body in which it traverses more than thirty feet of the intestinal
tube before that part of it which the body cannot use is ejected; the
process of metabolism begins the moment the lips touch it. The six
salivary glands which are located in the mouth manufacture saliva,
which flows out through numerous openings, and mixes with food as it
is chewed. The saliva not only moistens the food, thus allowing it to
be more easily swallowed, but it also has a most important chemical
office, converting all starchy food matter into sugar, and thus
performing the first and one of the most essential steps in the process
of digestion.
After the food has been masticated and saturated with saliva, it passes
down the throat through the gullet, which performs a peculiar muscular
contraction, thrusting downward the particles of food. The conversion
of the starch in food into sugar, or glucose, which is begun by the
saliva in the mouth, is continued as the food passes into and down the
gullet, but stops almost completely when the food once reaches the
stomach.
THE WORK OF THE STOMACH
It is in the stomach, on the other hand, that most of the work of
digesting the albuminoids, or proteids, of food is performed by the
gastric juice. The stomach is a pear-shaped bag, that holds about three
pints of material, or three-quarters of an ounce for every inch of the
individual’s height. Food enters it through the gullet on the upper
left hand side, just below the heart. Myriads of glands in the walls of
the stomach are active in the formation of either pepsin, or an acid
fluid which, when combined with pepsin, forms the gastric juice.
At the back of the stomach, partly overlapping it, lies the liver,
which discharges a liquid called the bile into the alimentary canal
just below the stomach. Behind the stomach, lies a large gland called
the pancreas, which discharges a remarkable fluid, named pancreatic
juice, into the intestine through the same opening which the liver uses
for its bile. Connected with the stomach is the small intestine, which
is the narrow portion of the alimentary canal, and the largest and most
important of all the digestive organs. It is some twenty-five feet in
length, and its walls are everywhere covered with glands which secrete
and exude mucous and other fluids.
At the lower end of the intestine is the colon or large intestine which
is not a digestive organ in itself, but is a reservoir in which the
food is stored up for a short time, to allow opportunity for complete
absorption of the digested portions.
THE ELEMENTS OF FOOD
Although there may be thousands of different dishes, and combinations
of foodstuffs, fundamentally they are all closely akin, and can be all
resolved into a few quite simple elements: Proteid, Carbohydrate, Fat
or Mineral Salts, or combinations of these; the Proteid class having
many subdivisions, and the Carbohydrates being made up of the various
sugars and starches.
We also know definitely just what use the body makes of these various
substances. The Proteid is the up-builder of tissue, the essential
foodstuff without which life cannot exist. If we compare the human body
to an engine, as nearly all physiologists seem bound to do, we may say
that Proteid is like the brass, or other metal, of which the structure
is composed. The various Carbohydrates and the Fats are the fuels from
which are derived the energy which animates and operates the mechanism.
The Mineral Salts are used to supply various important bodily needs,
such as elements required by the bones, or the delicate tissue in the
eyes, the enamel for the teeth, and so forth.
THE WORK OF THE DIGESTIVE JUICES
As there are five main food elements, namely, proteid, starch, sugars,
fats, and salts, so also there are five main digestive fluids, the
saliva, the gastric juice, the bile, the pancreatic juice, and the
intestinal juice.
The saliva is an alkaline fluid that digests starch. Its work is
checked by the presence of acid substances; which explains why the
digestive action of saliva ceases soon after it enters the stomach.
Hence the importance of giving the saliva ample opportunity to perform
its function, by complete mastication, is obvious.
The gastric juice, of which about seventy ounces is formed by the
stomach daily, contains in addition to hydrochloric acid, a quantity
of pepsin, which with the acid dissolves all sorts of proteids or
albuminous substances, like meat and eggs; and it also contains rennet,
which coagulates milk. The gastric juice digests proteids by converting
them into pepsin, an exceedingly soluble substance which passes readily
into the blood.
The bile manufactured by the liver has the function of digesting fats.
Fats are not changed chemically, as are starches and proteids. They are
only broken up into particles so small that the cells of the mucous
membrane can take them up and effect their removal into the blood
stream.
