Nutrition Science

Nutrition research is the underpinning of our programs and outreach. ENC is dedicated to providing accurate and up-to-date information on eggs, nutrition and health. Below is a collection of both ENC-funded research and relevant studies.

To learn more about our competitive research program, click here.

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Nutrition research: a messy science

Featured article in the Winter 2015 Issue of Nutrition Close-Up; written by Tia M. Rains, PhD

Imagine that you’ve just identified a substance with preliminary evidence that suggests it is effective in preventing a particular disease. In this case, let’s pretend that the condition is type 2 diabetes (T2D) and that the substance is an extract. To test whether the extract prevents the onset of T2D, you would conduct a randomized, controlled intervention trial (RCT). Those individuals at risk for the development of T2D (e.g., those with prediabetes) would be recruited and upon meeting the prespecified entry criteria, they would be randomized to receive a capsule that contained either the extract or an identical-looking capsule that acted as a placebo.

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Can culinary medicine succeed where diet drugs don’t?

Featured article in the Winter 2015 Issue of Nutrition Close-Up; written by John La Puma, MD

Recent approvals of obesity drugs Qsymia (Vivus) and Belviq (Arena) may help clinicians seeking solutions for their overweight patients. But many physicians still remember Phen-Fen with a shudder: heart valve abnormalities in young women put a stop to that off label combo in 1997. Other available diet drugs1 have not performed well enough to help doctors overcome their fear of liability, or help enough patients overcome their fear of failure.

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Read Papers from The Controversial Role of Macronutrient Composition in Diabetes and Related Disorders

In 2013, ENC sponsored and organized a satellite symposium “The Controversial Role of Dietary Protein in Diabetes and Related Disorders” chaired by Mitch Kanter, PhD, Executive Director, ENC, held in conjunction with the American Society for Nutrition’s 2013 Advances and Controversies in Clinical Nutrition Conference (December 5-7,2013) in Washington, DC.

The program featured presentations which provided an overview of the available evidence on macronutrient composition and specifically, dietary protein, in the prevention and management of diabetes and diabetes-related risk factors. Coordinated by Tia Rains, PhD, Senior Director, Nutrition Research & Communications, ENC, proceedings were recently published in a supplement within Journal of Nutrition titled: The Controversial Role of Macronutrient Composition in Diabetes andRelated Disorders of the Journal of Nutrition.

Click below to access the online reprint of each article:

Kevin C Maki and Alyssa K Phillips. Dietary Substitutions for Refined Carbohydrate That Show Promise for Reducing Risk of Type 2 Diabetes in Men and Women

Amy P Campbell and Tia M Rains. Dietary Protein Is Important in the Practical Management of Prediabetes and Type 2 Diabetes

Theresa A Nicklas, Carol E O’Neil, and Victor L Fulgoni III. Differing Statistical Approaches Affect the Relation between Egg Consumption, Adiposity, and Cardiovascular Risk Factors in Adults

Barbara A Gower and Amy M Goss. A Lower-Carbohydrate,Higher-Fat Diet Reduces Abdominal and Intermuscular Fat and Increases Insulin Sensitivity in Adults at Risk of Type 2 Diabetes

Can People with Heart Disease Start Eating Eggs Again?

Eggs-One-CrackedFor the past several decades, individuals with heart disease or at high risk for the development of heart disease have been advised to consume <200 mg/day of dietary cholesterol, whereas healthy adults are advised to consume <300 mg/day. Such recommendations are based on the assumption that dietary cholesterol produces harmful increases in blood cholesterol, which increases risk for developing atherosclerosis.

However, this simplistic thinking of A (i.e., dietary cholesterol) increases B (i.e., blood cholesterol) which increases C (i.e., heart disease risk) has been challenged in recent years as advances in diet and cardiovascular disease (CVD) research have revealed that the story is not that straight forward .  We now know that there are other risk factors that influence heart disease risk potentially as much as or more so than elevated blood cholesterol (e.g., inflammation, vascular function, etc.). And with regards to blood cholesterol, not all types of “bad” cholesterol (LDL-cholesterol) may be atherogenic.  Finally, dietary patterns may be more important for influencing CVD risk markers than isolated components, like dietary cholesterol.  And dietary cholesterol may not adversely affect CVD risk factors to the same degree as was previously thought.

Consistent with this thinking is a recently published paper by Dr. David Katz from the Yale University School of Medicine.  His laboratory evaluated 32 patients with documented coronary artery disease who consumed one of three daily breakfast treatments for 6 weeks each: 2 eggs/day; ½ cup of Egg Beaters/day; high-carbohydrate meals such as a bagel, waffles, pancakes, and cereal with milk.  Each treatment period was separated by a 4-week washout.

A number of different cardiovascular risk markers were measured before and after each 6-week intervention period.  Compared to the high-carbohydrate condition, 2 eggs/d did not adversely affect flow-mediated dilatation (an indicator of vascular function), blood cholesterol, blood pressure, or body weight. Further, there were no differences between the 2 egg/day and Egg Beaters conditions.  This despite the fact that cholesterol intake was 742 mg/d in the egg group versus ~200 mg/d in the Egg Beaters and high-carbohydrate breakfast conditions.

