FOOD AND FOOD-SUBSTANCES.
There are two kinds of food: 1. Those food substances that are derived
from the animal kingdom; and, 2. Food substances that are derived
from the vegetable kingdom.
Food is taken into the system to replace the material expended by
the human body, or the waste products which are thrown off from the
master tissues.
Definition: Food may be defined to be any natural substance, vegetable
or animal, recognized as such, that has undergone neither the process
of fermentation nor that of putrefaction.
Food may be considered in its relation to two purposes--the nutrition
of the tissues, and the production of heat. Under the first of these
heads will be included many other allied functions, as for example,
secretion and generation; and under the second, not the production
of heat only as such, but of all other forces correlated with it,
which are manifested by the living body.
Foods derived from the animal kingdom are called nitrogenous
substances, or azotized. They are also known by the name of
proteids. These are mainly derived from meat, milk, eggs, etc. Of
several we will examine the chemical composition.
It will be well to state in general terms that all food substances
contain in their composition from two-thirds to three-fourths, or
even more, of water--some more, some less.
Proteids.
Albumen. Caseine. Syntonin. Gluten. Gelatine.
Carbon, 72
Hydrogen, 112
Oxygen, 23
Nitrogen, 18
Sulphur, 1
Phosphorus, R. 2
Non-Nitrogenous Substances.
Carbon. Hydrogen. Oxygen.
1. Starch (amyloids), 18 30 15
Sugar cane, 12 22 11
2. Oils and fats composed of stearic acid 18 36 2
of mutton or beef,
3. Mineral--Saline matters, as chloride of
sodium, phosphate of lime.
Animals cannot subsist on any but organic substances, and these must
contain the elements which are naturally combined with them--in
other words, not even organic compounds are nutritive unless they
are supplied in their natural state. Pure fibrine, pure gelatine,
and other principles purified from the substances naturally
mingled with them, are incapable of supporting life for more than a
brief time. Moreover, health cannot be maintained by any number of
substances derived exclusively from one only of the two chief groups
of elementary principles mentioned above. A mixture of nitrogenous
and non-nitrogenous organic substances, together with the inorganic
principles which are severally contained in them, is essential to the
well-being, and generally even to the existence, of an animal. The
truth of this is demonstrated by experiments performed for the purpose;
and is also well illustrated by the composition of the food prepared
by nature as the exclusive source of nourishment to the young mammals,
namely milk. The composition of milk is:
Human. Cow's.
Water, 890 858
Solids, 110 142
---- ----
1000 1000
Caseine, 35 68
Butter, 25 38
Sugar (with extracts), 48 30
Salts, 2 6
--- ---
110 142
Carb. Hyd. Nit. Oxy. Sulph. R (unknown).
Caseine, 72 112 18 23 1 2
In milk, it will be seen from the preceding table, the albuminous
group of aliments is represented by the caseine, the oleaginous by the
butter, the aqueous by the water, the saccharine by the sugar of milk.
Let us compare the composition of these four organic substances
and water:
Oxy. Hyd. Carb. Nitr. Sulph. R (unknown
element).
Water, 1 2
Sugar, OH2+ 11 22 12
Caseine, 23 112 72 18 1 2
Olein, 6 38 21
Among the salts of milk are phosphate of lime, alkaline and other
salts, and a trace of iron; so that it may be briefly said to include
all the substances which the tissues of a growing animal need for their
nutrition and which are required for the production of animal heat.
The yolk and albumen of eggs stand in the same relation as food for the
embryos of oviparous animals, that milk does to the young mammalia;
and affords another example of mixed food being provided as the most
perfect nutrition. The composition of fowl's egg is:
White. Yolk.
Water, 80.0 53.73
Albumen, 15.5 17.47
Mucus, 4.5 yellow oil 28.75
Salts, 4.0 6.0
The food substances. 1. Amyloids, starch and sugars. Starch is derived
from grain and vegetables, as wheat, barley, rye, oats, corn, rice,
sago, tapioca, beans, peas, etc.
The vegetables contain from 75 to 90 per cent of water. Starch and
sugars are derived from such as potatoes, turnips, carrots, beets,
etc., etc.
The fruits are largely composed of water, sugars, and acids.
All these classes of food contain only three elements.--Starch:
Carbon. Hydrogen. Oxygen.
18 30 15
In their composition we have fifteen molecules of water presented
carrying eighteen atoms of carbon. Sugar:
Carbon. Hydrogen. Oxygen.
12 22 11
In this case again we have eleven molecules of water carrying twelve
atoms of carbon. This is the chemical composition of starch and
sugar food.
2. Fats are also composed of three elements only--carbon, hydrogen,
and oxygen. Take the fat of mutton or pork:
Carbon. Hydrogen. Oxygen.
21 40 1
All other animal oils and fats are composed of these three elements
only.
3. Albuminous substances--meats, beef, mutton, veal, pork, birds,
and fish, of all descriptions.
4. Besides these, mineral salts, already mentioned.
5. And lastly, water--of which by far the greatest quantity is
consumed.
The quantity of food ought to be in amount sufficient to replace the
waste products of the body. An amount should be taken into the system
equal in kind and quantity to the material expended.
Since we know the amount of carbon, hydrogen, nitrogen, oxygen, and
the salts that are excreted by the kidneys, skin, and lungs, we may
easily calculate the amount of various kinds of food needed to replace
them. The outcome being known, the income can be regulated accordingly.
