Digestion of Food. There are certain def¬
inite forms in which food nutrients are ab¬
sorbed and carried to the body tissues, and
the whole digestive process functions to
break down complex foods into these forms.
This breaking down, or digestion, is accom¬
plished by means of chemical substances
called "enzymes.” That part of the body set
aside for digestion, the alimentary tract, is
highly specialized in its different portions.
Each portion has its special job, and certain
glands, or groups of cells, secrete digestive
juices containing the enzymes needed to do
the specific work of that portion.
Enzymes are substances produced by liv¬
ing cells which bring about chemical changes
in other compounds without being used up
themselves. Chemists call such a substance a
"catalytic agent.”
Digestive enzymes are specific in action.
The available data on food composition are as¬
sembled in this bulletin: C. Chatfield and G. Adams,
Proximate Composition of American Food Materials ,
United States Department of Agriculture, Circular
No. 549, 1940.
Each enzyme acts on only one food nutrient
or group of nutrients. For example, in the
intestinal secretion three sugar-splitting en¬
zymes are present: sucrase, which splits
sucrose, or cane sugar; maltase, which splits
maltose, or malt sugar; and lactase, which
splits lactose, or milk sugar. On the other
hand, an enzyme such as pepsin in the gastric
juice will digest any protein, but will act only
on proteins.
The first test of the usefulness of any ma¬
terial as food is whether the digestive tract is
equipped with an enzyme to change it into a
form that can be absorbed and used by body
tissues. Studies of certain carbohydrates,
such as cellulose, Irish moss, and agar agar,
present in some foods, have shown that the
human digestive tract has no enzymes to
digest them. The same is true of mineral oils.
These oils are high in energy value but are
useless as food, since the digestive tract is not
equipped with an enzyme to break them
down into a form that can be used. Both
these groups of substances pass through the
intestinal tract unchanged. Since they in¬
crease the bulk and improve the consistency
of the intestinal residue, they frequently are
used in cases of constipation.
Ease of Digestion. Some foods are di¬
gested more quickly than others. Certain
conditions in the food or in the digestive
tract may retard digestion to such a degree as
to cause discomfort. Right conditions facili¬
tate the digestion of any food.
Palatability has an important part to play
in initiating digestion. Appetizing odors and
the sight or taste of desirable food may start
the flow of the digestive juices before there
has been any physical contact of the food
with the digestive area. Even the thought of
appetizing food is said to "make the mouth
water.” Well-prepared, palatable, tempting-
looking food is an important factor in good
digestion.
Certain constituents of food affect the
[8]
flow of the digestive juices after entrance into
the stomach. The extractives in clear meat
soups stimulate chemically the flow of the
digestive juices. For these reasons flavorful
fruits and well-flavored soups are good
starters for a meal. On the other hand, fats
tend to retard the flow of digestive juices, so
that they should never be used extensively
in the first part of the meal.
Page 6
Presented as published in 1935. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
AI-modernized reading of the original text
Digestion of Food. There are certain definite forms in which food nutrients are ab¬ sorbed and carried to the body tissues, and the whole digestive process functions to break down complex foods into these forms. This breaking down, or digestion, is accom¬ plished by means of chemical substances called "enzymes.” That part of the body set aside for digestion, the alimentary tract, is highly specialized in its different portions. Each portion has its special job, and certain glands, or groups of cells, secrete digestive juices containing the enzymes needed to do the specific work of that portion.
Enzymes are substances produced by liv¬ ing cells which bring about chemical changes in other compounds without being used up themselves. Chemists call such a substance a "catalytic agent.”
Digestive enzymes are specific in action.
The available data on food composition are as¬ sembled in this bulletin: C. Chatfield and G. Adams, Proximate Composition of American Food Materials , United States Department of Agriculture, Circular No. 549, 1940.
Each enzyme acts on only one food nutrient or group of nutrients. For example, in the intestinal secretion three sugar-splitting en¬ zymes are present: sucrase, which splits sucrose, or cane sugar; maltase, which splits maltose, or malt sugar; and lactase, which splits lactose, or milk sugar. On the other hand, an enzyme such as pepsin in the gastric juice will digest any protein, but will act only on proteins.
The first test of the usefulness of any ma¬ terial as food is whether the digestive tract is equipped with an enzyme to change it into a form that can be absorbed and used by body tissues. Studies of certain carbohydrates, such as cellulose, Irish moss, and agar agar, present in some foods, have shown that the human digestive tract has no enzymes to digest them. The same is true of mineral oils. These oils are high in energy value but are useless as food, since the digestive tract is not equipped with an enzyme to break them down into a form that can be used. Both these groups of substances pass through the intestinal tract unchanged. Since they in¬ crease the bulk and improve the consistency of the intestinal residue, they frequently are used in cases of constipation.
Ease of Digestion. Some foods are di¬ gested more quickly than others. Certain conditions in the food or in the digestive tract may retard digestion to such a degree as to cause discomfort. Right conditions facili¬ tate the digestion of any food.
Palatability has an important part to play in initiating digestion. Appetizing odors and the sight or taste of desirable food may start the flow of the digestive juices before there has been any physical contact of the food with the digestive area. Even the thought of appetizing food is said to "make the mouth water.” Well-prepared, palatable, tempting-looking food is an important factor in good digestion.
Certain constituents of food affect the
[8]
flow of the digestive juices after entrance into the stomach. The extractives in clear meat soups stimulate chemically the flow of the digestive juices. For these reasons flavorful fruits and well-flavored soups are good starters for a meal. On the other hand, fats tend to retard the flow of digestive juices, so that they should never be used extensively in the first part of the meal.