The Digestibility of Fats. We have now come to the last group of the real Coal foods, namely, the fats. Fats are the "hottest" and most concentrated fuel that we possess, and might be described as the "anthracites," or "hard coals" of our Coal foods. They are, also, as might be expected from their "strength" or concentration, among the slowest to digest of all our foods, so that, as a rule, we can eat them only in very moderate amounts, seldom exceeding one-tenth to one-sixth of our total food-fuel. It is not, however, quite correct to say that fats are hard to digest, because, although from their solid, oily character, they take a longer time to become digested and absorbed by the body than most other foods, yet they are as perfectly and as completely digested, with the healthy person, as any other kind of food. Indeed, it is this slowness of digestion which gives them their well-known staying-power as a food.

Their Place in our Diet. The wholesomeness of fats is well shown by our appetite for them, which is very keen for small amounts of them—witness, for instance, how quickly we notice and how keenly we object to the absence of butter on our bread or potatoes. To have our "bread well-buttered" is a well known expression for comfort and good fortune; yet a very little excess will turn our enjoyment into disgust. Fat, and particularly the cold fat of meat, "gags" us if we try to eat too much of it.

Fortunately, most of these fat-foods are quite expensive, pound for pound, and hence we are not often tempted to eat them in excess. Within proper limits, then, fats are an exceedingly important and useful food—a valuable member of the great family of Coal foods.

The Advantages of Fat as a Ration. The high fuel value and the small bulk of fats give them a very great practical advantage whenever supplies of food have to be carried for long distances, or for considerable lengths of time, as in sea voyages and hunting and exploring trips. So that in provisioning ships for a long voyage, or fitting out an expedition for the Arctic regions, fats, in the shape of bacon or pork, pemmican,[9] or the richer dried fishes, like salmon, mackerel, and herring, will be found to play an important part. Fats also have the great advantage, like the starches, of keeping well for long periods, especially after they have been melted and sterilized by boiling, or "rendering," as in the case of lard, or have had moderate amounts of salt added to them, as in butter.

If you were obliged to pick out a ration which would keep you alive, give you working power, and fit into the smallest possible bulk, you would take a protein, a sugar, and a fat in about equal amounts. Indeed, the German emergency field-ration, intended to keep soldiers in the field for three or four days without their baggage-wagons, or cook-trains, is made up of bacon, pea-meal, and chocolate. A small packet of these, which weighs only a little over two pounds, and which can be slipped into the knapsack, will, with plenty of water, keep a soldier in fighting trim for three days.

Butter. The most useful and wholesome single fat is the one which is in greatest demand—butter. This, as we have seen, is the churned and concentrated fat of milk, to which a little salt has been added to keep the milk-acid (lactic acid) which cannot be entirely washed out of it, from "turning it sour" or rancid. The rancid, offensive taste of bad or "strong" butter is due to the formation of another acid call butyric ("buttery") acid.

Butter is the best and most wholesome of our common fats because it is most easily digested, most readily absorbed, and least likely to give rise to this butyric acid fermentation. We should be particularly careful, even more so almost than with other foods, to see that it is perfectly sweet and good, because when we swallow rancid butter, we are simply swallowing a ready-made attack of indigestion. Most people's stomachs are strong enough to deal with small amounts of rancid butter without discomfort; but it is a strain on them that ought to be avoided, especially when good butter is simply a matter of strict cleanliness and care in handling and churning the cream, and of keeping the butter cool after it has been made.

Plenty of sweet butter is one of the most important and necessary elements in our diet, especially in childhood. And if children are allowed to eat pretty nearly as much as they want of it on their bread or potatoes, and plenty of its liquid form, cream, on their berries and puddings, it will save the necessity of many a dose of cod-liver oil, or bitter physic. Cream is far superior to either cod-liver or castor oil for keeping us in health.

Oleomargarine. On account of the expensiveness of butter, there are a number of substitutes sold, which go under the name of oleomargarine. These are made of the fat, or suet, of beef or mutton, mixed with a certain amount of cream and real butter, to give them an agreeable flavor. They are wholesome and useful fats, and for cooking purposes may very largely be substituted for butter. Owing to the fact that their fat is freer from the milk acids, they keep better than butter; and sweet, sound oleomargarine is to be preferred to rank, rancid butter. But it is not so readily digestible as butter is; is more liable to give rise to the butyric acid fermentations in the stomach; is not nearly so appetizing; and its sale as, and under the name of, butter is a fraud which the law rightly forbids and punishes.

Lard. The next most useful and generally used pure fat is lard—the rendered, or boiled-down, fat of pork. It is a useful substitute for butter in cooking, where butter is scarce. But, even in pastry or cakes, it has neither the flavor nor the digestibility of butter, and the latter should always be used when it can be had.

Bacon and Ham. The most useful and digestible fat meats are bacon and ham, as the dried, salted, and usually smoked, meat of the pig is called. Like all other fats, they can be eaten only in moderate amounts; but thus eaten, they are both appetizing, digestible, and very nutritious. One good slice of breakfast bacon, for instance, contains as much fuel value as two large saucers of mush or breakfast food, or two eggs, or two large slices of bread, or three oranges, or two small glasses of milk, or a quart of berries.

NUTS

How Nuts should be Used. Another form of fat is the "meat" of different nuts—walnuts, pecans, almonds, etc. These are quite rich in fats, and also contain a fair amount of proteins, and are, in small quantities, like other fats, appetizing and useful articles of food. But they should not be depended upon to furnish more than a small amount of the whole food supply, or even of its necessary fat, because nearly all nuts contain pungent or bitter aromatic oils and ferments, which give them their flavors, but which are likely to upset the digestion. This is particularly true of the peanut, which is not a true nut at all, but is, as its name indicates, a kind of pea grown underground. Peanuts, on account of their large amount of these irritating substances, are among the most indigestible and undesirable articles of diet in common use. A certain amount of these irritating substances present in nuts may be destroyed by careful roasting and salting; but this must be most carefully done, and it shrinks them in bulk so that the finished product is far more expensive than butter or fat meat of the same nutritive value. Good salted almonds, for instance, cost fifty to eighty cents a pound.

The proper place for nuts is where they usually come on our tables—at the end of a meal. Those who attempt to cure themselves of dyspepsia by a nut diet are simply making permanent their disease.