Featured article in the Spring 2019 Issue of Nutrition Close-Up; written by Marie Spano, MS, RD, CSCS, CSSD
Healthy strong muscles are important throughout the lifespan.
Resistance training and sufficient dietary protein help support muscle maintenance and strength. Research has shown the importance of both the total amount of protein consumed each day as well as the amount of protein per meal. However, emerging research is showing other factors within food, besides protein, influence the synthesis of new proteins in muscle.
Over the past several years, scientists have examined how amino acids and isolated sources of protein impact muscle protein synthesis. This research serves as a foundation to better examine aspects beyond protein. Leucine, an essential amino acid, turns on the machinery driving the synthesis of new proteins in muscle. While leucine is the switch turning this process on, all essential amino acids are necessary to provide the building blocks for muscle protein synthesis to be running optimally. Quality sources of protein including whey, egg, soy and beef contain all essential amino acids in appreciable quantities to support this process. Yet studies comparing protein-rich drinks and whole foods have led to results that cannot be explained by differences in leucine or the amount of high quality protein consumed.
One recent study was designed to examine how protein, in its whole, natural state in the form of eggs, impacted muscle protein metabolic responses. Researchers took resistance-trained men and gave them either whole eggs or egg whites, each containing 18 grams of protein, after exercise. Both the whole eggs and egg whites turned on the synthesis of new proteins in muscle. However, whole eggs increased muscle protein synthesis to a greater extent than egg whites. In this study, the authors noted that differences between whole eggs and egg whites cannot be explained by leucine content, the appearance of leucine within the bloodstream, or variances in the muscle signaling pathway. Researchers suggest there may be something about the whole egg matrix, which consists of high-quality protein, fat, vitamins and minerals, that may support a greater response in muscle compared to the response seen with egg whites.
Whole foods that are good sources of protein, such as eggs, provide a package of nutrients that may lead to greater muscle protein synthesis than equal amounts of isolated protein. Whole foods have a unique food matrix that include not only protein, but also vitamins, minerals, fats and other compounds that cannot be deconstructed and isolated or put back together with the same result. As evidence mounts to support the benefits of non-protein food compounds or the synergistic action of compounds found in whole foods, consumers would be wise to follow the age-old advice from registered dietitians: eat more whole foods closer to the way these foods are found in nature.
Marie A. Spano, MS, RD, CSCS, CSSD, is a nutrition communications expert and one of the country’s leading sports nutritionists. Spano has appeared on CNN as well as NBC, ABC, Fox and CBS affiliates, and authored hundreds of magazine articles and trade publication articles. She is lead author of the textbook Nutrition for Sport, Exercise and Health and co-editor of the NSCA’s Guide to Exercise and Sport Nutrition (Human Kinetics Publishers).