Plant foods are the original source of all
food energy. For this reason they are some¬
times called primary foods. Animals are
valuable, however, in unlocking stores of
plant foods otherwise not available as human
food and changing them into palatable and
easily transported forms. Animal fats are
important sources of energy in the diet.
Animals also build from plant foods protein
compounds that may be used economically
(physiologically speaking) as sources of body¬
building materials.
The energy in fuels-wood, coal, and oil-is
all originally of plant origin, and the energy
in them came from the sun entrapped through
the life activity of the plant. Although the
chemist may now build, or synthesize, or¬
ganic compounds in the laboratory, the
organic or energy-containing materials are as
yet largely the result of life.
Calories. To measure the energy value of
foods, a heat unit called the "calorie” is used.
A large calorie, or kilogram-calorie, is the
amount of heat required to raise one kilo¬
gram of water one degree centigrade.
The determination of the calorie content
of foods is based upon the assumption that
these compounds yield the same amount of
energy when burned in the body as when
burned outside. Carbohydrates and fats burn
completely in the body, yielding carbon
dioxide and water. Protein, on the other
hand, is not completely burned in the body,
but always leaves a nitrogenous residue which
represents a certain amount of energy. In
determining the fuel value of protein foods,
it is necessary to correct for this loss. This is^
done by subtracting from the total amount
of energy yielded by burning protein outside
the body the amount of energy represented
by the urea and other nitrogenous materials
remaining when that same amount of protein
is metabolized in the body.
A calorimeter is used to measure the cal¬
ories given off when a weighed quantity of
food is burned under controlled conditions.
By the use of this instrument the calorie con¬
tent of the food nutrients has been estab¬
lished. After the necessary corrections, it is
estimated that, when burned in the body,
each gram of carbohydrate yields four cal¬
ories; each gram of protein, four calories;
and each gram of fat, nine calories. By use
of these values, it is possible to compute the
calorie content of any food the composition
of which is known. The fuel value per pound
of the common foods given in tables of food
composition is usually computed rather than
determined directly.
BUILDING AND REGULATING FOODS
The regulating function of food is carried
out largely by maintenance of the normal
composition of important tissues and fluids.
[ii]
T he same food components serve both build¬
ing and regulating functions. Active body
tissues are composed of approximately two-
thirds water and one-third protein. The
body as a whole contains three to four per
cent ash or mineral substances. Fats and car¬
bohydrates are found in the body in varying
amounts depending upon the plane of nu¬
trition. Small amounts of these are essential.
Page 9
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
Plant foods are the original source of all food energy. For this reason they are some¬ times called primary foods. Animals are valuable, however, in unlocking stores of plant foods otherwise not available as human food and changing them into palatable and easily transported forms. Animal fats are important sources of energy in the diet. Animals also build from plant foods protein compounds that may be used economically (physiologically speaking) as sources of body¬ building materials.
The energy in fuels-wood, coal, and oil-is all originally of plant origin, and the energy in them came from the sun entrapped through the life activity of the plant. Although the chemist may now build, or synthesize, or¬ ganic compounds in the laboratory, the organic or energy-containing materials are as yet largely the result of life.
Calories. To measure the energy value of foods, a heat unit called the "calorie” is used.
A large calorie, or kilogram-calorie, is the amount of heat required to raise one kilo¬ gram of water one degree centigrade.
The determination of the calorie content of foods is based upon the assumption that these compounds yield the same amount of energy when burned in the body as when burned outside. Carbohydrates and fats burn completely in the body, yielding carbon dioxide and water. Protein, on the other hand, is not completely burned in the body, but always leaves a nitrogenous residue which represents a certain amount of energy. In determining the fuel value of protein foods, it is necessary to correct for this loss. This is done by subtracting from the total amount of energy yielded by burning protein outside the body the amount of energy represented by the urea and other nitrogenous materials remaining when that same amount of protein is metabolized in the body.
A calorimeter is used to measure the cal¬ ories given off when a weighed quantity of food is burned under controlled conditions. By the use of this instrument the calorie con¬ tent of the food nutrients has been estab¬ lished. After the necessary corrections, it is estimated that, when burned in the body, each gram of carbohydrate yields four cal¬ ories; each gram of protein, four calories; and each gram of fat, nine calories. By use of these values, it is possible to compute the calorie content of any food the composition of which is known. The fuel value per pound of the common foods given in tables of food composition is usually computed rather than determined directly.
BUILDING AND REGULATING FOODS
The regulating function of food is carried out largely by maintenance of the normal composition of important tissues and fluids.
[ii]
T he same food components serve both build¬ ing and regulating functions. Active body tissues are composed of approximately twothirds water and one-third protein. The body as a whole contains three to four per cent ash or mineral substances. Fats and car¬ bohydrates are found in the body in varying amounts depending upon the plane of nu¬ trition. Small amounts of these are essential.