The egg has been much maligned over the years with the popularity of low-fat diets. Recently, a nutrition conference entitled, "Where Would We Be Without the Egg? A Conference About Nature's Original Functional Food", was held and the abstracts of the presentations were published as a supplement to the October issue of the Journal of the American College of Nutrition.
Here, we present a summary of some of the important information presented.
Where Would We Be Without the Egg?
Dr. Clare M. Hasler, Ph.D, of the University of Illinois gave a presentation entitled, "The Changing Face of Functional Foods", in which she defines 'functional foods' as " ... those providing health benefits beyond basic nutrition and include whole, fortified, enriched or enhanced foods which have a potentially beneficial effect on health ... "
She notes that "eggs have not traditionally been regarded as a functional food, primarily due to concerns about their adverse effects on serum cholesterol levels." However, "it is now known that there is little if any connection between dietary cholesterol and blood cholesterol levels ... " she states.
In addition, Dr. Hasler notes that " ... eggs are an excellent dietary source of many essential (e.g., protein, choline) and non-essential (e.g., lutein/zeaxanthin) components which may promote optimal health."
In a presentation entitled, "Beyond the Zone: Protein Needs of Active Individuals", Dr. Peter W.R. Lemon, Ph.D. of the Exercise Nutrition Research Laboratory at the University of Western Ontario, addresses the important nutritional issue of protein.
He notes that although there has been debate and disagreement for centuries regarding human needs for dietary protein, recent scientific data seems to indicate that physically active individuals have significantly higher daily protein requirements. As a matter of fact, protein requirements may be increased by perhaps as much as 100 percent or more in very active vs. sedentary individuals. These needs have been calculated to be, on average, as follows:
- Sedentary - 0.8 grams of protein per one kg of body weight
- Physically Active - 1.6 to 1.8 grams of protein per one kg of body weight
Therefore, Dr. Lemon’s official recommendations for protein intake should be adjusted upwards for physically active people, particularly those people with higher needs for protein such as:
- Children and adolescents
- People with muscle disease-induced weakness
Lastly, Dr. Lemon notes that most physically active people who consume a varied diet that includes complete protein foods (animal products), can get enough protein from their diets, with no need for taking any protein supplements.
While most people associate carotenoids with vegetables, eggs are actually a very good source of lutein and zeaxanthin, which are yellow or orange carotenoids known as xanthophylls, according to Suzen M. Moeller, MS, and colleagues at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.
These carotenoids are known to accumulate in the eye lens and macular region of the retina, where concentrations are the highest.
Some research has suggested that these carotenoids may protect the eyes. This may be due to the ability of these substances to protect the eye from damage caused by ultraviolet light by quenching reactive oxygen species.
Studies have shown that high dietary intake of lutein and zeaxanthin is associated with a significant reduction in the risk for:
- Cataract (up to 20 percent reduction)
- Age-related Macular Degeneration (up to 40 percent reduction)
Other good sources of lutein and zeaxanthin are green vegetables such as spinach and broccoli.
The importance of the essential nutrient choline and the egg's potential to supply it, was the subject of a presentation by Dr. Steven H. Zeisel, MD, PhD, of the School of Public Health, School of Medicine, University of North Carolina at Chapel Hill, North Carolina, entitled "Choline: Needed For Normal Development of Memory."
"Choline is a dietary component essential for normal function of all cells," states Dr. Zeisel, noting that eggs are an excellent dietary source of choline.
- It is responsible for the structural integrity and signaling functions of cell membranes.
- It is the major source of methyl-groups in the diet (one of choline's metabolites, betaine, participates in the methylation of homocysteine to form methionine)
- It directly affects nerve signaling, cell signaling and lipid transport/metabolism.
In 1998, the National Academy of Sciences, USA, issued a report identifying choline as a required nutrient for humans and recommended daily intake amounts.
In addition, during pregnancy and breastfeeding, choline may be required in greater quantity as the mother's reserves are depleted. This is critical, because the availability of choline for normal brain development is critical.
In experimental rats, newborn rats who received choline supplements, either in utero or during the second week of life, showed improved brain functioning and greater lifelong memory capabilities, probably due to changes in the development of the memory center (hippocampus) in the brain.
According to Dr. Zeisel, "the mother's dietary choline during a critical period in brain development of her infant influences the rate of birth and death of nerve cells in this center." "These changes are so important that we can pick out the groups of animals whose mothers had extra choline even when these animals are elderly."
In other words, if the same association holds true in humans, this means that the memory capacity of an adult is greatly influenced by the diet that his mother ate during her pregnancy.