The pancreatic juice is able to perform the work of all the three
digestive fluids which we have already named. In fact, it is even more
powerful than saliva in the digestion of starch, since it is able to
digest raw as well as cooked starch, which the saliva cannot do. It is
also able to convert proteid into peptone, as does the gastric juice;
and it emulsifies fats, as does the bile.
The intestinal juice digests cane sugar, and is supposed to have a
digestive influence upon all the other food elements.
The mineral salts which are taken into the body are dissolved by all
the digestive fluids which we have named, some by the saliva and the
juices of the intestinal tube, and others, which require acids for
their solution, by the gastric juice.
Nearly all these digestive fluids are also powerful antiseptics and are
able to destroy germs when the health of the body as a whole is good.
The gastric juice, for instance, acts as an antiseptic, preserving the
stomach contents from putrefaction during the digestive process. It is
a remarkable fact that the gastric juice, although it is so essential
to life, is a deadly poison, which, when introduced into the blood
produces insensibility and death.
These digestive juices and organs are able completely to dispose of
all the food elements which are introduced into the body, save proteid
alone. The sugars and starches are either completely absorbed and
oxidized, or stored up in the form of surplus fat. The oxidation or
burning up of proteid, however, is never complete. There is always a
certain amount of unburnable substance left behind from the processes
of metabolism, which the liver and kidneys of the body have to dispose
of. If only as much proteid as is needed by the body for the upbuilding
of its tissue, and the repair of waste, is taken, the body can very
readily handle it; but an excess of proteid is highly disadvantageous.
Professor Chittenden, in his great work, “The Nutrition of Man,” has
set forth in elaborate detail the process of the assimilation of
proteid. It appears that there are many kinds of proteid; the proteid
of eggs is different from that of meat, and that again from the
proteid of beans, and so on; and human proteid is different from all.
Consequently, the body is obliged to transform every kind of proteid
which is brought to it. This proteid is then absorbed by the blood, and
carried to the tissues, which are kept perpetually bathed in a supply
of nutritive material. The taking of more proteid than is needed would
not be so dangerous if it were simply passed on without being digested;
nor even if it were digested and transformed, and then promptly
eliminated. But what actually happens is that the new proteid taken in
is passed through all the stages of assimilation, and drives out in
front of it, so to speak, the proteid which has already been prepared,
but has not yet been used. And the result is, of course, to throw a
double strain upon the liver and the kidneys, the organs of elimination.
Professor Chittenden also points out the common blunder which is made
in assuming that persons who are doing hard work need an additional
amount of proteid substance. One commonly hears the phrase that
laborers and athletes can eat meat in large quantities, and “work it
off.” As we have seen, one can “work off” sugars and starches and fats
completely; but one cannot “work off” proteid completely. Professor
Chittenden is now recognized as the leading authority of the world upon
this particular question; and he sets forth clearly in his book the
fact that the quantity of proteid needed is not increased by muscular
activity. One may work as hard as he pleases, but his body will use
no more nitrogen, save only in the case where a sufficiency of other
food elements is not supplied. Only as a last resort will the system
undertake the labor of burning up proteid to make energy.
HOW MUCH SHOULD WE EAT
When foodstuffs are taken into the body, digested, assimilated, and
used up, they produce the same amount of heat and other forms of energy
as if burned outside of the body; and hence it follows that the number
of calories, or units of heat, represented in a given foodstuff, is
taken by scientists as a common measure of its food value.
A calory is a heat unit, which has been adopted as a means of
estimating the nutritive value of foodstuffs. It represents the amount
of energy required to raise the temperature of four pounds of water one
degree Fahrenheit. The number of calories contained in food is obtained
by burning the food and measuring the heat produced by means of a
calorimeter.
It has been calculated that the normal, average person needs from one
hundred and sixty to two hundred and forty calories of proteids every
day, in order to build blood and tissues. He needs daily from five
hundred to nine hundred calories of fats, which supply heat.
He needs of carbohydrates, which are the starches and sugars, and which
the body uses to produce energy for work and heat, from one thousand to
one thousand four hundred calories daily. It is declared by Chittenden
and Kellogg, whose work has overset the old notions, that the total
number of calories, or food units, should rarely exceed two thousand.
