The slogan “Go to work on an egg” was used by the egg marketing board in the 1950s. The basis of the campaign was that having an egg for breakfast was the best way to start the working day. The egg marketing board was disbanded in 1971 and since then eggs have had some major bad press with worries about their cholesterol content in the 1970s and Salmonella in the 1980s. However, the health risks of dietary cholesterol have long since been disproved and a 2004 Food Standards Agency survey of 28,000 UK-produced eggs found that not one contain salmonella. Whats more the latest research backs the 1950s assertion that an egg or two may well be the best way to start the day.

The nutritional value of eggs

An egg contains everything you need to make a chick and because of that, it is one of the most nutritious foods there is.

PROTEIN

Eggs are an important source of high quality protein. 12.6% of the weight of the edible portion of the egg is protein and it is found in both the yolk and the white. Although by volume there is more protein in the white, protein content is more concentrated in the yolk.

The most common scale for assessing protein quality, the evaluation scale, uses egg protein as its reference standard against which all other foods are assessed and giving it the value 100. This is because egg is both a complete protein containing all essential amino acids and because the protein in cooked egg is highly digestible.  On all measures egg protein ranks consistently high on every scale, even against other high quality sources of protein such as beef, cows’ milk or Whey (1).

Protein in sport

Protein plays a key role in the adaptations that take place in response to training. Amino acids form the vital building blocks for the manufacture of new muscle tissue and for the repair of old or damage tissue. Research consistently shows that the quality and digestibility of protein is important for ensuring that active individuals build muscle strength.

However its not quite as simple as just eating good quality protein and building more and more muscle. Muscle is not static and is constantly being recycled. The benefit of animal protein diets appears to be in reduced protein breakdown giving a higher net protein synthesis relative to vegetable protein diets.

Egg protein is a rich source of the essential amino acid Leucine which is one of the three branched chain amino acids (BCAAs), and is unique in its ability to stimulate skeletal muscle protein synthesis. Leucine has been shown to activate the anabolic (muscle-building) pathway by stimulating the major complex mTOR (2,3,4). It is thought that decreasing leucine concentrations signal to mTOR that there is not enough dietary protein present to synthesize new skeletal muscle protein and increased leucine levels signal to mTOR that there is sufficient dietary protein to synthesize new skeletal muscle protein. mTOR then increases protein synthesis by stimulating the body to create new muscle tissue and increasing the amount that can be produced in a period of time (5).

There is also growing evidence that Leucine is also involved in modulating the use of glucose by skeletal muscle and in facilitating muscle recovery after exercise (1).

Satiety

The high-quality protein in eggs helps you to feel fuller longer and stay energised.

Studies, looking at typical UK breakfasts, the breakfasts have shown increased satiety, reduced hunger and a reduced desire to eat after an egg meal relative to both cereal and croissant breakfasts. The egg breakfast also resulted in a significantly lower energy intake (measured by weighed intake) at lunch relative to the cereal-based breakfast and at the evening meal when compared to a croissant-based breakfast (6,7)

VITAMINS AND MINERALS

ANTIOXIDANTS

There are increasing studies showing that dietary antioxidants may reduce oxidative stress and skeletal muscle damage associated with strenuous exercise (14) Eggs contain substances called lutein and zeaxanthin and the vitamins A, E and selenium, all of which have antioxidant functions. Eggs may therefore offer further nutritional advantages as part of an athlete’s diet.

Lutein and zeaxanthin have also been found to help prevent macular degeneration. Though eggs contain a small amount of these two nutrients, research shows that the lutein from eggs may be more bioavailable than lutein from other food sources (15). 

ADVICE

In the UK there is no official advice on how many eggs you should eat. 

Protein is an essential part of a young athlete’s diet, being responsible for building, maintaining and repairing muscle and other body tissue (17). Although research generally shows that protein intakes in the UK are adequate, it should be noted that inadequate caloric intake will cause a protein imbalance even if getting the recommended amount of protein (18). Young athletes need to consume enough calories each day match their training needs and keep protein stores in balance.

While it has been suggested that adult athletes may need more protein per pound of body weight than adults who are not athletes, additional protein needs have not been specifically evaluated for younger athletes. However, the American Diabetes Association (ADA) has issued the following daily recommendations (17):

• Athletes who have just begun a training program require 1.0–1.5 g/kg of protein.
• Athletes who participate in endurance sports require 1.2–1.4 g/kg.
• Vegetarian and vegan athletes should be counseled to ensure that adequate intake or protein is consumed from plant sources.
• Athletes need to consume sufficient calories each day to maintain protein balance.