Dr. Zeisel notes that this critical need for choline during early brain development and is very similar to the need for folate during early gestation as well. "If folate isn't available in the first few weeks of pregnancy, the brain does not form normally," he states.
Therefore, he stresses that pregnancy is a critical period during which special attention has to be paid to ensure adequate dietary intake of various nutrients.
Demonization of the Egg
The cause of recent declines in egg consumption can be traced back to a "food scare" that began all the way back in the 1960s, according to Dr. William. Alex McIntosh, PhD, of the Department of Rural Sociology, Texas A&M University, who gave a presentation entitled, "The Symbolization of Eggs in American Culture: A Sociologic Analysis".
Using the Reader's Guide to Periodical Literature, the frequency of articles about eggs, dietary cholesterol and heart disease in popular magazines was obtained. An analysis was performed on the content of a random sample of these articles and it was discovered that the increasing trend of negative articles about eggs and public statements by groups such as the American Heart Association linking eggs, blood cholesterol and heart disease is associated with the decline in egg consumption.
Dr. McIntosh concludes that "public exposure to negative messages about particular foods can contribute to a decline in their consumption" and therefore exposing the public to more positive messages about foods can bring about an increase in the consumption of those foods.
The Cholesterol Issue
Do eggs adversely affect cholesterol levels? Most people would answer, "yes" without even thinking twice. However, this seems to be a popular misconception not supported by the evidence, according to Dr. Donald J. McNamara, PhD, of the Egg Nutrition Center, in Washington, DC, who made a presentation entitled, "The Impact of Egg Limitations on Coronary Heart Disease Risk: Do the Numbers Add Up?"
According to Dr. McNamara:
For over 25 years eggs have been the icon for the fat, cholesterol and caloric excesses in the American diet, and the message to limit eggs to lower heart disease risk has been widely circulated. The "dietary cholesterol equals blood cholesterol" view is a standard of dietary recommendations, yet few consider whether the evidence justifies such restrictions.
He notes that studies demonstrate that dietary cholesterol increases both LDL and HDL cholesterol with essentially no change in the important LDL: HDL cholesterol ratio.
For example, the addition of 100 mg cholesterol per day to the diet increases LDL cholesterol by 1.9 mg/dL, but that is accompanied by a 0.4 mg/dL increase in HDL cholesterol.
This, on average, means that the LDL: HDL ratio change per 100 mg/day change in dietary cholesterol is from 2.60 to 2.61, which is likely not even statistically significant and would probably have no influence on heart disease risk.
This helps to " ... explain the epidemiological studies showing that dietary cholesterol is not related to coronary heart disease incidence or mortality," concludes Dr. McNamara.
The Egg's Role in the Current American Diet
Despite the decline in egg consumption, they still make " ... important nutritional contributions to the American diet," according to Dr. Won O. Song, PhD, and Jean M. Kerver, MS, of the Food and Nutrition Database Research Center, Department of Food Science and Human Nutrition, Michigan State University. They explored this issue during their presentation entitled, "Nutritional Contribution of Eggs to American Diets."
The researchers used data from the most recent National Health and Nutritional Examination Survey (NHANES III, 1988-94) to compare the nutritional intake of diets that contained eggs with those that did not.
Nutrient intake, egg intake, socio-demographic data and blood cholesterol levels of over 27,000 subjects were grouped according to the occurrence and frequency of egg consumption.
Daily nutrient intake of people consuming eggs was significantly greater than non-egg eaters for all nutrients studied, except dietary fiber and vitamin B6. BOLD4
In the egg group, eggs contributed < 10 percent of the daily intake of:
10 percent to 20 percent of:
- Total, Saturated and Polyunsaturated Fat
20 percent to 30 percent of:
- Vitamin A
- Vitamin E
- Vitamin B12
Non-egg eaters had higher rates of inadequate intake for:
- Vitamin B12 (10 percent vs. 21percent)
- Vitamin A (16 percent vs. 21 percent)
- Vitamin E (14 percent vs. 22 percent)
- Vitamin C (15 percent vs. 20 percent)
They also note that dietary cholesterol was not related to serum cholesterol concentration. As a matter of fact, people who reported eating four eggs a week had a significantly lower mean serum cholesterol concentration than those who reported eating one egg a week. (193 mg/dL vs. 197 mg/dL).
The authors conclude that eggs make " ... important nutritional contributions to the American diet."
Journal of the American College of Nutrition October, 2000 (Supplement)