High-quality proteins make a valuable contribution to the synthesis and maintenance of muscle and indirectly to the regulation of blood glucose levels, thus contributing to power, strength, and energy. Eggs have traditionally been used as the standard of comparison for measuring protein quality because of their essential amino acid (EAA) profile and high digestibility. They provide a nutrient-dense source of energy from protein and fat, approximately 75 kcal per large egg, as well as several B vitamins, including thiamin, riboflavin, folate, B12, and B6, which are required for the production of energy by the body. Given the unique complementary relationship between the EAA leucine and glucose utilization by muscle, it would follow that a diet rich in the amino acid leucine would be advantageous to men and women undergoing endurance training. Leucine is also a critical element in regulating muscle protein synthesis and may be the key amino acid defining the increased needs for EAA to optimize skeletal muscle mass. Increased tissue levels of leucine combine with circulating insulin to allow skeletal muscles to manage protein metabolism and fuel selection in relation to diet composition. Moreover, muscle recovery from exercise, both resistance and endurance, seems to be dependent on dietary leucine. Because eggs are an excellent, nutrient-rich source of leucine, as well as other EAAs, these protein-related benefits may be important to active individuals who routinely consume eggs as part of a varied, balanced diet
Do eggs deserve a second look?
Donald K. Layman, PhD, is a professor emeritus at the Department of Food Science and Human Nutrition at the University of Illinois. Dr Layman's research focuses on protein and amino acid requirements, and his work has helped to define roles of the branched-chain amino acids in skeletal muscle metabolism.
Nancy R. Rodriguez, PhD, RD, CSSD, FACSM, is an associate professor of Nutritional Sciences, University of Connecticut Sports Nutrition Programs at the University of Connecticut. Dr Rodriguez is actively involved in research on the relationships between exercise, protein intake, and protein utilizations in different population groups.
Corresponding author: Donald K. Layman, PhD, University of Illinois, 437 Bevier Hall, 905 South Goodwin, Urbana, IL 61801 (firstname.lastname@example.org).