THE FOOD-FUEL OF THE BODY-ENGINE
WHAT KIND OF FOOD SHOULD WE EAT?
Generally speaking, our Appetites will Guide us. Our whole body is an
ingenious machine for catching food, digesting it, and turning the
energy, or fuel value, which it contains, into life, movement, and
growth.
Naturally, two things follow: first, that the kind and amount of food
which we eat is of great importance; and second, that from the millions
of years of experience that the human body has had in trying all sorts
of foods, it has adapted itself to certain kinds of food and developed
certain likes and dislikes which we call _appetites_. Those who happened
to like unhealthy and unwholesome foods were poisoned, or grew thin and
weak and died off, so that we are descended solely from people who had
sound and reliable food appetites; and, in the main, what our instincts
and appetites tell us about food is to be depended upon.
The main questions which we have to consider are: How much of the
different kinds of food it is best for us to eat, and in what
proportions we should use them. Both men and animals, since the world
began, have been trying to eat and digest almost everything that they
could get into their mouths. And what we now like and prepare as foods
are the things which have stood the test, and proved themselves able to
yield strength and nourishment to the body. So practically every food
that comes upon our tables has some kind of real food value, or it
wouldn't appear there.
The most careful study and analysis have shown that almost every known
food has some peculiar advantage, such as digestibility, or cheapness,
or pleasant taste as flavoring for other more nutritious, but less
interesting, foods. But some foods have much higher degrees of
nutritiousness or digestibility or wholesomeness than others; so that
our problem is to pick out from a number of foods that "taste good" to
us, those which are the most nutritious, the most digestible, and the
most wholesome, and to see that we get plenty of them. It is not that
certain foods, or classes of food, are "good," and should be eaten to
the exclusion of all others; nor that certain foods, or classes of food,
are "bad," and should be excluded from our tables entirely; but that
certain foods are more nutritious, or more wholesome, than others; and
that it is best to see that we get plenty of the former before indulging
our appetites upon the latter.
Beware of Tainted Food. The most dangerous fault that any food can
have is that it shall be tainted, or spoiled, or smell bad. Spoiling, or
tainting, means that the food has become infected by some germs of
putrefaction, generally _bacteria_ or _moulds_ (see chapter XXVI). It is
the poisons--called _ptomaines_, or _toxins_--produced by these germs
which cause the serious disturbances in the stomach, and not either the
amount or the kind of food itself. Even a regular "gorge" upon early
apples or watermelon or cake or ice cream will not give you half so bad,
nor so dangerous, colic as one little piece of tainted meat or fish or
egg, or one cupful of dirty milk, or a single helping of cabbage or
tomatoes that have begun to spoil, or of jam made out of spoiled berries
or other fruit. This spoiling can be prevented by strict cleanliness in
handling foods, especially milk, meat, and fruit; by keeping foods
screened from dust and flies; and by keeping them cool with ice in
summer time, thus checking the growth of these "spoiling" germs. The
refrigerator in the kitchen prevents colic or diarrhea, ice in hot
weather is one of the necessaries of life. Smell every piece of food to
be eaten, in the kitchen before it is cooked, if possible; but if not,
at the table avoid everything that has an unpleasant odor, or tastes
queer, and you will avoid two-thirds of the colic, diarrhea, and bilious
attacks which are so often supposed to be due to eating too much.
[Illustration: A CHEAP HOME-MADE ICE BOX
This should not cost over twenty-five cents. The sketch shows an
ordinary soap box; inside is a tin pail surrounded by a sheet of tin, so
that there is a circular air space between the pail and the sheet of
tin. Sawdust is packed around the tin, and cracked ice (two cents a day)
fills the tin pail around the milk bottle. The newspapers inside the
cover help to keep out the warmth of the outside air. Recommended by the
Boards of Health of New York City and Chicago.]
Variety in Food is Necessary. Man has always lived on, and apparently
required, a great variety of foods, animal and vegetable--fish and
flesh, nuts, fruit, grains, fat, sugar, and vegetables. Indeed, it was
probably because man could live on anything and everything that he was
able to survive in famines and to get so far ahead of all other sorts of
animals.
We still need a great variety of different sorts of food in order to
keep our health; so our tendency to become tired of a certain food,
after we have had it over and over and over again, for breakfast,
dinner, and supper, is a sound and healthy one. There is no "best food";
nor is there any one food on which we can live and work, as an engine
will work all its "life" on one kind of coal, wood, or oil. No one kind
of food contains all the stuffs that our body is made of and needs, in
exactly the right proportions. It takes a dozen or more different kinds
of food to supply these, and the body picks out what it wants, and
throws away the remainder.
