+---------------+-----------------------------------------------------+
| |Moleschott. |
| | |Ranke.[1] |
| | | |Forster. |
| | | | |Hultgren[2] and Landergren. |
| | | | | |Atwater. |
| | | | | | |Studemund.[3] |
| | | | | | | |Schmidt.[4]|
| +------+------+------+------+------+------+------+----+
| |grams |grams |grams |grams |grams |grams |grams | |
+---------------+------+------+------+------+------+------+------+----+
|Proteid | 130 | 100 | 131 | 134 | 125 | 114 | 105 | |
|Carbohydrates | 550 | 240 | 494 | 523 | 400 | 551 | 541 | |
|Fats | 40 | 100 | 68 | 79 | 125 | 54 | 63 | |
|Fuel value | | | | | | | | |
| (calories)[5] | 3160 | 2324 | 3195 | 3436 | 3315 | 3229 | 3235 | |
+---------------+------+------+------+------+------+------+------+----+
In many of these diets it is to be noted that the proteid requirement is
placed at even a higher figure than Voit’s standard. Similarly, Erisman,
studying the diets of Russian workmen having a free choice of food and
doing moderately hard work, found the daily diet to be composed of 131.8
grams of proteid, 79.7 grams of fat, and 583.8 grams of carbohydrate,
with a total fuel value of 3675 large calories. Further, Hultgren and
Landergren[6] found that Swedish laborers doing hard work had as their
daily diet 189 grams of proteid, 110 grams of fat, and 714 grams of
carbohydrate, with a total fuel value of 4726 large calories. Voit
found that German soldiers on active service consumed daily 145 grams
of proteid, 100 grams of fat, and 500 grams of carbohydrate, with a
total fuel value of 3574 large calories. Lichtenfelt,[7] studying the
nutrition of Italians, states that an Italian laborer doing a moderate
amount of work requires 110.5 grams of proteid and a total fuel value for
the daily food of 2698 calories, while at hard labor he needs 146 grams
of proteid daily, with carbohydrates and fat sufficient to give 3088
large calories. In our own country Atwater,[8] who has made many valuable
observations upon the dietetic habits of different classes of people
and under different conditions of life, has stated that a somewhat more
liberal allowance of proteid would seem desirable, say 125 grams, with a
total fuel value of 3500 large calories for a man doing severe muscular
labor.
In what is perhaps the latest book on alimentation, Armand Gautier,[9]
writing of the French people, states that the ordinary man in that
climate needs daily 110 grams of albuminous food, 68 grams of fat,
and about 423 grams of amylaceous or saccharine food. It is possible,
however, says Gautier, that the quantity of albuminous food can be
reduced, if necessary, to 78 grams per day in case a man is not doing
work and takes in addition at least 50 grams of fat and 485 grams of
carbohydrate food. Where, however, an individual works eight to ten hours
a day, the ration, says Gautier, must be increased to at least 135 grams
of albuminous food, with 85 to 100 grams of fat, and with from 500 to 900
grams of starchy food.
While these figures may be taken as showing quite conclusively the
dietetic standards adopted by mankind, there is no evidence whatever
that they represent the real needs or requirements of the body. We may
even question whether simple observation of the kinds and amounts of
food consumed by different classes of people under different conditions
of life have any very important bearing upon this question. They throw
light upon dietetic habits, it is true, but such observations give no
information as to how far the diets in question serve the real needs of
the body. We may find, for example, that under certain given conditions
of diet the people in question have the appearance of being well
nourished, and that they do their work with apparent ease and comfort;
but might not these same results follow with smaller amounts of food? If
so, there must of necessity be a certain amount of physiological economy
under the more restricted diet, and a consequent ultimate gain to the
body through diminished wear and tear of the bodily machinery.
Indeed, experimental work and observations scattered through the last
few years have suggested the possibility of much lower standards of
diet sufficing to meet the real physiological needs of the body. Thus,
Hirschfeld,[10] in 1887, found in experimenting on himself (24 years of
age and weighing 73 kilos) that it was possible to maintain nitrogen
equilibrium on a diet containing only 5 to 7.5 grams of nitrogen per
day, or 35 to 45 grams of proteid, for a period of ten to fifteen days.