Two thousand calories are furnished respectively by twenty-eight
ounces of bread, or ninety-six ounces of milk, or sixty-two ounces of
potatoes, or nine ounces of butter. One quarter of each of these, or
any other fractions which together equal unity, will make up a ration
containing two thousand calories.
It is quite impossible, however, to make a hard and fast rule in this
matter. Every individual differs from others in his requirements.
Moreover, the weather, the season of the year, the amount and kind
of work done, are all factors in the situation. Hard physical work
and exposure to cold demands the largest food supply. A person who
naturally perspires freely needs more food than a person who does
not, because of the large amount of heat carried off from his body by
the evaporation of sweat from the skin. Adults require food chiefly
to repair waste and losses. Growing children require in addition
to food to repair waste and losses, material for tissue building.
According to the best authorities upon the diet of children, a
growing infant utilizes fully one-third of its total intake of food
in tissue building. When an adult becomes emaciated he requires more
tissue building material than the normal adult, his need for it being
practically the same as that of a growing child.
We give below a table showing the average number of food units or
calories required daily by people of various heights and weights. This
table is one drawn up by Dr. J. H. Kellogg, Superintendent of the
Battle Creek Sanitarium. In calculating the number of calories required
in a given case, the estimate should be based not upon the actual
weight of the individual, but upon the weight of the average person of
his height.
“Persons who are in good health,” says Dr. Kellogg, “and find their
weight somewhat greater than the figures given in the table, should
not necessarily consider themselves obese. While above the average in
weight, their condition is probably natural, and no attempt should be
made to reduce the weight to any considerable amount, as injury may
result. The average for adults applies especially to healthy adults
between twenty and thirty years of age. Most people who are above
forty years of age have a natural tendency to increase of flesh, which
requires no attention unless it becomes excessive. Any reduction in
foods made by an obese person should be in carbohydrates rather than
in proteids or fats, unless these latter have been taken in excess.”
TABLE NO. 1
Showing for different ages the average height, weight, and the number
of food units or calories required daily.
_Boys_
Height in Weight in Calories or
Age Inches Pounds Food Units
5 41.57 41.09 816.2
7 45.74 49.07 912.4
9 49.69 59.23 1,043.7
11 53.33 70.18 1,178.2
13 57.21 84.85 1,352.6
_Girls_
Height in Weight in Calories or
Age Inches Pounds Food Units
5 41.29 39.66 784.5
7 45.52 47.46 881.7
9 49.37 57.07 1,018.5
11 53.42 68.84 1,148.5
_Men_
Calories or Food Units
Height in Weight in
Inches Pounds Proteids Fats Carbohydrates Total
62 110.0 165 495 890 1650
64 121.0 181 543 1086 1810
66 132.0 198 594 1188 1980
68 143.0 215 645 1290 2150
70 154.0 231 693 1386 2310
72 165.0 247 741 1482 2470
74 176.0 264 792 1584 2640
_Women_
Calories or Food Units
Height in Weight in
Inches Pounds Proteids Fats Carbohydrates Total
57 78.4 118 344 688 1180
59 88.8 132 396 792 1320
61 99.2 149 447 894 1490
63 109.3 163 489 978 1630
65 120.2 180 540 1080 1800
67 130.7 195 585 1170 1950
69 143.0 215 645 1290 2150
71 155.0 232 696 1392 2320
PRACTICAL APPLICATION OF DIETARY RULES
While dieticians have ascertained the number of food units daily
required by the average person, yet on no point do they reach more
thorough agreement than in saying that the average person should not
establish any hard and fast rules as to the quantity and kinds of food
he consumes. It is really only an invalid, one who is in a physician’s
care, who needs to have his food regulated in this precise fashion. The
average person should be careful to practice thorough mastication, and
should see to it that the proteid part of his meals is not excessive,
but he should avoid worrying about his food habits. Any person who
fusses and fumes about the kind of foodstuffs and the number of
calories they contain, will be apt to cause himself harm; for science
has proved by laboratory experiments, which we shall describe later
on, that worry, in fact any of the unpleasant emotions, exercises a
prohibitive effect upon the flow of digestive juices.
