolic risk and dietary pattern in adults at risk
      for type 2 diabetes.

      Hypotheses In comparison with a vegan diet, the inclusion of 2 eggs daily in an otherwise
      vegan diet will improve or have neutral effects on endothelial function and other markers of
      cardio-metabolic risk in adults at risk for type 2 diabetes.

      (2) In comparison with a vegan diet, the inclusion of 2 eggs daily in an otherwise vegan diet
      will improve diet quality and nutrient intake in adults at risk for type 2 diabetes.

      (2) In comparison with a vegan diet, the inclusion of 2 eggs daily in an otherwise vegan diet
      will improve diet quality and nutrient intake in adults at risk for type 2 diabetes.
    

Detailed description: 
      Specific Aims of the Proposed Project:

        1. To assess the impact of inclusion of 2 eggs daily for 6 weeks in an otherwise vegan
           diet, compared to a vegan diet, on endothelial function in adults at risk for T2DM.
           Specifically, to demonstrate superior or neutral effects on endothelial function with
           the inclusion of eggs in the context of otherwise vegan diets.

        2. To assess the impact of the inclusion of eggs daily for 6 weeks in an otherwise vegan
           diet, compared to a vegan diet, on dietary pattern and cardio-metabolic risk factors in
           adults at risk for T2DM. Specifically, to determine the effects on egg intake in the
           context of an otherwise vegan diet on diet quality and nutrient intake, lipid profile,
           blood pressure, insulin sensitivity and anthropometric measures.

      Design:

      Proposed is a randomized, single-blind, controlled, crossover trial designed with 2 treatment
      assignments (vegan diet plus eggs and vegan diet ) to compare the effects of 6 weeks of each
      treatment assignment on endothelial function, nutrient intake, diet quality, and
      cardio-metabolic risk factors in individuals at risk for T2DM. After a 4-week run-period of
      an ad libitum vegan diet, participants will be randomized to 1 of 2 possible sequence
      permutations and then undergo repeated measures following inclusion of 2 eggs per day in
      their otherwise vegan diet, or a vegan diet for 6 weeks, with a 4-week washout period between
      treatment assignments. The participants will continue their vegan diets during the 4-week
      washout period.

      Background In the United States (U.S.), diabetes is a public health problem of epidemic
      proportions, affecting more than 30 million individuals. Only 23.1 million of these
      individuals are diagnosed. An estimated 84.1 million adults aged 18 years and older have
      prediabetes. Nearly 1 out 10 individuals with prediabetes is aware that he or she has this
      condition. Fifteen to thirty percent of individuals with prediabetes are likely to develop
      Type 2 diabetes mellitus (T2DM) within 5 years. The total medical costs, including lost work
      and wages, for individuals diagnosed with diabetes are estimated to be $245 billion. When
      compared with individuals without diabetes, individuals with diabetes have a medical cost
      that is more than two times higher. When compared with those without diabetes, the risk of
      death in individuals with diabetes is more than 50% higher. Between 90% and 95% of all
      diagnosed cases of diabetes are T2DM. The complications of diabetes include stroke,
      hypertension, cardiovascular disease (CVD), blindness, kidney disease, nervous system damage,
      limb amputations, and biochemical imbalances that can cause acute life-threatening events.
      [1] When compared with those without diabetes, the rates of cardiovascular mortality are 2 to
      4 times higher among adults with diabetes.

      Obese individuals are more than seven times more likely to develop T2DM when compared with
      healthy weight individuals. The cells become more resistant to insulin when there is more
      body fat. Increased insulin resistance contributes to high blood pressure, increased low
      density lipoprotein (LDL) cholesterol and triglycerides, and reduced levels of high-density
      lipoprotein (HDL) cholesterol. High blood insulin levels are associated with increased body
      fat. They disrupt normal metabolism of fats, increasing blood cholesterol and triglyceride
      levels; interfere with intercellular communication, including blood pressure-regulating
      signals; and stimulate the sympathetic nervous system, increasing the cardiac contractility
      and arterial resistance. Weight gain of as little as 10 pounds over 15 years could double an
      individual's insulin resistance and increase the risk of diabetes. When fat is primarily
      stored in the abdomen, the risk of diabetes is increased compared with when the fat is stored
      elsewhere. Abdominal fat wrap around organs such as the liver that play a vital role in
      glycemic control. Accumulation of fat around the liver blocks the action of insulin, which is
      needed to lower blood sugar; as a result, glucose accumulates in the blood stream.

