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Muscle quality: what does it mean to your health?

Featured article in the Winter 2016 Issue of Nutrition Close-Up; written by Christian Wright, Doctoral Student, Purdue University

“Bigger is better” for most Americans when it comes to skeletal muscle. One only needs to look at the latest cover of health magazines for headlines such as “build muscle fast” and “supersize your legs” to know this to be true. After all, a larger muscle is generally a stronger muscle, which is important for overall health. In fact, muscular strength is often used as a surrogate for one’s physical health as it is independently associated with not only mobility, but also the development of chronic disease.

Continue reading “Muscle quality: what does it mean to your health?”

Underfueling: are we taking weight loss too far?

Featured article in the Fall 2015 Issue of Nutrition Close-Up; written by Pamela Hernandez, CPT

The Female Athlete Triad is most often associated with high school or collegiate athletes, but its symptoms can affect women of any age who engage in high levels of physical activity and eat a very low-calorie diet in an attempt to lose weight.  Continue reading “Underfueling: are we taking weight loss too far?”

Do Eggs Make a Healthy Pairing with Resistance Exercise?

022048480-egg-holds-dumbbell-300x300-300x220Egg or bagel breakfast both showed neutral effects on blood lipids among untrained individuals put on a 12-week training schedule.

A high quality source of protein like eggs sounds like a logical pairing with resistance training to build lean body mass, but may lead some to question what effect eggs may have on cardiovascular risk factors, like blood lipids (Clayton, 2015).

Continue reading “Do Eggs Make a Healthy Pairing with Resistance Exercise?”

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.

Leucine: Promoting Muscle Anabolism at Breakfast

Muscle Illustration

Protein is a critically important fuel source for muscles, and branched chain amino acids (BCAAs) are particularly so. Leucine is the most abundant BCAA found in muscles, and as the body of leucine research continues to grow, so does the evidence pointing to several benefits that leucine imparts, including the regulation of skeletal muscle protein synthesis. This was demonstrated in a study where leucine supplementation in a low dose of whey protein stimulated postprandial human myofibrillar protein synthesis as effectively as a much greater dose of whey protein (1). Similarly, a low-protein mixed macronutrient beverage supplemented with a high amount of leucine was found to be as effective as a high-protein beverage at stimulating muscle anabolism (2). Furthermore, results of another study on muscle recovery suggest that increasing the concentration of leucine in an essential amino acid supplement during moderate intensity exercise may increase post-exercise skeletal muscle metabolism (3). In addition to tissue protein synthesis, leucine in combination with vitamin B6 also increased fat oxidation and insulin sensitivity and reduced oxidative and inflammatory stress, thus suggesting a potential approach in the management of obesity (4).

Leucine-3D

Leucine is an essential amino acid, and as such, it must be obtained from dietary sources, since our bodies cannot produce it. Animal proteins in general are among the best sources of dietary leucine. Eggs contain 1.086g of leucine per 100g weight, which translates to approximately 9% of its total protein content (5). When compared to other foods commonly consumed for breakfast, eggs are not as high on a gram for gram basis as oats or cheese (see figure below). However, when a comparison of leucine content is made on a per calorie basis, eggs come out looking better than most other common food sources. At only 72 calories, with 6.3 grams of protein and a high leucine content, eggs are a nutritionally- and protein-dense food source, perfect for those trying to get a little more protein, leucine and other essential micronutrients in their diets.

Charts_Leucine-in-Breakfast-Protein

As noted in the dialogue from the recent fourth meeting of the Dietary Guidelines Advisory Committee, protein is notoriously under-consumed at breakfast. Given their robust nutrient profile and leucine content, eggs can be an easy fix to this nutritional shortcoming and an important protein source to consider when helping patients and clients build healthful diets.

References:

  1. Churchward-Venne TA, Burd NA, Mitchell CJ, West DW, Philp A, Marcotte GR, Baker SK, Baar K, Phillips SM. Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men. J Physiol. 20012; 590(Pt 11):2751-65.
  2. Churchward TA, Breen L, Di Donato DM, Hector AJ, Mitchell CJ, Moore DR, Stellingwerff T, Breuille D, Offord EA, Baker SK, Phillips SM. Leucine supplementation of a low-protein mixed macronutrient beverage enhances myofibrillar protein synthesis in young men: a double-blind, randomized trial.Am J Clin Nutr. 2014; 99(2):276-86.
  3. Pasiakos SM, MClung HL, McClung JP, Margolis LM, Andersen NE, Cloutier GJ, Pikosky MA, Rood JC, Fielding RA, Young AJ. Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis. Am J Clin Nutr. 2011; 94(3):809-18.
  4. Zemel MB, Bruckbauer A. Effects of a leucine and pyridoxine-containing nutraceutical on fat oxidation, and oxidative and inflammatory stress in overweight and obese subjects. Nutrients. 2012; 4(6):529-41.
  5. USDA National Nutrient Database for Standard Reference. U.S. Department of Agriculture, Agricultural Research Service, USDA Nutrient Data Laboratory Website. Updated Dec 7, 2011.http://ndb.nal.usda.gov/. Accessed July 28, 2014.