The really important thing to do is to follow a simple dietary,
which at the same time is well balanced in its food elements, well
cooked, and tastefully served. The housewife will see to it that the
foodstuffs she chooses represent more of carbohydrates and fats than of
proteids; her guiding rule in this matter being that _the proportion
of proteids to the other food elements be ten per cent._ The United
States Department of Agriculture has prepared a list of foodstuffs,
comprising all those in common use, which shows the proportion of their
constituents, and their total energy value, in calories, per pound of
material.
This is “Bulletin No. 28, Revised Edition,” the work of two of the
leading physiological chemists of America, W. O. Atwater and A. P.
Bryant; and may be had on sending five cents to the Department. We have
inserted in the Appendix a selected list of foodstuffs taken from this
publication; and we give here a rough classification of foods, from
which one can see at a glance their leading elements:
FOODSTUFFS WHICH ARE RICH IN PROTEIDS
Eggs
White of Egg
Skimmed Milk
Buttermilk
Yogurt
Cottage Cheese
Nut Products
FOODSTUFFS WHICH ARE RICH IN FATS
Butter
Nut Oils
Olive Oil
Cream
Olives
Nuts (except chestnuts)
Egg Yolks
FOODSTUFFS WHICH ARE RICH IN CARBOHYDRATES
Potato
Rice
Breads
Cereal Preparations
PURE CARBOHYDRATES
Fruits (raw and cooked)
Fruit Juices
Fruit Jellies
Honey
Malt Honey
Marmalades
FOODSTUFFS WHICH ARE RICH IN PROTEIDS AND FATS
Nuts
Nut Butters
Eggs
Cheese
Nut Products
FOODSTUFFS WHICH ARE RICH IN PROTEIDS AND CARBOHYDRATES
Peas
Beans
Lentils
Chestnuts
Skimmed Milk
Gluten Preparations.
FOODSTUFFS WHICH CONTAIN ALL THE FOOD ELEMENTS IN FAIRLY GOOD PROPORTION
Crackers
Batter Breads
Pastry
Malted Nuts
Custards
Puddings
Salads
Sandwiches
Soups (other than meat or fish soups).
V
HOW FOODS POISON THE BODY
In our survey of the processes and organs of digestion, we saw that
after food has traversed the stomach and small intestine it passes into
the colon, where it must remain for some considerable time, while the
absorption of its digested elements is completed. And this brings us to
the most important of the discoveries of the new hygiene. It has been
found that some of the foods which human beings eat are loaded with
injurious bacteria, and with the poisons which these bacteria produce.
And others of them are indigestible, and when they reach the colon,
become a source of incubation for countless billions of other bacteria.
It was demonstrated by Metchnikoff that these poisons are absorbed into
the system, and are the cause of manifold evils. This is the process
which is called “autointoxication.”
It would not be regarded as an exaggeration by the leading
physiologists of the world to-day to speak of autointoxication as the
primary source of nine-tenths of the afflictions from which humanity
suffers. Any one would be prepared to admit that the banquet he had
attended on the previous night was responsible for the headache
which he has on the present morning; but the investigations of
bacteriologists have revealed that the food habits of which banquets
are typical are responsible for a chronic ailment, of which such
diseases as gout, rheumatism, Bright’s disease, consumption, and
pneumonia are merely symptoms.
THE INVESTIGATIONS OF METCHNIKOFF
Elie Metchnikoff, sub-director of the Pasteur Institute of Paris, is
a philosopher, as well as a physiologist; a philosopher who brings to
the support of his speculations the exact methods of the laboratory.
He, with the other great leaders of the new art of health, is at last
removing from science the reproach leveled at it by Metchnikoff’s great
fellow-country-man and friend, Tolstoi, who said that science was
useless to man, since it did not direct its attention to the problems
which mean most to humanity, such as the great questions of life and
death, but confined its efforts to investigating useless birds and
butterflies.
[Illustration: M. ELIE METCHNIKOFF, OF THE PASTEUR INSTITUTE OF
PARIS.
His researches have thrown great light on autointoxication. He
believes that the normal life should be over 125 years long.]