The amount of non-nitrogenous food consumed, however, was fairly large,
especially the amount of butter,—frequently 100 grams a day—the average
fuel value ranging from 3750 to 3916 large calories daily. In 1888
Hirschfeld,[11] again experimenting on himself, maintained nitrogen
equilibrium for several days on 7.5 grams of nitrogen per day, with
fats and carbohydrate sufficient to yield a total fuel value of 3462
large calories as the daily average. The chief criticism of Hirschfeld’s
experiments is that he failed to obtain in all cases definite analytical
data of the food-stuffs employed and failed to determine the nitrogen of
the fæces. Still his results are of value as indicating the possibility
of maintaining nitrogenous equilibrium for a brief time at least on a low
proteid intake.
Kumagawa,[12] studying especially the diet of the Japanese and
experimenting on himself (27 years old and weighing 48 kilos), found
with a purely vegetable diet, containing per day 54.7 grams of proteid,
2.5 grams of fat, and 569.8 grams of carbohydrate, that he showed for a
period of nine days a plus balance of nitrogen, indicating that his body
was laying on about 4 grams of proteid per day. The nitrogen excreted per
urine and fæces amounted to 8.09 grams per day, while the nitrogen in the
daily food amounted to 8.75 grams. It is interesting to observe in these
experiments, as indicating the degree of absorption of the vegetable food
(composed in large measure of rice) that the daily average of nitrogen in
the urine amounted to 6.069 grams and in the fæces 2.029 grams. In other
words, of the 54.7 grams of nitrogen-containing food only 37.8 grams
were absorbed, 12.69 grams passing out with the fæces. The total fuel
value of the absorbed food per day was 2478 large calories. Similarly,
Hirschfeld[13] has called attention to the fact that with many vegetable
foods especially, not more than 75 per cent of the ingested proteid can
be digested and absorbed, thus emphasizing the necessity of paying heed
to the _character_ of the proteid food in considering the nutritive value
of a given diet.
In some experiments reported by C. Voit[14] in 1889, on the diet of
vegetarians, E. Voit and Constantinidi found that nitrogenous equilibrium
was established in one man with about 8 grams of nitrogen, corresponding
to 48.5 grams of proteid as the daily diet, with large amounts of starchy
foods and some fat. Similarly, Nakahama[15] in the same year, studying
the diet (mostly vegetable) and nutritive condition of thirteen German
laborers in Leipzig, found that their daily food contained on an average
85 grams of proteid, but Carl Voit criticising these results states that
the men were of comparatively light body-weight—about 60 kilos—and not
well nourished.
Kellner and Mori,[16] studying the nutrition of a Japanese (weighing
52 kilos and 23 years of age) state that on a purely vegetable diet
containing 11.34 grams of nitrogen, of which only 8.58 grams were
digested, there was a distinct loss of body-weight, with a daily loss to
the body of 1.16 grams of nitrogen. On a mixed diet, however, containing
fish, it was possible to establish nitrogenous equilibrium with a daily
diet containing 17.48 grams of nitrogen, of which 15.27 grams were
digested and utilized. Similarly, Caspari,[17] 29 years old and weighing
66.2 kilos, found that while he could maintain his body in nitrogenous
equilibrium on 13.26 grams of nitrogen per day, he could not accomplish
it on 10.1 grams of nitrogen, though his daily food contained 3200 large
calories.
Other investigators, however, have found no great difficulty in
establishing nitrogenous equilibrium in man with much lower quantities
of proteid food. Thus, Klemperer[18] found in the case of two young men
of 64 and 65.5 kilos body-weight respectively, in an experiment lasting
eight days, that nitrogenous equilibrium was established on 4.38 and
3.58 grams of nitrogen per day, but with a daily diet containing in
addition to the small amount of proteid 264 grams of fat, 470.4 grams of
carbohydrate, and 172 grams of alcohol, with a total fuel value of 5020
large calories.
