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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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.

Continue reading “Can culinary medicine succeed where diet drugs don’t?”

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.

The Link Between Nutrition, Exercise and Muscle

lab-scientist-stock-photoENC 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. Brianna L. Neumann graduated from Truman State University with a bachelor of science in Exercise Science.  Her undergraduate research experience involved sports nutritional research, which began her desire to continue her education to focus on protein’s metabolic effect in the body.  She currently is a Master’s student at the University of Arkansas in the Department of Food Science, where her research specifically focuses on the impact protein quality and quantity on whole body energy metabolism.

In today’s society, big muscles are associated with weight lifting, men and sports. However, for most people, the benefits of gaining muscle mass include improvement in gross motor skills and a potential decrease in sarcopenia (gradual age-related loss in muscle mass and function). When discussing the building of muscle mass, a term you need to be familiar with is muscle protein synthesis (MPS). In general, in order to gain muscle mass, you need to synthesize more muscle than your body is breaking down. Through extensive research on muscle mass, it is known that an outside stimulus, such as resistance exercise, is required for building muscle. More recently, it has been discovered that nutrition, specifically in the form of protein, also plays a vital role in the physiology of this process5, 6.

Research has shown that consumption of high-quality proteins (e.g. beef; eggs) can stimulate MPS in both young and elderly individuals, following a meal8, and this effect may be attributed particularly to the quality – not just the quantity – of the protein. High-quality proteins tend to be from animal sources and include eggs, poultry, beef and dairy, which are high in essential amino acids (EAA), particularly the branched-chain amino acid leucine. Data show that leucine promotes MPS at a greater rate than that of the other EAA due to leucine’s ability to activate the mammalian target of rapamycin (mTOR), the key regulatory pathway in MPS1, 3.

A recent study clearly demonstrates the relationship between EAA and MPS. Eight individuals were given 10 grams of EAA on two separate occasions and a dose of rapamycin (an inhibitor of mTOR) on one occasion, which led to a 60% increase in MPS following ingestion of EAA.  However, this effect was completely blocked when subjects were treated with rapamycin4. In addition, another study tested 8 healthy, sedentary older adults with diets supplemented by leucine for 2 weeks (4 grams per meal) and found a significant increase in muscle fractional synthesis rate at the end of the treatment period4.  The muscle fractional synthesis rate is the fraction of the proteins that are synthesized in the muscle per unit of time9.

Resistance exercise can also increase MPS and add “bulk,” or increase muscle mass. There are two primary principles of exercise that need to occur in order for someone to successfully add “bulk”: progression and overload. The most important for MPS is overload, defined as placing additional stress on a muscle above normal conditions, and includes exercises such as weight lifting and swimming. Therefore, in order for someone to “bulk up,” they must have an outside stimulus that serves to initiate MPS inside the body. There are various ways to achieve overload such as adding more weight or increasing a swimming distance, and research is still being done regarding how to maximize MPS. A recent study examined the effect of concentric resistance exercise on 8 trained men2 to determine if muscle building signaling enzymes were progressively increased as more sets of resistance activity were performed. The investigators concluded that performing additional sets showed a greater increase in MPS than just a single set of lifts.

Is there an additive effect of protein ingestion and resistance exercise? As stated above, both exercise and nutrition initiate MPS, and ideally, one would have both in order to maximize muscle building within the body. For example, the effect of beef ingestion coupled with resistance exercise was recently tested in 35 middle-aged men who consumed one of four different amounts of beef (0, 57, 113 and 170 grams) prior to resistance exercise (unilateral movements). Results of this study demonstrated that eating 170 grams of beef in addition to exercise significantly elevated MPS when compared to the other groups7.

In summary, MPS is complex and can be influenced by both nutrition and exercise. Both can activate MPS individually, but research shows combining the two is best to promote MPS. Further research is still needed to understand the long-term impact of this combination, as well as the practicality of dietary intake for individuals in order to maintain and increase muscle tissue.

Cited:

  1. Anthony JC, Yoshizawa F, Anthony TG, Vary TC, Jefferson LS, Kimball SR. Leucine stimulates translation initiation in skeletal muscle of postabsorptive rats via rapamycin sensitive pathway. Journal of Nutrition. 2000; 130(10): 2413-9.
  2. Burd NA. Holwerda AM, Selby KC, West DW, Staples AW, Caine NE, Cashaback JG, Potvin JR, Baker SK, Phillips SM. Resistance exercise volume affects myofibrillar protein synthesis and anabolic signaling molecule phosphorylation in young men. Journal of Physiology. 2010; 588(Pt 16): 3119-30.
  3. Caperson SL, Shelffield-Moore M, Hewlings SJ, Paddon-Jones D. Leucine supplemenatation chronically improves muscle protein synthesis in older adults consuming the RDA for protein.Clinical Nutrition. 2012; 31(4): 512-519.
  4. Dickson JM, Fry CS, Drummond MJ, Gundermann DM, Walker DK, Glynn EL, Timmerman KL, Dhanani S, Volpi E, Rasmussen BB. Mammalian target of rapamycin complex 1 activation is required for the stimulation of human skeletal muscle protein synthesis by essential amino acids.The Journal of Nutrition. 2011; 141(5): 856-62.
  5. Drummond MJ, Rasmussen BB. Leucine-enriched nutrients and the regulation of mammalian target of rapamycin signaling and human skeletal muscle protein synthesis. Current Opinion in Clinical Nutrition and Metabolic Care. 2008; 11(3): 222-6.
  6. Millward DJ, Layman DK, Tomé D, Schaafsma G. Protein quality assessment: impact of expanding understanding of protein and amino acid needs for optimal health. American Journal of Clinical Nutrition. 2008; 87 (5): 1576S-1581S.
  7. Robinson MJ, Burd NA, Breen L, Rerecich T, Yang Y, Hector AJ, Baker SK, Phillips SM. Does-dependent responses of myofibrillar protein synthesis with beef ingestion are enhanced with resistance exercise in middle-aged men. Applied Physiology, Nutrition, and Metabolism. 2013; 38 (2): 120-5.
  8. Symons TB, Sheffield-Moore M, Wolfe RR, Paddon-Jones D. A moderate serving of high quality protein maximally stimulates skeletal muscle protein synthesis in young and elderly subjects.Journal of American Dietetics Association. 2009; 109(9):1582-6.
  9. Wolfe RR. Skeletal muscle protein metabolism and resistance exercise. The Journal of Nutrition. 2006; 136(2): 525S-528S.