The expenditure or waste, we have seen, in daily loss amounts in carbon
to about 4,500 grains, and in nitrogen to 300 grains; besides a certain
quantity of water, etc. We therefore require starchy substances, meat
and fat, water, etc., to replace the quantity lost. Bread, for example,
contains 30 per cent of carbon and 1 per cent of nitrogen. If bread
alone, therefore, were taken as food, a man would require in order
to obtain the requisite nitrogen 30,000 grains, containing of carbon,
9,000 grains; of nitrogen, 300 grains--an excess of carbon above the
amount required of 4,500 grains. But a combination of bread and meat
would supply much more economically what was necessary:
Carbon. Nitrogen.
15,000 grains of bread (rather more
than 2 pounds) contains 4,500 grs. 150 grs.
5,000 grains of meat (about 3/4
pounds) contains 500 150
----- ---
5,000 300
So that 3/4 pounds meat and 2 pounds of bread, or its equivalent,
would supply the needful carbon and nitrogen with but little waste.
From all these facts it will be plain that a mixed diet is the best
and most economical for man; and the result of experience entirely
coincides with what might have been anticipated on theoretical
grounds only.
The quality and quantity of foods to be taken depends largely upon
their digestibility.
The quantity of food necessary for a healthy man taking free exercise
in the open air is as follows:
Meat 16 ounces or 1 pound avoir.
Bread and all other 19 ,, ,, 1.19 ,, ,,
carbohydrates,
Fat, butter, 3 1/2 ,, ,, 0.22 ,, ,,
Water 52 ,, ,, 3.38 ,, ,,
The quantity and quality of food taken into the system every
twenty-four hours, should depend upon the amount and kind of labor
done, whether muscular or nervous, whether sitting or not, inactive or
active, whether indoors or out of doors; upon the kind of atmosphere we
breathe; upon season and climate, etc.; also upon the opportunities we
have of throwing off the surplus carbon and nitrogen that the system
has been overcrowded with.
These conditions determine the proper variations of the income, since
that has to be regulated and corrected by the outcome, and amounts
after all to just so much carbon, hydrogen, oxygen, nitrogen, sulphur,
phosphorus, saline matter, and water as are contained in the proteids,
fats, carbohydrates, salts, and water.
It matters little how food is prepared. The main feature is that the
supply is equal to the loss, of good and wholesome quality. Whether
the food is manipulated by an artistic $10,000 cook or by a plain,
clean housewife, the result is the same. Whether the special sense of
taste, the gustatory nerve, has or has not undergone a high course
of training and education, the fact remains that all that can be
supplied is the necessary material that has been expended by the work
and labor done by the muscular and nervous tissues.
The subjoined results, selected from Boussingault, exhibit in a tabular
form the relative quantity of organic and inorganic constituents in
several kinds of herbage compared in several cases with the root or
grain. The water was previously driven off by thorough drying:
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Leaves of Root of
Mangel- Mangel- Potato Pea Clover Wheat
Wurzel. Wurzel. Tops. Potatoes. Straw. Peas. Hay. Straw. Wheat.
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Carbon 38.10 42.75 44.80 43.72 45.80 46.06 47.53 48.48 46.10
Hydrogen 5.10 5.77 5.10 6.00 5.00 6.09 4.69 5.41 5.80
Oxygen 30.80 43.58 30.50 44.88 35.57 40.53 37.96 38.79 43.40
Nitrogen 4.50 1.66 2.30 1.50 2.31 4.18 2.06 0.35 2.27
Ashes 21.50 6.24 3.90 3.90 11.32 3.14 7.76 6.97 2.43
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100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00
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Subjoined is a table from the same work of the percentage of mineral
substances taken up from the soil by various plants:
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Substances Acids Oxide of
Which -------------------------------- Iron, Charcoal,
Yield Ammonia moisture,
Ashes. Carbonic. Sulphuric. Phosphoric. Chlorine. Lime. Magnesia. Potash. Soda. Silica. etc. and loss.
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Potatoes 13.4 7.1 11.3 2.7 1.8 5.4 51.5 traces 5.6 0.5 0.7
Mangel-
Wurzel 16.1 1.6 6.1 5.2 7.0 4.4 39.0 6.0 8.0 2.5 4.2
Turnips 14.0 10.9 6.0 2.9 10.9 4.3 39.7 4.1 6.4 1.2 5.5
Potato
Tops 11.0 2.2 10.8 1.6 2.3 1.8 44.5 traces 13.0 5.2 7.6
Wheat 0.0 1.0 47.0 traces 2.9 15.9 29.5 traces 1.3 0.0 2.4
Wheat
Straw 0.0 1.0 3.1 0.5 8.5 5.0 9.2 0.3 67.6 1.0 3.7
Oats 1.7 1.0 14.9 0.5 3.7 7.7 12.9 0.0 53.3 1.3 3.0
Oat Straw 3.2 4.1 3.0 4.7 8.3 2.8 24.5 4.4 40.0 2.1 2.9
Clover 25.0 2.5 6.3 2.6 24.6 6.3 26.6 0.5 5.3 0.3 0.0
Pease 0.5 6.7 30.1 1.1 10.1 11.9 35.3 2.5 1.5 traces 2.3
French
Beans 3.3 1.3 26.8 0.1 5.8 11.5 49.1 0.0 1.0 traces 1.1
Horse
Beans 1.0 1.6 34.2 0.7 5.1 8.6 45.2 0.0 0.5 traces 3.1
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