Peschel,[19] too, has reported experimental results showing that he was
able to establish nitrogenous equilibrium for a brief period with 7
grams of nitrogen daily, 5.31 grams appearing in the urine and 1.58 grams
in the fæces.
Caspari and Glaessner,[20] in a five-days’ experiment with two
vegetarians, found that the wife consumed daily, on an average, 5.33
grams of nitrogen, with fats and carbohydrates to equal 2715 calories,
while the man took in 7.82 grams of nitrogen and 4559 calories. Both
persons laid on nitrogen in spite of the low intake of proteid food.
Siven’s[21] experiments, however, are perhaps worthy of more careful
consideration. Of 60 kilos body-weight and 30½ years of age, his
experiments conducted on himself extended through thirty-two days with
establishment of nitrogenous equilibrium on 6.26 grams of nitrogen.
Moreover, in another experiment he was in nitrogen equilibrium for a day
or two at least on 4.5 grams of nitrogen. In Siven’s experiment, the most
noticeable feature is the added fact that the total intake of food per
day was comparatively low, with a fuel value of only 2444 large calories.
In this connection we may call attention to the recent experiments of
Landergren,[22] who found with four individuals fed on a daily diet
containing only 2.1 to 2.4 grams of nitrogen, but with a large amount
of carbohydrate, some fat and alcohol, that on the fourth day of this
“specific nitrogen hunger” only 3 to 4 grams of nitrogen were metabolized
and appeared in the urine. In other words, a healthy adult man having a
sufficient intake of non-nitrogenous food seemingly need not metabolize
more proteid than suffices to yield 3 to 4 grams of nitrogen per day.
Such data as these, of which many more might be quoted, surely warrant
the question, how far are we justified in assuming the necessity for
the rich proteid diet called for by the Voit standard? Voit, however,
with many other physiologists would apparently object to any diminution
of the daily 118 grams of proteid for the moderate worker, on the
ground that an abundance of proteid in the food is a necessity for
the maintenance of physical vigor and muscular activity. This view is
certainly reinforced by the customs and habits of mankind; but we may
well query whether our dietetic habits will bear criticism, and in the
light of modern scientific inquiry we may even express doubt as to
whether a rich proteid diet adds anything to our muscular energy or
bodily strength.
How far can our natural instinct be trusted in the choice of diet? We are
all creatures of habit, and our palates are pleasantly excited by the
rich animal foods with their high content of proteid, and we may well
question whether our dietetic habits are not based more upon the dictates
of our palates than upon scientific reasoning or true physiological
needs. There is a prevalent opinion that to be well nourished the body
must have a large excess of fat deposited throughout the tissues, and
that all bodily ills and weaknesses are to be met and combated by
increased intake of food. There is constant temptation to increase the
daily ration, and there is almost universal belief in the efficacy of
a rich and abundant diet to strengthen the body and to increase bodily
and mental vigor. Is there any justification for these beliefs? None,
apparently, other than that which comes from the customs of generations
of high living.
It is self-evident that the smallest amount of food that will serve to
keep the body in a state of high efficiency is physiologically the most
economical, and hence the best adapted for the needs of the organism. Any
excess over and above what is really needed is not only uneconomical,
but may be directly injurious. This is especially true of the proteid
or albuminous foods. It is, however, quite proper to question whether
a brief experiment of a few days in which nitrogenous equilibrium is
perhaps established at the low level of 4 to 5 grams of nitrogen, the
equivalent of 25 to 35 grams of proteid, is to be accepted as fixing the
daily requirements of the healthy man, offsetting the customs or habits
of a lifetime. Voit himself, however, has clearly emphasized the general
principle that the smallest amount of proteid, with non-nitrogenous food
added, that will suffice to keep the body in a state of continual vigor
is the ideal diet. Proteid decomposition products are a constant menace
to the well-being of the body; any quantity of proteid or albuminous
food beyond the real requirements of the body may prove distinctly
injurious. We see the evil effects of uric acid in gout, but there are
many other nitrogenous waste products of proteid katabolism, which with
excess of proteid food are liable to be unduly conspicuous in the fluids
and tissues of the body, and may do more or less damage prior to their
excretion through the kidneys. Further, it requires no imagination
to understand the constant strain upon the liver and kidneys, to say
nothing of possible influence upon the central and peripheral parts of
the nervous system, by these nitrogenous waste products which the body
ordinarily gets rid of as speedily as possible. They are an ever present
evil, but why increase them unnecessarily? This question brings us back
to the starting-point. What is the minimal proteid requirement for the
healthy man, or rather, how far can we safely and advantageously diminish
our proteid intake below the commonly accepted standards?
