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W HAT is meant by protective foods?
Why are eggs, dairy products, fruits
and vegetables considered protective
foods rather than sugar, lard or high patent
flour? The answer is simple.
During the past 20 years great progress
has been made in nutrition research, especially
regarding the importance of proteins, minerals
and vitamins. We know that the highly
refined foods such as sugar and white
flour have lost a large part of their vitamin
and mineral content during the process of
manufacture. Since they constitute a large
part of the average diet, liberal quantities
of the protective foods especially rich in the
necessary vitamins, minerals and proteins
must be used to balance the diet. It is the
high vitamin, mineral or protein content that
characterizes protective foods.
By way of an example, an analogy may be
drawn between the automobile engine and
man. The engine uses gasoline for fuel ;
man largely uses carbohydrates and fats for
by R. V. BOUCHER*
Pennsylvania State College
fuel. The spark plug is necessary to explode
the gasoline thus releasing the energy for
power to move the car. Vitamins play a
similar role in man; vitamin Bl> for example,
acts as one of the spark plugs in the human
engine making the energy in starchy foods
available for use by the body. Other vitamins
perform equally important functions.
Minerals in protective foods play roles
that are just as important as those of the
vitamins. Thus, calcium and phosphorus are
used to build strong bones and sound teeth .
Iodin~ is n~eded to permit normal thyroid
functwn, wtthout which goiter results. Iron
and copper are necessary for hemoglobin
*Dr. Boucher presented this paper at the Poultry Field
Day of the New ) ersey College of Agriculture ) une 12
194 1. For the quantitative values employed in his talk '
Dr. ~ o u ch e r drew freely upon current literature. As th ~
maten al w~s _p rese nted as a talk, Dr. Boucher did not indude
a bi)>llography of the scientific literature used in
tts preparat1on.
(Reprinted from The U . S. Egg & Poultry Magazine 47 (1 94 1) 470-473, 512.)
Distributed by the
POULTRY AND EGG NATIONAL BOARD
308 West Washing ton Stree t, Chicago, Illinois
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regeneration and if these are deficient one
type of anemia is certain to develop.
The yolk is composed of:
Water - 49.0 per cent
Fat - 31.6 per cent
Protein - 16.7 per cent
Ash - 1.5 per cent
The yolk differs widely in composition
Proteins are used by the body in many
ways, chief among which are the growth
and repair of organs and muscle tissue. To
be of greatest value to the body, proteins
must be of high biological value, that is,
composed of the proper combination of essential
amino acids.
In thinking of proteins it is helpful to
visualize the protein as a brick wall and
the amino acids as the bricks which are
placed on top of each other to form the wall.
There are 20 some different amino acids,
about half of which are essential in nutrition.
If a protein is composed of the proper proportion
of these essential amino acids it is
then said to be of high biological value.
from the white, since its purpose is to supply
nutritive material for the developing chick.
It contains much less water and more solid
materials, and is well fortified with vitamins
and minerals.
Why are eggs classified as protective
foods? A look inside the shell will furnish
the answer. There we find the white weighing
58 per cent, the yolk 31 per cent, leaving
the shell to account for the remaining 11
per cent.
As we all know, the yolk and the white
are guite different in appearance and composition.
The white contains:
Water - 87.8 per cent
Protein 10.0 per cent
Ash - 0.8 per cent
Carbohydrate - 0.5 per cent
Fat - 0.05 per cent
The proportion of water is high, since it
serves as the principal reservoir for the
embryo during incubation.
Since the shell is not used for human
food, its composition will be mentioned
only to say that it is largely calcium carbonate
- 93.7 per cent.
The percentage composition of the yolk
and white combined is about:
Water - 73.7 per cent (37.0 grams)
Protein - 13.4 per cent ( 6.7 grams)
Fat 10.5 per cent ( 5.2 grams)
Ash 1.0 per cent ( 0.5 grams)
Carhohvdrate - 0.3 per cent ( 0.15 g rams)
The figures in parentheses represent the
approximate weight of the constituents contained
in an average size egg. These values
emphasize the high efficiency of the modern
hen as manufacturer of human food.
