Principles of nutrition and nutritive value of food. Page: 23
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Suppose, for instance, that 15 per cent of the protein in a specimen
of bread is excreted, then 85 per cent remains for the use of the body.
If the bread has 8.4 per cent of protein, 100 pounds will have 8.4
pounds, of which 85 per cent or 7.1 pounds will be utilized by the
body. Table III (p. 28) gives details regarding the proportions of
digestible nutrients in different food materials.
EASE AND QUICKNESS OF DIGESTION.
The terms digestible, indigestible, etc., as here used refer simply to
the food which is or is not available for the general nourishment of
the body after the process of digestion is completed. In common
parlance, however, they are used more loosely as referring to the ease
and quickness of digestion, and to the general healthfulness of food.
One kind of food, bread, for instance, is spoken of as "simple " and
" digestible," and another, like fruit cake, as "rich " and "indigestible."
There is often much practical truth behind such statements,
though little is definitely known concerning the time or labor required
. to digest different kinds of food.
Among the earliest and most famous experiments concerning the
time required for digestion in the stomach are those made by Dr.WilHam
Beaumont, U. S. A., between 1825 and 1833. His subject was a
French-Canadian trapper, a man quite normal except for an aperture
through the abdomen into the stomach made by a gunshot wound, and
closed only by a valve which had developed over it. By pressing the
valve inward the contents of the stomach could be observed or
removed at will, thus affording excellent opportunity to study the
action of the gastric juice. Dr. Beaumont fed the man on various
diets, and noted the different conditions accompanying each. The
book in which he describes his experiments' contains a table of the
average time required for the stomach to digest various articles of
diet, from which many of the statements still current concerning the
relative digestibility of different foods are taken.
One of Dr. Beaumont's general deductions was that most of the
common foods required from 2 to 4 hours. He says further:
"The time required for the digestion of food is various, depending
upon the quantity and quality of the food, state of the stomach, etc.,
but the time ordinarily required for the disposal of a moderate meal
of the fibrous parts of meat, with bread, etc., is from 3 to 3J hours."
Valuable and interesting as Dr. Beaumont's book undoubtedly is, its
conclusions can not be taken as final because he does not state the
amounts of food consumed. The science of nutrition in its development
has also shown many errors in the reasoning. It should in
William Beaumont, The Physiology of Digestion, with Experiments on the Gastric
Juice. 2d ed. Burlington, Vt., 1847.
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United States. Department of Agriculture. Principles of nutrition and nutritive value of food., book, 1902; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc6413/m1/23/: accessed March 6, 2021), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.