The question of safety is a pertinent one. Thus, Munk[23] some years
ago (1893) sounded a warning on this point which was later confirmed by
Rosenheim.[24] Both of these observers reported that in dogs fed for some
time on a low proteid diet, but with an abundance of carbohydrate and
fat, there was after some weeks (6-8) a loss of the power of absorption
from the alimentary tract, dependent not alone upon a changed condition
of the epithelial cells of the intestine, but also upon a diminished
secretion of the digestive juices, loss of body-weight, strength, and
vigor, followed speedily by death. If these results were really due
to the low proteid diet, they suggest a grave danger which must not be
lightly passed by. Jägerroos[25] has likewise observed, experimenting on
dogs, that there was, after some months, a striking disturbance of the
intestines on a low proteid intake, which, however, was eventually traced
to a distinct infection, and probably in no manner connected with the
diminished amount of proteid in the diet. In these various experiments
on dogs carried out by Munk, Rosenheim, and by Jägerroos, there was of
necessity great monotony in the diet, and in Munk’s experiments no fresh
meat at all was fed, but simply dried food. In other words, if the diet
was in any sense responsible for the poor health of the animals, it is
fully as plausible to attribute the results to the abnormal conditions
under which the animals were kept as to any specific effect due to the
low proteid intake. It is very essential that the food of dogs, as of
men, shall fulfil all ordinary hygienic conditions. It must be not only
of sufficient quantity for the true needs of the body, but it should
also have the necessary variety with reasonable degree of digestibility,
and proper volume or bulk. When these qualities are lacking, it is not
strange if deviations from the normal gradually develop. That the low
intake of proteid food could be responsible for the condition existing
in Munk’s and Rosenheim’s experiments is not plausible; a view which is
strongly reinforced by many observations, notably those of Albu[26] on a
woman thirty-seven years old and weighing 37.5 kilos, who had followed a
vegetarian diet for six years, and who while under Albu’s care for two
years consumed only 34 grams of proteid per day, the total fuel value of
the food being only 1400 calories per day. This woman was in nitrogenous
equilibrium on 5.4 grams of nitrogen, and on this diet had freed herself
from the illness to which she had long been subject.
Voit’s[27] vegetarian is described by Voit himself as a man twenty-eight
years old, weighing 57 kilos, well nourished, with well developed
muscles, etc. He had lived on a purely vegetable diet for three years,
and was found to be in nitrogenous equilibrium on 8.2 grams of nitrogen.
No mention is made of any disagreeable effects connected with this low
proteid ration, although persisted in for several years. Jaffa’s[28]
experiments and observations on the fruitarians and nutarians of
California “showed in every case (two women and three children) that
though the diet had a low protein and energy value, the subjects were
apparently in excellent health and had been so during the five to eight
years they had been living in this manner.” In comparing the income and
outgo of nitrogen on a diet composed mainly of nuts and fruits, it was
observed in two subjects that 8 grams of nitrogen were sufficient to
bring about nitrogen equilibrium, while with two other subjects on a like
diet the nitrogen required daily for equilibrium was about 10 grams. The
diet used in these experiments, however, was of necessity more or less
restricted in variety, and was without doubt somewhat monotonous. Jaffa
appears to agree with Caspari that the minimum amount of proteid required
daily varies with the individual, and may even vary with the same
individual at different times. Further, Jaffa, in harmony with Siven,
believes that after the body has suffered a loss of nitrogen, there is
at once an effort to attain nitrogenous equilibrium, and that any gain
of nitrogenous body material is a comparatively slow process. If this is
true, it is obvious that the living substance of the tissue protoplasm
must be _slowly_ formed from the proteid of the diet. This, says Jaffa,
should serve as a warning to anyone contemplating any appreciable
decrease in the proteid of the daily diet.
