of most of the carbohydrates in food. Practically all of the
fruits, and many of tiie vegetables, are rich in this form of
carbohydrate, but grapes contain more than any of the
other fruits, while sweet com, onions, and unripe potatoes
contain appreciable amounts.
Fructose. ā The second member of the monosaccharide
group is more or less associated with glucose in plant and
fruit juices, and is used like that substance for the produc-
tion of glycogen in the body. Eaten as such, or produced
as the result of digestive action upon cane sugar, fructose
is changed into glycogen, chiefly upon entering the liver, and
for this reason will not be found to enter largely into the
blood of the general circulation.*
Honey is the most abundant source of fructose in nature.
Galactose. ā This sugar, unlike the other members of
this group, is not found free in nature, but it is produced
as the result of hydrolysis of milk and sugar, either by
enz3anes or by acids. Like glucose and fructose, galactose
seems to promote the production of glycogen in the body.
ā¢"Chemistry of Food and Nutrition" (revised edition), by Sherman,
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10 DIETETICS FOR XURSES
Certain subetances known as galactosides, which are combi-
nations of galactose and some substances other than carbo-
hydrates, are found in the nerve and brain tissues of the
animal body.
Disaccharides. ā Of the second group of carbohydrates,
we are probably more familiar with sucrose, or cane sugar,
than with either of the other two, since it is in this form
that the greater part of the sugar eaten is purchased.
Sucrose. ā By far the greater part of the sugar entering
into the average dietary is manufactured from sugar and
sorghum canes, and from sugar beets; but appreciable quan-
tities are derived from the sugar maple and sugar palms.
Many of the sweet fruits are rich in this form of sugar; pine-
apples are said to contain at least half of their solids in
sucrose; and although other fruits and vegetables do not
contain so high a percentage of this sugar, oranges, peaches,
apricots, dates, raisins, prunes, carrots and sweet potatoes
contain goodly quantities, which are associated with glucose
and fructose. Sucrose is readily hydrolized, either by acids
or enzymes. The inverting enzyme (invertase) of yeast
and sucrose of the intestinal juice, convert sucrose to fruc-
tose and glucose, in which forms it is absorbed into the
portal blood. It is believed that when sucrose is eaten in
very large quantities, it is sometimes absorbed from the
stomach. In these cases it does not become available for
use in the body, but acts in the same manner as when in-
jected directly into the blood stream, being excreted un-
changed by way of the kidneys. According to Herter,
sucrose is much more susceptible to fermentation in the
stomach than either maltose or lactose; and since it has no
advantage over these sugars from a standpoint of nutrition,
they are frequently substituted for sucrose in cases where
the dangers arising from fermentation must be avoided.
Maltose (Malt sugar) is an important constituent
of germinating grains ā malt and malt products being
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FOOD 11
formed as the result of enzymic action (amylases) on starch.
A similar action takes place in the mouth as the result of the
ptyalin in the salivary juices and in the intestines from the
action of the starch splitting enzyme, amylopsin, in the
pancreatic juice. The maltose thus formed is further con-
verted into glucose by the sugar splitting enzyme in the
intestinal juice, and in this form it is chiefly absorbed.
Maltose is also an intermediate product formed during the
manufacture of commercial glucose as the result of the boil-
ing of starch with dilute acids.
Lactose (sugar of milk) is one of the most important
constituents in the milk of all mammals. In freshly
secreted human milk, lactose occurs in quantities rang-
ing from 6 to 7%, and in the milk of cows and goats from
4 to 5%. Lactose is much less soluble than sucrose, and
decidedly less sweet; hence, owing to this latter property,
as well as to its lack of susceptibility to fermentation, lac-
tose is frequently used to bring up the sugar content of
infant formulas to the desired percentage, and the diets
used in the abnormal conditions when additional energy
material is needed. During the process of digestion, lactose
is hydrolized by the lactase in the intestinal juice, yielding
one molecule of glucose and one of galactose. Like maltose,
little if any of this sugar is absorbed in its original form,
since experiments made with injections of lactose into the
blood result in the rapid and almost complete elimination
by way of the kidneys. No such results are obtained when
even large amounts of lactose are taken by way of the
mouth.