Eating too much protein can lead to dehydration, weight gain and calcium loss. It is critical that young athletes monitor their daily protein intake, because there is already a risk of calcium deficiency.

Eggs are a particularly good food for young athletes as they contain good quantities of B vitamins, Selenium, Calcium and Iodine which may well be deficient. They also contain sodium, potassium, phosphorus, magnesium, chloride, iron, zinc, copper and Vitamin K.

ALLERGIES

Egg allergy is most common in infants under the age of twelve months and then becomes progressively less of a problem. It is estimated to affect between 0.5% – 2.5% of infants, ~30% of whom will be tolerant at 10yrs and ~70% by the time they are teenagers. Most people outgrow their egg allergy by the time they reach adulthood, although in some cases the egg allergy may persist into adult life. A recent analysis found that only 0.5% of young adults in the UK are sensitive to eggs (16). Those with other allergies, or with a family history of allergy, seem to be particularly vulnerable.

REFERENCES

(1)  Layman KL, Rodriguez NR. Egg protein as a source of power, strength and energy, Nutrition Today, 44, 1, 2009

(2)  Anthony, J. C., Yoshizawa, F., Anthony, T. G., Vary, T. C., Jefferson, L. S., & Kimball, S. R. (2000) Leucine stimulates translation inititation in skeletal muscle of postabsorptive rats via a rapamycin-sensitive pathway. J. Nutr. 130: 2413-2419.

(3) Crozier, S. J., Kimball, S.R., Emmert, S. W., Anthony, J. C., & Jefferson, L.S. (2005) Oral leucine administration stimulates protein synthesis in rat skeletal muscle. J. Nutr. 135: 376-382.

(4) Bolster, D. R., Crozier, S. J., Kimball, S. R., & Jefferson, L. S. (2002) AMP-activated protein kinase suppresses protein synthesis in rat skeletal muscle through down-regulated mammalian target of rapamycin (mTOR) signaling. J. Biol. Chem. 277: 23977-23980.

(5) Merrick, W. C., & Hershey, J. W. B. (2000) The pathway and mechanism of initiation of protein synthesis. In: Sonnenberg N, Hershey JWB, Mathews MB, editors. Translational control of gene expression. Cold Spring Harbor Laboratory Press.*

(6) Wilson L, Fallaize R, Gray J, Morgan L, Griffin B. Eggs at breakfast increase satiety and reduce the subsequent intake of energy at lunch and an evening meal relative to cereal or croissant-based breakfasts. University of Surrey. Presented at The Nutrition Society Winter Meeting 6th-7th December 2011.

(7) Fallaize R, Wilson L, Gray J, Morgan L M, Griffin B A (2012) Variation in the effects of three different breakfast meals on subjective satiety and subsequent intake of energy at lunch and evening meal.  European Journal of Nutrition 10.1007/s00394-012-0444-z.

(8) http://www.egginfo.co.uk/vitamins-and-minerals-egg-0

(9) Gibson et al (2011) Nutritional Status of Junior Elite Canadian Female Soccer Athletes. Int J Sports Nutr and Exerc Metab 21, 507-514

(10) Aerenhouts et al (2008) Nutritional Habits of Flemish Adolescent Sprint Athletes Int J Sports Nutr and Exerc Metab 18, 509-523).

(11) Williams MH (2004): Nutrition for Health, Fitness & Sports. Boston: McGraw-Hill 2004

(12) Buchman A, et al.(2000): The effect of lecithin supplementation on plasma choline concentrations during a marathon. Journal of the American College of Nutrition 2000, 19:768–70

(13)  Zeisel SH (2006). Choline: Critical role during fetal development and dietary requirements in adults. Annu Rev Nutr, 2006; 26:229-50.

(14) Applegate, E. Effective nutritional ergogenic aids. Int J Sports Nutr 9, 229-39 (1999)

(15) Chung HY, et al. Lutein bioavailability is higher from lutein-enriched eggs than from supplements and spinach in men. J Nutr. 2004; 134:1887-1893.

(16) http://www.egginfo.co.uk/egg-allergy-qas

(17) Nevin-Folino, N. 2003. Pediatric Manual of Clinical Dietetics (2nd ed.). The Pediatric Nutrition Practice Group. Chicago: American Dietetic Association.

(18) Thompson, J.L. 1998. Energy balance in young athletes.International Journal of Sport Nutrition, 8160–74.