Protein
Eggs are an important source of high quality protein. On the evaluation scale most commonly used for assessing protein, egg protein is at the highest point, 100, and is used as the reference standard against which all other foods are assessed. This is because of the essential amino acid profile and the high digestibility of egg protein. When assessed against a range of different measures of protein quality (protein digestibility corrected amino acid score; biological value; net protein utilisation; protein efficiency ratio; protein digestibilty) eggs rank consistently high, even against other high quality sources of protein such as beef and cows’ milk [1].
12.6% of the weight of the edible portion of the egg is protein and it is found in both the yolk and the albumen. Although protein is more concentrated around the yolk, there is in fact more protein in the albumen.
As people age, the loss in muscle mass and strength (sarcopenia), increases in parallel to the rise in body fat. It had been argued that these changes in body composition are related to a decline in physical activity [2], but this view has been challenged by research suggesting that poor protein intake and changes in the body’s ability to utilize amino acids with age may also contribute to sarcopenia [3, 4]. Therefore it is possible that an adequate intake of high quality protein from sources such as eggs could help to prevent the degeneration of skeletal muscle in older people.
Egg protein is a rich source of the essential amino acid leucine, which is important in modulating the use of glucose by skeletal muscle and in facilitating muscle recovery after exercise. It has therefore been postulated that this would be advantageous to people undergoing endurance training [1].
In comparison with other high protein foods, eggs are a relatively inexpensive source of protein [5].
References
- Layman KL, Rodriguez NR. Egg protein as a source of power, strength and energy, Nutrition Today, 44, 1, 2009
- Joint WHO/FAO/UNU Expert Consultation Protein and amino acid requirements in Human Nutrition, WHO Technical Report Series 935, Geneva, 2002
- Wolfe RR. The underappreciated role of muscle in health and disease, American Journal of Clinical Nutrition 84,475-82 2006
- Thalacker-Mercer A E, Fleet J C, Craig B A, Carnell N S, Campbell W W. Inadequate protein intake affects skeletal muscle transcript profiles in older humans, American Journal of Clinical Nutrition, 85, 1344-1352, 2007
- Ruxton C. New evidence and recommendations for the use of eggs in the diet, Nursing Standard, 19 May 2010.
All information checked by an independent Registered Nutritionist/Dietitian