Even the best and most nutritious and digestible single food, like meat,
or bread and butter, or sugar, is not sufficient by itself; nor will it
do for every meal in the day, or every day in the week. We must eat
other things with it; and we must from time to time change it for
something which may even be not quite so nutritious, in order to give
our body the opportunity to select from a great variety of foods the
particular things which its wonderful instincts and skill can use to
build it up and keep it healthy. This is why every grocery store, every
butcher shop, every fish market, and every confectioner's shows such a
great variety of different kinds of foods put up and prepared in all
sorts of ways. Although nearly two-thirds of the actual fuel which we
put into our body-boilers is in the form of a dozen or fifteen great
staple foods, like bread, meat, butter, sugar, eggs, milk, potatoes, and
fish, yet all the lighter foods, also, are needed for perfect health.
It is possible, by careful selection, and by taking a great deal of
trouble, to supply all the elements of the body from animal foods alone,
or from vegetable foods alone. But practically, it has everywhere, and
in all ages, been found that the best and most healthful diet is a
proper combination of animal and vegetable foods. Our starches, for
instance, which furnish most of our fuel,--though they give us
_comparatively little_ to _build up_, or _repair_, the body with,--are
found, as we have seen, in the vegetable kingdom, in grains and fruits;
while most of our proteins and fats, which chiefly give us the materials
with which to build up, or repair, the body, are found in the animal
kingdom. There is no advantage whatever in trying to exclude either
animal food or vegetable food from our dietary. Both animal and
vegetable foods are wholesome in their proper place, and their proper
place is on the table together.
Those nations which live solely, or even chiefly, upon one or two kinds
of staple foods, such as rice, potatoes, corn-meal, or yams, do so
solely because they are too poor to afford other kinds of food, or too
lazy, or too uncivilized, to get them; and instead of being healthier
and longer-lived than civilized races, they are much more subject to
disease and live only about half as long.
THE THREE GREAT CLASSES OF FOOD-FUEL
Food is Fuel. Now what is the chief quality which makes one kind of
food preferable to another? As our body machine runs entirely upon the
energy or "strength" which it gets out of its food, _a good food must
have plenty of fuel value_; that is to say, it must be capable of
burning and giving off heat and steaming-power. Other things being
equal, the more it has of this fuel value, the more desirable and
valuable it will be as a food.
From this point of view, foods may be roughly classified, after the
fashion of the materials needed to build a fire in a grate or stove, as
Coal foods, Kindling foods, and Paper foods. Although coal, kindling,
and paper are of very different fuel values, they are all necessary to
start the fire in the grate and to keep it burning properly. Moreover,
any one of them would keep a fire going alone, after a fashion, provided
that you had a grate or furnace large enough to burn it in, and could
shovel it in fast enough; and the same is true, to a certain degree, of
the foods in the body.
How to Judge the Fuel Value of Foods. One of the best ways of roughly
determining whether a given food belongs in the Coal, the Kindling, or
the Paper class, is to take a handful or spoonful of it, dry it
thoroughly by some means,--evaporating, or driving off the water,--and
then throw what is left into a fire and see how it will burn. A piece of
beef, for instance, would shrink a good deal in drying; but about
one-third of it would be left, and this dried beef would burn quite
briskly and would last for some time in the fire. A piece of bread of
the same size would not shrink so much, but would lose about the same
proportion of its weight; and it also would burn with a clear, hot
flame, though not quite so long as the beef. A piece of fat of the same
size would shrink very little in drying and would burn with a bright,
hot flame, nearly twice as long as either the beef or the bread. These
would all be classed as Coal foods.
Then if we were to dry a slice of apple, it would shrink down into a
little leathery shaving; and this, when thrown into the fire, would burn
with a smudgy kind of flame, give off very little heat, and soon
smoulder away. A piece of raw potato of the same size would shrink even
more, but would give a hotter and cleaner flame. A leaf of cabbage, or a
piece of beet-root, or four or five large strawberries would shrivel
away in the drying almost to nothing and, if thoroughly dried, would
disappear in a flash when thrown on the fire. These, then, except the
potato, we should regard as Kindling foods.
But it would take a large handful of lettuce leaves, or a big cup of
beef-tea, or a good-sized bowl of soup, or a big cucumber, or a gallon
of tea or coffee, to leave sufficient solid remains when completely
dried, to make more than a flash when thrown into the fire. These, then,
are Paper foods, with little fuel value.