Polysaccharides. ā This group of carbohydrates is
complex in character, built up of many sugar molecules,
and upon digestion must be broken down into simple sugars
before they can be utilized by the body.
Starch is the form in which the plant stores her supply
of carbohydrates. It is found in this form in roots and
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12 DIETETICS FOR NURSES
(mature) tubers, three-fourths of the bulk of which is made
up of this material. From one-half to three-quarters of the
solids of grains is made up of starch also. Pure starch is a
fine white powder, odorless and almost tasteless. It is in-
soluble in cold water and alcohol, but changes from an insol-
uble substance to a more soluble one upon the application
of heat. Upon hydrolysis starch gives first a mixture of
dextrin and maltose, then glucose alone as an end product.
This hydrolysis may be the result of enzymic action, as
occurs upon bringing starch in contact with the ptyalin in
the saliva, or with the amylopsin in the pancreatic juice;
or it may be the result of boiling starch witii acid, as is seen
in the manufacture of commercial glucose.
Dextrin, as has already been stated, is an intermediate
product of the hydrolysis of starch by acid or enzymes.
Glycogen is the form in which the carbohydrates are
stored in the body, just as starch is the form in which they
are stored in plants. It is found in all parts of the body,
but is especially abundant in the liver. Here it is stored
in the cell substance rather than in the nucleus. The stor-
age of glycogen in the human body depends largely upon
the mode of life and upon the diet. Active muscular work,
especially out of doors, uses up the store of glycogen with
great rapidity; while rest and a sedentary life promotes
its storage. The body readily converts its supply of gly-
cogen into glucose, the form in which the body uses the
carbohydrates for fuel.
Cellulose is a woody, fibrous material insoluble in water
and to a certain extent impervious to the action of the
digestive enzymes. This carbohydrate constitutes the skele-
ton of plants just as the bones constitute that of the animal
body. It is probable that owing to the length of time re-
quired for this carbohydrate to be broken down in digestion,
much of it escapes oxidation entirely. Hence, it passes
down the digestive tract lending bulk to the food-mass and
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FOOD 13
thus promoting peristalsis throu^out the whole of the
digestive tract.
Organic Acids. ā Certain of the carbohydrate foods
(fruits and green vegetables) contain appreciable amounts
of organic acids or their salts; oranges and lemons, for
example, are rich in citric acid ; grapes contain considerable
quantities of potassium acid tartrate, apples and other fruits
have malic acid; many of the fruits have succinic acid;
a few foods contain oxalic acid, or oxalates. All of these
organic acids are burned in the body to produce energy,
with the possible exception of the oxalates, which seem to
have little, if any, food value. According to Sherman, these
organic acids have a lower fuel value, per gram, than carbo-
hydrates, but are reckoned as such in computing a food in
which they exist. The function of these acids is chiefly
liiat of neutralizing the acids formed in the body in metabol-
ism. Being base forming in character, they function after
absorption and oxidation in the body as potential bases ā
tiie base associated with the acid in their ash combining
with carbonic acid to form carbonates, which act as above
described.
Bacterial Action upon Carbohydrates of Foods. ā The
bacteria that act chiefly upon the carbohydrates belong to
the fermentative type. The substances formed as a result
of this activity axe certain acids ā lactic, butyric, formic,
acetic, oxalic, and possibly alcohol. Certain forms of carbo-
hydrates are more susceptible to bacterial fermentation than
others. Herter claims that sucrose and glucose are much
more so than lactose, maltose, or starch. The substances
thus formed through bacterial activity are not believed to
be toxic in character, but merely irritating. However, the
irritation arising from excessive fermentation in the stomach
may lead to gastric disturbances of a more or less serious
nature; hence the amount of carbohydrate taken under cer-
tain conditions must be adjusted carefully.
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14 DIETETICS FOR NURSES
The Effect of Heat upon Carbohydrates. ā The
changes wrought in the carbohydrates as a result of heat
have already been discussed to a certain extent. It is seen
that the sucrose (cane sugar) is soluble alike in hot and
cold water; the same is true of maltose; but lactose is much
more soluble in hot water than it is in water which has not
been heated. So far as their digestibility is concerned, the
application of heat (boiling) neither increases nor decreases
the utilization of these sugars by the body.