      Hyperglycemia has been linked to CVD. [Hyperglycemia stimulates a pro-atherogenic phenotype
      in the vessel wall of endothelial cells, vascular smooth muscle cells, inflammatory cells,
      fibroblasts, and platelets, leading to an atherosclerotic response. Diets with a low glycemic
      load have been shown to improve serum lipid profiles, reduce C-reactive protein (CRP) levels,
      and aid in weight management. [8] Low glycemic index diets have been associated with higher
      levels of HDL cholesterol, reduced CRP concentrations, and decreased risk of developing
      diabetes and CVD. [9] While glycemic control remains the basis of diabetes care, the
      co-management of cardio-metabolic risk factors and prevention of long-term consequences are
      also recognized as essential to improve long-term survival.

      Lifestyle intervention is the cornerstone for management and prevention of T2DM. Previous
      studies have shown that a reduction of as little as five to seven percent in body weight can
      lead to significantly improved cardio-metabolic risk factors among those at risk for T2DM.
      Patients with T2DM or at risk for T2DM are typically advised to consume foods with a low
      glycemic index (i.e., a relative ranking of carbohydrates in foods based on their impact on
      blood glucose levels). When steps are taken to ensure adequate consumption of nutrients,
      plant-based diets are recommended to reduce risk of T2DM. Without careful planning, it can be
      difficult for those consuming plant-based diets that exclude animal foods to consume optimal
      amounts of protein and other nutrients Vitamin B12 is present only in animal foods while
      iron, zinc, copper and selenium are more bioavailable when obtained from animal food sources.
      Eggs are rich in vitamins and minerals such as vitamin A, B2, B5, B12, phosphorus, selenium,
      iron and choline and contain the highest quality protein. Additionally, eggs are satiating
      and therefore have the potential to regulate calorie intake and reduce body weight. Hence,
      the inclusion of eggs in plant-based diets has the potential to improve diet quality by
      increasing intake of a variety of nutrients and ensuring the correct balance of nutritious
      foods. While some observational studies have identified associations between egg consumption
      and greater risk of T2DM, experimental trials in contrast have shown that eggs may improve
      insulin sensitivity and some cardio-metabolic risk factors in individuals with T2DM. In order
      to recommend eggs as part of a plant-based diet for this population, it is imperative to
      establish their effects on diet quality and cardio-metabolic health in the context of
      plant-based diets.
    

Intervention name(s): Egg included vegan phase; Vegan Phase
Intervention type(s): Other; Other
Intervention description(s): : Participants will meet with a registered dietitian and receive instructions to include 2 eggs per day for 6 weeks as part of their otherwise vegan diets. Participants will also receive instructions to preserve an isocaloric condition with the addition of 2 eggs in their diets. Counseling of the study participants will be based on the U.S. Department of Agriculture (USDA) healthy vegetarian meal plans, with modifications to exclude dairy products. [21] Additional resources (e.g., educational materials, recipes, etc.) for adopting and maintaining a vegan diet (with the exception of including eggs) will also be provided.; The participants will consume a vegan diet for 6 weeks. The study dietitian will provide counseling and sample meal plans based on the USDA healthy vegetarian dietary pattern, with modifications to exclude eggs and dairy products. Additional resources (e.g., educational materials, recipes, etc.) for adopting and maintaining a vegan diet will also be provided.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: To provide a sound basis for the statistical comparison of outcome measures for treatment assignments, participants will be randomized to 1 of 2 sequence permutations of an egg-included vegan diet and a vegan diet, which will begin after a 4-week run in phase. Each permutation will include a 6-week treatment phase, followed by a 4-week washout phase, followed by 6-week treatment phase (20 weeks total for each study participant, including the run-in phase).
Masking: Double (Investigator, Outcomes Assessor)
Primary purpose: Prevention