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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."
Protein
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
- Dieters
- Vegetarians
- People with muscle disease-induced weakness
- Elderly
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.
Carotenoids
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.
Choline
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:
- Folate
- 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)
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