Before proceeding with a detailed account of the experimental work, it
may be well again to emphasize that what is especially desired is to
ascertain how far, if any, the intake of proteid food can be diminished
without detriment to the body, _i. e._, with maintenance of nitrogen
and body equilibrium and without impairment of bodily and mental vigor.
Further, if a lower proteid standard than that generally adopted can be
established, it is desirable to ascertain whether it can be maintained
indefinitely, or for a long period of time, without loss of strength
and vigor. Obviously, it is of primary importance that we should know
quite definitely what the minimal proteid requirement of the healthy man
per kilo of body-weight really is, and the experimental work about to
be detailed has aimed especially to determine whether it is possible to
materially lower the amount of daily proteid food, without detriment to
the bodily health and with maintenance of physical and mental vigor.
The writer, fully impressed with his responsibility in the conduct of an
experiment of this kind, began with himself in November, 1902. At that
time he weighed 65 kilos, was nearly 47 years of age, and accustomed
to eating daily an amount of food approximately equal to the so-called
dietary standards. Recognizing that the habits of a lifetime should not
be too suddenly changed, a gradual reduction was made in the amount of
proteid or albuminous food taken each day. In the writer’s case, this
resulted in the course of a month or two in the complete abolition of
breakfast, except for a small cup of coffee. A light lunch was taken at
1.30 P. M., followed by a heavier dinner at 6.30 P. M. Occasionally,
however, the heartier meal was taken at noontime, as the appetite
suggested. It should be added that the total intake of food was gradually
diminished, as well as the proteid constituents. There was no change,
however, to a vegetable diet, but a simple introduction of physiological
economy. Still, there was and is now a distinct tendency toward the
exclusion of meat in some measure, the appetite not calling for this
form of food in the same degree as formerly. At first, this change to a
smaller amount of food daily was attended with some discomfort, but this
soon passed away, and the writer’s interest in the subject was augmented
by the discovery that he was unquestionably in improved physical
condition. A rheumatic trouble in the knee joint, which had persisted
for a year and a half and which only partially responded to treatment,
entirely disappeared (and has never recurred since). Minor troubles, such
as “sick headaches” and bilious attacks, no longer appeared periodically
as before. There was greater appreciation of such food as was eaten; a
keener appetite and a more acute taste seemed to be developed, with a
more thorough liking for simple foods. By June, 1903, the body-weight had
fallen to 58 kilos.
During the summer the same simple diet was persisted in—a small cup of
coffee for breakfast, a fairly substantial dinner at midday and a light
supper at night. Two months were spent in Maine at an inland fishing
resort, and during a part of this time a guide was dispensed with and
the boat rowed by the writer frequently six to ten miles in a forenoon,
sometimes against head winds (without breakfast), and with much greater
freedom from fatigue and muscular soreness than in previous years on a
fuller dietary. The test of endurance and fitness for physical work which
the writer thus carried out “on an empty stomach” tended to strengthen
the opinion that it is a mistake to assume the necessity for a hearty
meal because heavy work is about to be done. It is certainly far more
rational from a physiological standpoint to leave the hearty meal until
the day’s work is accomplished. We seemingly forget that the energy
of muscular contraction comes not from the food-stuffs present at the
time in the stomach and intestinal tract, but rather from the absorbed
material stored up in the muscles and which was digested and absorbed a
day or two before. Further, it is to be remembered that the very process
of digestion draws to the gastro-intestinal tract a large supply of
blood, and that a large amount of energy is needed for the processes
of secretion, digestion, absorption, and peristalsis, which are of
necessity incited by the presence of food in the stomach and intestine,
thereby actually diminishing the amount of energy available at the place
where it is most needed. Why, then, draw upon the resources of the body
just at a time, or slightly prior to the time, when the work we desire
to perform, either muscular or mental, calls for a copious blood supply
in muscle or brain, and when all available energy is needed for the task
that is to be accomplished?
We are too wont to compare the working body with a machine, the boiler,
engine, etc., overlooking the fact that the animal mechanism differs
from the machine in at least one important respect. When we desire
to set machinery in operation we must get up steam, and so a fire is
started under the boiler and steam is generated in proportion as fuel
is burned. The source of the energy made use of in moving the machinery
is the extraneous combustible material introduced into the fire-box,
but the energy of muscular contraction, for example, comes not from
the oxidizable food material in the stomach, but from the material of
the muscle itself. In other words, in the animal body it is a part of
the tissue framework, or material that is closely incorporated with
the framework, that is burned up, and the ability to endure continued
muscular strain depends upon the nutritive condition of the muscles
involved, and not upon the amount of food contained in, or introduced
into, the stomach. All physiologists will, I think, acknowledge the
soundness of this reasoning, but how few of us apply the principle in
practice. It is perfectly logical to begin the work of the day with a
comparatively empty stomach,—after we have once freed ourselves from the
habit of a hearty breakfast,—and in the writer’s experience both mental
and physical work have become the easier from this change of habit. The
muscle and the brain are given opportunity to repair the waste they have
undergone, by the taking of food at times when the digestive processes
will not draw upon the energy that in activity is needed elsewhere.
Further, it is easy to understand why on a restricted diet, especially
of proteid foods, there should be a diminished sense of fatigue in
connection with vigorous or continued muscular work, and why at the
same time there should be an increased power of endurance, with actual
increase of strength. With a diminished intake of proteid food there is
a decreased formation of crystalline nitrogenous waste products, such as
uric acid and the purin bases, to say nothing of other bodies less fully
known, which circulating through the system are undoubtedly responsible,
in part at least, for what we term fatigue. We need not consider here
whether the sense of fatigue is due to an action of these substances upon
the muscles themselves, upon the motor nerves or their end-plates, or
upon the central nervous system; it is enough for the present purpose to
emphasize the probable results of their presence in undue amount. Lastly,
we may emphasize what is pretty clearly evident to-day, viz., that the
energy of muscular contraction comes preferably from the oxidation, not
of the nitrogenous or proteid constituents of the muscles, but of the
non-nitrogenous components of the tissue; another reason why excess
of proteid food may be advantageously avoided. Moreover, proteid food
stimulates body metabolism in general, and hence undue amounts of proteid
in the diet augment unnecessarily the metabolism or combustion of the
non-nitrogenous material of the muscle, thereby destroying what would
otherwise be preserved as a source of energy in muscular contraction,
when the muscles are called upon for the performance of their daily
functions.
On the writer’s return to New Haven in the fall of 1903, he was surprised
to find that his body-weight was practically the same as early in July.
In the period between November, 1902, and July, 1903, the body had lost
8 kilos under the gradual change of diet, but from July to October,
1903, the weight had apparently remained stationary, from which it might
fairly be assumed that the body had finally adjusted itself to the new
conditions.
What now was the condition of the body as regards nitrogen metabolism? To
answer this question the entire twenty-four hours’ urine was collected
practically every day, from October 13, 1903, to June 28, 1904,
representing a period of nearly nine months. This daily output through
the kidneys was analyzed each day with special reference to the total
nitrogen,[31] as a measure of the amount of proteid material metabolized.
Total volume of the urine, specific gravity, uric acid, phosphoric acid,
indican, and other points were also considered, the more important
results being indicated in the following tables.