Another statement made by Jaffa may be quoted in this connection,
since it illustrates the attitude taken by many physiologists on this
question. “Even if it could be proved,” says Jaffa, “by a large number
of experiments that nitrogen equilibrium can be maintained on a small
amount of protein, it would still be a great question whether or not
it would be wise to do so. There must certainly be a constant effort
on the part of the human organism to attain this condition, and with
a low protein supply it might be forced to do so under conditions of
strain. In such a case the bad results might be slow in manifesting
themselves, but might also be serious and lasting. It has also been
suggested that when living at a fairly high protein level the body is
more resistant to disease and other strains than when the protein level
is low.” While these suggestions demand careful consideration, it is
equally evident that there is another side to the question, viz., the
possible danger to the body from the physiological action of the larger
amounts of nitrogenous waste products which result from an excess of
proteid food, and which float about through the system prior to their
excretion. In addition, we must not overlook the great loss of energy to
the body in handling and getting rid of the surplus of unnecessary food
of whatever kind introduced into the alimentary tract, to say nothing of
the danger of intestinal putrefaction and toxæmia when from any cause
the system loses its ability to digest and absorb the excess of food
consumed. Further, the possible strain on the kidneys and other organs
must not be overlooked. Hence we may well query on which side lies the
greater danger. To an unprejudiced observer, one not wedded to old-time
tradition, it would seem as if great effort was being made to sustain
the claims of a high-proteid intake. It is surely well to be careful,
but it is certainly not necessary to magnify imaginary dangers to the
extent of suppressing all efforts toward the establishment of possible
physiological economy.
In a paper read before the Physiological Section of the British Medical
Association in 1901 by Dr. van Someren, claim is made of the existence
of a reflex of deglutition, the proper working of which protects
from the results of malnutrition by preventing the intake of any
excess of food. Thorough mastication and insalivation aid in the more
complete utilization of the food and render possible great economy, so
that body-weight and nitrogen equilibrium are both maintained on an
exceptionally small amount of food. This principle had been worked out
by Mr. Horace Fletcher on himself in an attempt to restore his health to
a normal condition, with such beneficial results that he was speedily
restored to a state of exceptional vigor and well-being. Deliberation in
eating, necessitated by the habit of thorough insalivation, it is claimed
results in the occurrence of satiety on the ingestion of comparatively
small amounts of food, and hence all excess of food is avoided.
In the autumn of 1901, Mr. Fletcher and Dr. van Someren visited the
physiological laboratories of Cambridge University, and as stated by Sir
Michael Foster[29] the matter was more closely inquired into with the
assistance of physiological experts. Observations were carried out on
various individuals, and as stated by Professor Foster “the adoption of
the habit of thorough insalivation of the food was found in a consensus
of opinion to have an immediate and very striking effect upon appetite,
making this more discriminating, and leading to the choice of a simple
dietary, and in particular reducing the craving for flesh food. The
appetite, too, is beyond all question fully satisfied with a dietary
considerably less in amount than with ordinary habits is demanded.”...
“In two individuals who pushed the method to its limits it was found
that complete bodily efficiency was maintained for some weeks upon a
dietary which had a total energy value of less than one-half of that
usually taken, and comprised little more than one-third of the proteid
consumed by the average man.” Finally, says Foster, “it may be doubted if
continued efficiency could be maintained with such low values as these,
and very prolonged observations would be necessary to establish the
facts. But all subjects of the experiments who applied the principles
intelligently agreed in finding a very marked reduction in their needs,
and experienced an increase in their sense of well-being and an increase
in their working powers.”