This is the first clinical intervention study to evaluate the effects of cholesterol/egg intake on multiple cardiovascular risk markers, including endothelial function, in patients with diagnosed CVD.  The investigators state in the paper that, “Excluding eggs from the diets of patients with CVD as per the AHA dietary recommendations could potentially lead to alternate choices high in starch and sugar, potentially associated with increased CVD morbidity and mortality.”

Although this study was small and relatively short in duration, the results certainly challenge the current thinking around cholesterol restrictions for those with CVD.  As is always the case in nutrition science, additional research is needed to better understand the role of dietary cholesterol in disease risk and progression.

Physiological Impacts of Protein and Effects on Weight Management

ENC likes to provide the opportunity for up and coming investigators to showcase their research, and today’s post comes from a student of Jamie I. Baum, PhD, Assistant Professor of Nutrition at the University of Arkansas. Dallas Johnson is a graduate of the University of Arkansas receiving a B. S. in Biology. He now works as a research associate in Dr. Jamie Baum’s lab conducting projects focusing role of dietary protein on energy metabolism and metabolic health. Dallas has recently been accepted in to medical school and will be starting in the fall of 2015.

lab-scientist-stock-photoMore than one third of Americans are obese, making obesity a very real public health concern (1). Obesity comes with a multitude of health issues including cardiovascular disease, elevated risk of diabetes and metabolic syndrome. While individual situations can vary greatly, increasing protein levels in the diet has been shown to be an effective way to help combat obesity (2).

One of the ways protein can affect daily calorie intake is through its ability to increase satiety. Although high carbohydrate meals can increase satiety acutely, meals higher in protein (20-30% of the total energy provided by the meal) have been shown to have a more prolonged effect on satiety.  According to a study by Westerterp-Plantenga et al., published in the British Journal of Nutrition, this feeling of satiety is attributed to the ability of protein to stimulate the release of glucagon-like peptide-1 (GLP-1). Specifically, GLP-1 mediates the so-called “ileal brake”, an inhibitory feedback mechanism which controls the motility of a meal through the gastrointestinal system, and thus slows gastric emptying (3), thus leading to the feeling of being “full.” Moreover, free amino acids are released into the bloodstream following a high protein meal, which can also enhance the feeling of fullness (4).

In addition to inducing satiety, a high protein diet has also been found to impact the body’s daily energy expenditure. Daily energy expenditure can be broken down into different categories.  Active expenditure is the most variable form and results from physical activity. Resting metabolic ratecomprises around 70% of one’s daily calorie use and doesn’t vary much. One of the variants in resting metabolic rate is the total weight of lean tissue (e.g. muscle) in the body (4). Lean tissue can be increased or maintained by engaging in regular resistance exercise and a consistent intake of protein and calories in daily meals (4).

Protein not only has the potential to affect long-term energy expenditure but can also affect calories burned directly after a meal (diet-induced thermogenesis), even more so than other macronutrients (5). This increase in diet-induced thermogenesis is partly due to an enhanced protein turnover rate.  When the body is flooded with more protein than it can handle, it actively oxidizes and eliminates the excess amino acids. This leads to an increase in thermogenesis and the resultant up-regulation of uncoupled protein-2 (UCP2) in the liver and uncoupled protein-1 (UCP1) in brown adipose tissue, in turn, leads to higher energy expenditure (5).  Protein is also an inefficient source of ATP compared to fat and carbohydrate, requiring several stages of metabolism, including urea synthesis, before becoming available for energy production. According to a recent study, up to forty-two percent of the observed increase in energy expenditure following a high-protein, carbohydrate-free meal can be explained by these additional steps and the increase in gluconeogenesis that follows (4).

The battle against obesity is a very complex, multi-faceted issue that includes hormonal balance, genetic makeup and metabolic processes, but evidence from recent and ongoing studies suggests that protein can play an important role in body weight management.

 

References:

1. Ogden C. L., Carroll, M. D., Kit, B.K., & Flegal K. M. (2014). Prevalence of childhood and adult obesity in the United States, 2011-2012. Journal of the American Medical Association, 311(8), 806-814.

2. Rodriguez, N., & Garlick, P. (2008). Introduction to protein summit 2007: Exploring the impact of high-quality protein on optimal health. The American Journal of Clinical Nutrition, 87, 1551-3.

3. Marathe CS, Rayner CK, Jones KL, Horowitz M. Effects of GLP-1 and incretin-based therapies on gastrointestinal motor function. Exp Diabetes Res. 2011;2011:279530.

4. Westerterp-Plantenga, M., Lemmens, S., & Westerterp, K. (2012). Dietary protein- its role in satiety energetics, weight loss and health. British Journal of Nutrition, 108, S105-S112.

5. Paddon-Jones, D., Matters, R., Wolfe, R., Astrup, A., & Westerterp-Plantenga, M. (2008). Protein, weight management, and satiety. The American Journal of Clinical Nutrition, 87.