With starch it is an entirely different matter. It has
been found that the application of heat, either as dry heat,
or in the presence of moisture, brings about a definite change
in the character of the foodstuff. Pure starch admixed with
water and boiled, passes into a condition of colloidal dis-
persion, or semi-solution, known as starch paste (Sherman).
This is graphically illustrated in the cooking of potatoes,
in which the starch and water are mixed in nature ; and in
the cooking of cereals and like starchy foods, to which water
is added in preparation for their cooking. In both cases
the application of heat adds greatly to the digestibility of
the raw material by reason of the change which is wrought
in these substances, causing them to be more readily acted
upon by enzymes in the digestive juices.
This solubility of carbohydrates in hot water may be
utilized in the washing of utensils in which these substances
have been prepared; thus saving much time and effort on
the part of the nurse in either the diet kitchen or in the
home.
FATS
The second member of the organic food group, and one
which is almost as widely distributed throughout animal
and vegetable life as the carbohydrates, is found in the fats.
This foodstuff, while composed of the same chemical ele-
ments that go to make up the carbohydrates, contains these
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FOOD 15
elements in different proportions; that is, fats contain less
oxygen and more hydrogen than carbohydrates.
Typical Fats. ā The fata (as already shown in the
Table on page 5) are derived from both animal and plant
life, but, like the carbohydrates, do not always occur in the
same form. Those of animal origin include:
Adipose Tissue of man and animals, tallow of mutton,
suet, and oleo oil of beef, lard or pork.
Phosphorized Fats, which include lecithin and lecithans,
occur abundantly in the brain and nerve tissues and to a
less extent in the cells and tissues of man, animals, and
plants of which it seems an essential part. Egg yolk is the
most abundant source of phosphorized fat in food material,
but milk likewise furnishes an appreciable amount.
Cholesterol (fat-like substances). ā "The fatty secre-
tions of the sebaceous glands of man and of the hi^er ani-
mals which furnish the natural oil for hair, wool and
feathers," (Starling), lanoline, which is a purified wool fat,
consist chiefly of cholesterol. According to Mathews,
cholesterol is an essential constituent of the blood, and is
found in the brain and in nearly all living tissues. It is
likewise believed to be the "mother substance" from which
bile acids are derived.
Fat Soluble "A." ā The vitamine factor which occurs
dissolved in certain fats, namely, milk (whole), butter, egg
yolk, the organs of animals, and cod-fish liver.
Definition of Fat. ā The fats are all glycerides; that is,
they are substances made up of combinations of fatty acids
and glycerine, which constitute a definite group of chemical
compounds, certain members of which are liquid in form,
while others are solid, or semi-solid. The liquid fats are
known as fatty oils. The fatty acids in which we are chiefly
concerned in this study are: Butyric, Stearic, Oleic, and
Palmitic. Most of the common fats owe their form and
flavor to the type and amount of the various fatty acids of
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16 DIETETICS FOR NURSES
which they are composed. For example, butter is made up
of ten fatty acids; but its soft, solid form is due to the olein
and palmitin (glycerides of oleic and palmitic acids) which
it contains; and its characteristic flavor, as well as its name,
to its butyric acid content (about 5 to 6%). It is evident
that the degree of softness or hardness of a fat may be de-
termined chiefly by the amount of oleic acid in its composi-
tion. Most of the common oils with which we are familiar
in food are composed chiefly of olein. Stearin (the glyceride
of stearic acid) is the hardest of the fatty acids, while pal-
mitin, although classed with the solid fats, is not so hard
as stearin. Lard and butter are higher m olein and pal-
mitin and are consequently semi-solid, while suet and tal-
low, consisting chiefly of stearin, are much harder than the
other food fats.
Characteristics of Fats. ā The fats are all insoluble in
water, and only partially so in cold alcohol, but they dis-
solve readily in ether. As a rule, the fat occurring in the
animal body is more or less characteristic of the species.
For example, animals that live on land have a harder fat
than those living in the water; warm blooded animals,
harder fats than cold blooded ones (fish) ; and carnivorous
animals, harder fats than herbivorous species.