The 1 per cent ash contained in the egg is
composed of the following chemical elements,
expressed as percentage and as grams
of the edible portion of an average size egg:
Calcium 0.060000 per cent 0.030000 gram
Chlorine 0.130000 per cent 0.065000 gram
Copper 0.000187 per cent 0.000094 gram
Incline · 0.000010 per cent 0.000005 gram
Iron 0.003100 per cent 0.001550 gram
Magnesium 0.050000 per cent 0.025000 gram
Manganese 0.000033 per cent 0.000017 gram
DAILY ADULT REQUIREMENTS OF ESSENTIAL NUTRIENTS
Nutrients Daily Requirements
of an Average Adult
Protein ................. . 70 grams ....................................... .
Calcium ............... . 0.8 gram ......................................... .
Iron ..................... . 12 milligrams ............................... .
*Phosphorus ......... . 1.30 grams ..................................... .
*Iodine ................. . 0.1 milligram ................................. .
Vitamin A 5000 International Units ............... .
Vitamin B, ........... . 2 milligrams ................................... .
Vitamin C ........... . 75 milligrams ····················· --·-·-·····
Rihoflavin ............. . 3 milligrams ................................... .
N;cotinic acid ....... . 20 milligrams ................................. .
*Vitamin D ......... . about 400 International Units ... .
Gram = 15.43 grains
Milligram = 1/1000 gram
Microgram = 1/1,000,000 gram
What ONE EGG Furnishes
in the Daily Diet
6.7 grams
0.03 gram
1.55 milligrams
110 milligrams
. 005 milligram
200 to 800 International Units
20 to 40 International Units
none
I 00 to 200 micrograms
about 760 'micrograms
10 to 50 International Units
or 4
or 3
or 3
or 3
or 3
or 10%
or 4%
or 13%
or 9%
or 5%
to 16%
to 6%
to 7%
to 4%
to 12%
•Daily requirements for phosphorus, iodine and vitamin 0 1 not included in recommendation of Committee on Foods
and Nutrition of the National Research Council and Coun< il of Foods of the American Medical Association .
SPECIAL COLLECTIONS &: RARB BOOKS
WALTER CLINTON jACKSON LIBRARY
TH!! UNIVERSITY OF NORTH CAROLINA AT GREENSBORO
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Gift of Paul and janice Hessling
Phosphorus
Potassium
Sodium
Sulfur
0.220000 per cent 0.110000 gram
0.140000 per cent 0.070000 gram
0.130000 per cent 0.065000 gram
0.183000 per cent 0.091500 gram
Smaller quantities of other elements such as
zinc, silver, aluminum, tin and lead are also
present. These values are not absolute for
the mineral content of the egg varies to some
extent depending upon the feed and the condition
of the hen.
The vitamin content of eggs also varies
with the ration fed the hen. The average
fresh egg, however, will contain from 200 to
800 International Units of vitamin A; 10 to
50 International Units of vitamin D; 20 to
40 International Units of Vitamin B1 , now
known as thiamin; 100 to 200 micrograms
of riboflavin; and 600 to 1200 micrograms
of pantothenic acid, concentrated largely in
the yolk. Vitamin E, vitamin K and nicotinic
acid are known to be present, although
in relatively smaller amounts. Vitamin B6
is also thought to be present; however, quantitative
measurements of its concentration in
the egg have not been reported.
Now that we know how much of the
protective food factors an egg contains, let
us consider the value of an egg as protective
food in a man's diet. In order to do
this it is necessary to review the human
requirements for the better known nutritive
essentials.
Nutrients Required in Daily Diet
The Committee on Foods and Nutrition
of the National Research Council and the
Council on Foods of the American Medical
Association have reached a tentative agreement
on the daily requir~ments of man for
the following specific nutrients :
Protein
Calcium
Iron
Vitamin A
Vitamin B,
Vitamin C
Riboflavin
Nicotinic acid
Vitamin D
70 grams
0.8 gram
12 milligrams
5,000 International Units
2 milligrams
75 milligrams
3 milligrams
20 milligrams
Unknown
These values are for an average size adult
man who exercises to a medium degree.
They do not apply to men at hard labor nor
to invalids. Likewise, requirements vary for
infants and children of different ages and it
is known that about 400 International Units
of vitamin D per day are required for pregnant
and lactating women and for children.
If our present knowledge of nutrition was
generally applied so that all the people in
the United States were fed according to these
standards, two important results would be
accomplished. First, the health and vigor
of the people would be greatly increased,
resulting in smaller doctor and hospital bills,
less loss of working time, greater efficiency
and longer life. Second, from the standpoint
of agriculture, there would no longer
be a surplus of food products. . In fact it
would be necessary to increase the production
of fruits, succulent vegetables and dairy and
poultry products. This would mean more
cows and more chickens which would in
turn require more feed.