In the autumn of 1902 and in the early part of 1903, Mr. Fletcher spent
several months with the writer, thereby giving an opportunity for
studying his habits of life. For a period of thirteen days in January
he was under constant observation in the writer’s laboratory, when it
was found that the average daily amount of proteid metabolised was 41.25
grams, his body-weight (75 kilos) remaining practically constant. Later,
a more thorough series of observations was made, involving a careful
analysis of the daily diet, together with analysis of the excreta. For
a period of six days the daily diet averaged 44.9 grams of proteid,
38.0 grams of fat, and 253 grams of carbohydrate, the total fuel value
amounting to only 1606 large calories per day. The daily intake of
nitrogen averaged 7.19 grams, while the daily output through the urine
was 6.30 grams and in the fæces 0.6 gram; _i. e._, a daily intake of 7.19
grams of nitrogen, with a total output of 6.90 grams, showing a daily
gain to the body of 0.29 gram of nitrogen, and this on a diet containing
less than half the proteid required by the Voit standard and having only
half the fuel value of the Voit diet. Further, it was found by careful
and thorough tests made at the Yale Gymnasium that Mr. Fletcher, in
spite of this comparatively low ration was in prime physical condition.
In the words of Dr. Anderson, the Director of the Gymnasium, “the case
is unusual, and I am surprised that Mr. Fletcher can do the work of
trained athletes and not give marked evidences of over-exertion.... Mr.
Fletcher performs this work with greater ease and with fewer noticeable
bad results than any man of his age and condition I have ever worked
with.”[30] It is not our purpose here to discuss how far these results
are due to insalivation, or the more thorough mastication of food.
The main point for us is that we have here a striking illustration of
the establishment of nitrogen equilibrium on a low proteid diet and
great physiological economy as shown by the low fuel value of the food
consumed, coupled with remarkable physical strength and endurance.
With data such as these before us we see the possible importance of a
fuller and more exact knowledge of true dietary standards. We find here
questions suggested, the answers to which are of primary importance in
our understanding of the nutritive processes of the body; greater ease
in the maintenance of health, increased power of resistance to disease
germs, duration of life increased beyond the present average, greater
physiological economy and greater efficiency, increased mental and
physical vigor with less expenditure of energy on the part of the body.
All these questions rise before us in connection with the possibility
of maintaining equilibrium on a lowered intake of food, especially
nitrogenous equilibrium, with a diminished consumption of proteid or
albuminous food. Is it not possible that the accepted dietary standards
are altogether too high?
It is of course understood that there can be no fixed dietary standard
suitable for all people, ages, and conditions of life. Dietary standards
at the best are merely an approximate indication of the amounts of food
needed by the body, but these needs are obviously changeable, varying
with the degree of activity of the body, especially the amount of
physical work performed, to say nothing of differences in body-weight,
sex, etc. Further, it is doubtless true that there is what may be called
a specific coefficient of nutrition characteristic of the individual, a
kind of personal idiosyncrasy which exercises in some degree a modifying
influence upon the character and extent of the changes going on in the
body. Still, with due recognition of the general influence exerted by
these various factors the main question remains, viz., how far the
usually accepted standards of diet are correct; or, in other words, is
there any real scientific ground for the assumption that the average
individual doing an average amount of work requires any such quantity
of proteid, or of total nutrients, as the ordinary dietetic standards
call for? Cannot all the real physiological needs of the body be met
by a greatly reduced proteid intake, with establishment of continued
nitrogenous equilibrium on a far smaller amount of proteid food than the
ordinary dietary standards call for, and with actual gain to the body?
Just here we may emphasize why prominence is given to the establishment
of _nitrogenous_ equilibrium, and why the proteid intake assumes a
greater importance than the daily amounts of fat and carbohydrate
consumed. Fats and carbohydrates when oxidized in the body are ultimately
burned to simple gaseous products, viz., carbonic acid and water. Hence,
these waste products are easily and quickly eliminated and cannot
exercise much deleterious influence even when formed in excess. To be
sure, there is waste of energy in digesting, absorbing, and oxidizing
the fats and carbohydrates when they are taken in excessive amounts.