Fats are lighter than water, hence will float in it. An
emulsion is a suspension of fat in a fluid, and the fat in
this case must be very finely divided and mixed with some
other material which will prevent a coalescence of the fat
globules. In milk, which is one of the best natural emul-
sions, the additional substance is protein.
Effect of Heat upon Fat. ā When fats rre brought to
a high temperature, the glycerine which they contain de-
composes with the production of a substance known as
acrolein, which has an irritating effect upon the mucous
membranes. It is possible that the over-heated fatty acids
add their quota to the production of irritating fumes. As
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FOOD 17
a rule, it is inadvisable to use frying as a method of pre-
paring food for the sick or for children. Doubtless, if every
cook understood the exact degree of heat to apply in frying,
and knew just how moist to have the food mixture which
she intended to cook in this manner, better results would
be obtained ; but since the average cook knows little about
the scientific application of heat to fat or the changes
brought about thereby, it is safer to make use of other
methods of food preparation under the circumstances.
Functions of Fat. ā This foodstuff undoubtedly serves
as the most compact form of fuel available to the body for
the production of energy. Weight for weight, fat furnishes
twice as much heat as the carbohydrates, and in bulk the
difference is even more striking; for example (about) two
tablespoonfuls of sugar are required to produce 100 calories,
whereas one scant tablespoonful of olive oil will produce a
like number of heat units. As a source of supply for re-
serve energy in the body, fat is most valuable. This reserve
fuel is stored in the form of adipose tissues underlying the
skin and surrounding the vital organs, lending contour to
the form and protecting the organs from jars and shocks.
Distributed throughout the body, fat may be found as (a)
cholesterol (in the cells of the muscles, organs, and nerve
tissues), which acts as a protection against the destruction
of the red blood cells; (6) phosphorized fat (lecithin), the
universal distribution of which, according to Starling, seems
to indicate that it plays an important part in the metabolic
process of the cells, serving as a source of phosphorus which
is required for the building up of the complex nucleo-
proteins of the cell nuclei.
PROTEINS
Upon investigation it was found that neither the fats
nor carbohydrates were the chief constituents of the active
tissues. It was found, in fact, that the carbohydrates oc-
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18 DIETETICS FOR NURSES
curred in very small quantities only in the muscles, and
that frequently the quantity of fat was likewise limited.
Other substances, containing nitrogen and sulphur in addi-
tion to carbon, oxygen, and hydrogen, which were invari-
ably present, and which are essential constituents of all
tissues and cells, both in animals and in plants, must be
necessary to all known life. To these substances, believed
at the time to be the fundamental constituents of all tis-
sues, Mulder gave the name Protein, from the Greek, mean-
ing "to take first place." Later investigations proved that,
while the proteins were essential to the building and re-
pairing of the tissues and cells in general, they were not
the only factors concerned in the work ; that certain mineral
salts were necessary constituents of all tissues, and must
be present in order for any normal growth and development
to occur.*
Composition of Proteins. ā The average nitrogen con-
tent of common proteins is about 16%; that is, in 100
grams of protein there will be approximately 16 grams of
nitrogen, or in 6.25 grams of protein there will be 1 gram
of nitrogen. To estimate the protein content of a food
when the percentage of nitrogen is known, it is necessary
simply to multiply the percentage of nitrogen present, by
the nitrogen factor, 6.25; or, if the amount of nitrogen is
desired, when the percentage of protein is given, to divide
by same factor.
Construction of Proteins. ā In plant structure the
building up of the proteins is accomplished by the plants
from inorganic substances existing in the soil and air; but
in the animal body this is not possible, because the con-
struction of the tissues requires the use of other proteins ā
the most available ones being found in food. Each animal
* Scientists are proving the need for certain vitamine factors in the diet
in order that the growth and development of young tissues and the repair
of adult tissues may proceed. The part played by these substances will
be discussed later.