Since the approximate requirement of man
for some of the more important essential
nutrients is known, let us consider what part
of this requirement is supplied by one egg
per day. The following table gives the quantity
of these nutrients contained in an average
egg and the approximate percentages
of the daily requirement that this quantity
supplies.
Protein
Calcium
Iron
Vitamin A
Vitamin B,
Vitamin C
Riboflavin
Nicotinic acid
Vitamin D
6.7 grams
0.03 gram
1.55 milligrams
200 to 800
International Units
20 to 40
International Units
None
100 to 200 micrograms
About 760 micrograms
10 to 50
4
3
10%
4'7o
13%
to 16%
to 6%
3 to 7%
3 to 4%
International Units 3 to 12'/o
Thus, we see that a single egg supplies
from 3 to 16 per cent of the daily requirement
of all except one of the nine essential
nutrients that are most likely to be deficient
in the average human diet. The one exception
is vitamin C which is readily supplied
by tomatoes and citrus fruits. ·
It must be remembered, too, that · the
values we have been considering are only
the better known of the human requirements.
The egg occupies a unique place as
a food because it contains all the food elements,
known and unknown, that are required
to produce a perfect chick. This
covers a wide range and includes all of the
essential amino acids that go to form a perfect
protein, as well as all the minerals and
vitamins needed for embryonic growth. This
is quite a severe test, for embryonic growth
is both rapid and exacting in its requirements.
Ration Modifies Chemical Composition
The nutritive requirements of man and
of chicks are not identical but as far as is
known may be quite similar qualitatively.
In many instances the quantitative requirement
of the chick estimated on a body weight
basis is greater than that of man.
Another point that deserves discussion is
that one egg may differ from another in
both physical and chemical properties to an
extent which is of significance both commercially
and nutritionally. From the commercial
standpoint, variation in such physical
characteristics as strength of shell and
ratio of thick to thin white will determine
the capacity of the egg to withstand transportation
and storage; from the nutritional
standpoint changes in certain constituents,
which are measured in micrograms, will promote
or inhibit the normal process of development
in the embryo and influence the
value of the egg in the human. diet.
While the breed of the hen may affect to
some extent the composition of the egg,
there is ample evidence that the ration of
the fowl modifies the chemical composition
and, therefore, the nutritive value and hatchability
of the egg. A fairly good ration will
support egg production but it takes a high
grade ration to produce eggs that will give
high hatchability. The reason is that within
certain limits the composition of the egg
'depends upon the feed the hen receives.
An example of this is riboflavin which,
if present in the ration at a level of 600
micrograms per pound, will support high
e~g production but the eggs will not hatch.
If the riboflavin is increased to about 1 000
micrograms per pound of feed the eggs 'will
hatch well. It is obvious that the egg that
would hatch well because of its higher riboflavin
content would also be a more valuable
protective food when used in a human diet.
With regard to the other vitamins, it is
also known that the amounts of B11 E, K
and pantothenic acid in the egg are affected
by the ration.
The vitamin A potency of the egg can be
increased three to four-fold. It has been
shown that on practical type rations 11 to
32 per cent of the dietary intake of vitamin
A is deposited in the yolk.
Vitamin D is transferred to the egg even
more readily than vitamin A. In an experiment
where massive doses of vitamin D were
fed, the D content of the egg was increased
600 times resulting in a yolk that was truly
a vitamin D concentrate. In an experiment
using a practical type ration containing 1
per cent cod liver oil, it was found that 10
per cent of the vitamin D in the feed was
transferred to the egg. On this basis, the
hen evidently transmits dietary vitamin D
to the egg more efficiently than the cow
transfers it to milk since it was found that
only 2 per cent of the D in cows feed appeared
in the milk.
Thus we can say that the composition of
the hen's egg is not constant. This is important
since it affects the nutritional value,
hatchability and ability of the egg to stand
up under transportation and storage.
What wotJld be the effect if everybody
in the nation ate one egg per day? That
would be a total of 47,450 million eggs per
year, which is 10,818 million more eggs per
year than were prodtJced on the average during
the 1925-1937 period. To produce that
number of eggs would reqtJire an increase
of about 30 per cent in nation-wide egg production.
~~ ~ RICH IN VITAMIN 0 BUILD SOUND RICH IN ORGANIC IRON OOCTORS RECOMMEND EGGS PROTEIN FOR BODY.
TEETH BUILDING