Once introduced into the alimentary canal they must be digested,
otherwise they will clog the intestine or undergo fermentation, and so
cause trouble. Further, when absorbed they may be transformed into fat
and deposited in the various tissues and organs of the body; a process
desirable up to a certain point, but undesirable when such accumulation
renders the body gross and unwieldy. With proteid foods, on the other
hand, the story is quite different. These substances, when oxidized,
yield a row of crystalline nitrogenous products which ultimately pass out
of the body through the kidneys. Prior to their excretion, however, these
products—frequently spoken of as toxins—float about through the body and
may exercise more or less of a deleterious influence upon the system, or,
being temporarily deposited, may exert some specific or local influence
that calls for their speedy removal. Hence, the importance of restricting
the production of these bodies to the minimal amount, owing to their
possible physiological effect and the part they are liable to play in
the causation of many diseased conditions. Further, the elimination of
excessive amounts of these crystalline nitrogenous bodies through the
kidneys places upon these organs an unnecessary burden which is liable
to endanger their integrity and possibly result in serious injury, to say
nothing of an early impairment of function.
* * * * *
The present experiments were undertaken to throw light upon this broad
question of a possible physiological economy in nutrition, and with
special reference to the minimal proteid requirement of the healthy man
under ordinary conditions of life. The writer as a student of physiology
has always maintained that man is disposed to eat far more than the
needs of the body require, but his active interest in this problem
was aroused especially by his observations of Mr. Fletcher and the
marked physiological economy the latter was able to practice, not only
without detriment, but apparently with great gain to the body as regards
strength, vigor, and endurance, coupled with an apparent resistance to
disease. While Mr. Fletcher and Dr. Van Someren would doubtless emphasize
the importance of insalivation as a means of controlling the appetite and
thereby regulating the consumption of food in harmony with the real needs
of the body, it is of primary importance for the physiologist and for
mankind to know definitely how far it is possible to reduce the intake of
food with perfect safety and without loss of that strength, mental and
physical, vigor, and endurance which are characteristic of good health.
Further, it is equally plain that if there is possible gain to the body
from a practice of physiological economy in diet, we should know how far
this can be accomplished by simple restriction in the amount of food
without complicating the problem by other factors.
In planning the conduct of this series of experiments the writer
has clearly recognized that, while it may be possible, as previous
experiments have shown, to maintain body equilibrium and nitrogen
equilibrium on a low proteid diet for a brief period, this fact does not,
as Munk has previously pointed out, by any means establish the view that
such a diet will prove efficient in maintaining equilibrium for a long
period, or that bodily strength and vigor can be kept up and the proper
resistance to disease secured. Hence, it seemed necessary to so arrange
the experiments that they should continue not for a few days or weeks
merely, but through months and years. Further, it is very questionable
whether the restricted diet (restricted in variety) frequently made use
of for convenience in ordinary metabolism experiments is well adapted for
bringing out the best results. Hence, it was decided to avoid so far as
possible any monotony of diet, giving due recognition to the psychical
influences liable to affect secretion, digestion, etc., so admirably
worked out by Pawlow in his classical experiments on these subjects;
influences which are unquestionably of great importance in controlling
and modifying, in some measure at least, the nutritive changes in the
body. Again, it is evident that to have experiments of this character
broadly useful, they must be tried upon a large number of people and
under different conditions of life, in order to avoid so far as possible
the influence of personal idiosyncrasy and thereby escape misleading
conclusions.
The experiments have been conducted with three distinct types or classes
of individuals:
1st. A group of five men of varying ages, connected with the University
as professors and instructors; men who while leading active lives
have not engaged in very active muscular work. They were selected as
representatives of the mental worker rather than the physical worker,
although several of them in the performance of their daily duties had to
be on their feet in the laboratory a good portion of the day.
2d. A detail of thirteen men, volunteers from the Hospital Corps of
the United States Army and representatives of the moderate worker; men
who for a period of six months took each week day a vigorous amount of
systematic exercise in the gymnasium, in addition to the routine work
connected with their daily life as members of the United States Hospital
Corps. These men were of different nationalities, ages, and temperaments.
3d. A group of eight young men, students in the University, all
thoroughly trained athletes, and some of them with exceptional records in
athletic events.