The books in which Metchnikoff has recorded the results of the
investigations which for many years he has been making into the
problems of old age and death, have caused a profound sensation in the
scientific world. In these books, the great Russian emphatically and
definitely ranks himself with the optimists. He states that scientific
study of the constitution of man, and of the workings of man’s nature,
and of his environment in the world, do not support the view that
man is born unto sorrow as the sparks fly upward—to quote the words
of the Psalmist—but can really be fitted to live a useful and happy
life, ending in a calm and peaceful old age—if man will but turn his
attention to the knowledge by which he can really live in harmony with
his environment. Metchnikoff has arrived at the conclusions that man
and woman would live to be at least one hundred years old, if they
could enable their bodies to eliminate those deadly toxins which are
the product of the activities of the bacteria which inhabit the human
body, as well as of the body’s own organic processes.
Age is not always to be computed in years. As a common saying puts the
case, “A man is as old as he feels, a woman as old as she looks.” A
famous French physiologist has altered this to read, “A man is as old
as his arteries.” The primary change produced by the coming of old age
is the hardening and withering of the arteries. As the result of this
withering process, a large number of the smaller arteries disappear, so
that the blood supply of the muscles, brain, heart, and other important
organs, is cut off. This is the change that is technically known as
“arterio-sclerosis.” It is quite often found in persons of less than
fifty years of age. On the other hand, Harvey, the famous discoverer
of the circulation of the blood, declared that in the post-mortem
examination made of Old Parr, the celebrated Englishman who died at the
age of one hundred and fifty-two years and nine months, he found not a
trace of this degenerative change.
In the United States the average length of life is about forty-two
years; but a large and growing school of modern scientists (comparative
anatomists) declare that the natural age of the human family cannot
be much less than from one hundred, to one hundred and twenty-five
years. Any death that comes at least before one hundred years, is not
a natural death but accidental or violent. From the point of view of
science, death through disease is just as accidental and violent as
the extinguishment of life in a railway wreck or by drowning in the
sea; and the fact that the average life of man is to-day only about
one-third of that which nature designed for him is due to the operation
of autointoxication more than to any other cause.
Natural death in man is therefore more a possibility than an actual
occurrence. Nevertheless, instances have been recorded of the actual
appearance of the instinct in aged people, where the wished-for
death came not because life was burdensome, not because of poverty,
disease, or loneliness, but seemed to arrive as naturally as sleep to
a younger person, or the wish for more extended life which all of us
possess. Metchnikoff states that instances of veritable cases showing
an instinct of death are extremely rare, yet this instinct really
does seem to lie deep in the constitution of man. And if the cycle of
human life followed an ideal course, he concluded men and women after
living a healthy and useful life extending over at least a century,
with their usefulness and satisfaction in life at maximum during the
latter portion of that period, would then give themselves up calmly and
gracefully to the arms of death, as to the arms of a friend laying them
down to earned and wished-for rest. Old age would have no terrors, and
death no victory.
It has been, perhaps, Metchnikoff’s crowning discovery, that the
immediate cause of old age is not merely the accumulation of poisonous
wastes, but is due to a destruction of the tiny cells which make
up the tissues by certain cells of the body, which he describes as
macrophages. These are of an especial kind, which wander through the
body and devote their energies to the destruction of waste particles
and organic débris—particles of material which are not used in the
building up of tissue, just as particles of brick and wood might be
left on the ground after the erection of a house. These macrophages
enact the part of scavengers, very much like the turkey buzzards, which
in southern cities eat up the refuse from the back alleys. Just so
long as these wandering cells confine themselves to this useful and
necessary work, all goes well; but when the vigor of the body cells has
been lowered by the accumulation of tissue poisons, these scavenger
cells turn traitor to the cause of the body and attack the very cells
which they formerly guarded. They have been photographed in the very
act of devouring nerve cells in the brains of old people.
HOW TO PREVENT DEGENERATION OF TISSUE
It can readily be seen that if the pernicious activity of these
macrophages can be prevented, the coming on of degenerative changes in
the body tissue will be much delayed. The practical question, which
Metchnikoff therefore asked himself was, How may this revolt of the
macrophages, this rebellion of the body’s army, be prevented?