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FOOD 19
(or species) forms the proteins characteristic of its own
tissues^ ā while the proteins of food are similar to those
found in the body, they cannot be utilized in their original
form, but must be split into simpler substances from which
the cells of the various tissues throughout the body may
select those particularly adapted for their purpose. These
transformed substances are known as amino acids, the pro-
duction of which is a result of digestion in the digestive
tract. There are about seventeen of these acids entering
into the construction of the common proteins. One scientist
has likened these units to letters of the alphabet, which,
being combined, spell many proteins. When a protein con-
tains all of the essential units, it may be said to be "com-
plete," the best example of which may be seen in milk, eggs,
and meat. When a protein lacks some of the essential
elements, or letters of the protein alphabet, it is said to be
incomplete. Gelatin is the best example of this type of
protein, but the cereals and beans must likewise be supple-
mented by other substances; milk being the one most
generally used for this purpose. For the purpose of building
young tissues, and maintaining those already mature, it is
logical to use foods containing the foodstuffs in their best
form; that is, those that not only contain the complete
protein, but also the requisite mineral salts and vitamines.
Foods lacking in some of these respects become adequate
when supplemented by these foods which can supply the
missing constituents; hence, the use of such incomplete
protein foods need not necessarily be abandoned, for, as in
the case of cereals, the foods are both economical and pal-
atable, and, when used in addition to milk, furnish valuable
adjuncts to the dietary.
Classification of Proteins. ā A brief description of some
of the more important proteins with which we are chiefly
concerned will serve to simplify the formulation of a diet.
Those assuming the most important position in nutrition
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20 DIETETICS FOR NURSES
and food are globulins, albumens, nucleoproteins, phos-
phoproteins, hemoglobins, and derived proteins such as
proteoses and peptones. The albumens and globulins as-
sociated together occur in the tissues of both animals and
plants. The albumens are richer in sulphur than the
globulins and are found more abundantly in the animal
fluids, such as the blood, while the globulins predominate
in the more solid tissues of animals and in plants. The
close association of these two proteins is particularly notice-
able in the blood and cells. They have different character-
istics, however.
Albtunins. ā The best examples are found in egg albu-
min (white of egg), lactalbumin (milk), serum albumin
(blood), leucosin (wheat), legumelin (peas). Albumins are
all soluble in pure water, and are coagulable by heat. Coag-
ulation, due to the action of the ferments in the body,
takes place in milk,- blood, and muscle plasma. Certain
albumens are particularly adapted for the building and re-
pairing of tissues. Among those that have been used in
feeding experiments to determine whether or not they were
capable, when used as the sole protein in the diet, of main-
taining animals in normal nutrition, and of supporting nor-
mal growth in the young animal, ā may be cited lactalbu-
min and egg albumin. These experiments provided diets
adequate in other respects, the object being to determine
the value of the various proteins. It was found that the
albumin from milk was more efficient in this respect than
the egg albumin.*^
In the invalid dietary the solubility of the albumins in
water makes them of especial value as reinforcing agents,
since they may be introduced into fluids without materially
altering either their flavor or their bulk.
Globulins. ā Simple proteins, insoluble in pure water,
ā¢"Chemistry of Food and Nutrition" (2d ed.), by Sherman.
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FOOD 21
but soluble in neutral salt solutions; examples^ muscle
globulin, serum globulin (blood), edestin (wheat), physelin
(beans), legumin (beans and peas), tuberin (potatoes),
amandin (almonds), arachin, and conarachin (peanuts).
Alcohol-Soluble Proteins. ā Simple proteins soluble in
alcohol of from 70-80% strength. Insoluble in absolute
alcohol, water and other neutral solvents. Examples of
these proteins may be seen in the ^iadin of wheat, zein, of
corn, and hordein of barley.
Albuminoids. ā These substances represent one group
of incomplete proteins, inasmuch as they cannot alone sup-
port protein metabolism. However, they are classed with
the proteins and may be substituted for at least a part of
these compounds in the daily dietary, since they are able
to do much of the work of the pure proteins. The best
example of this group is seen in gelatin. This sub-
stance contains many of the structural units of meat protein
but in very different relative amounts. It has not, there-
fore, the chemical units necessary to repair the worn-out
parts of cell machinery.*
Conjugated Proteins: ā Nucleoproteins, Phosphopro-
teins and Hemoglobin, (a) Nucleoproteins. ā This type
of protein is characteristic of all cell nuclei, and is particu-
larly abundant in the highly nucleated secreting cells of the
glandular organs, such as the liver, pancreas, and the thy-
mus gland. The nucleoproteins are composed of simple pro-