The leading principle in the use of food is that we should eat to live, but not live to eat. It is certain that more people die from eating too much than too little. It is wonderful to consider how little food animals, or human beings, can exist upon for a long time and remain in good health; and it is certain that the foundations of many diseases are laid by excessive eating. It must be borne in mind that the elaboration and assimilation of a large quantity of food requires the activity, or even hyperactivity, of several of our most important organs, upon the condition of which our length of life depends. And here we may repeat the statement that has been made so often in the course of this book, that overactivity of an organ may be followed by its exhaustion. By laying too great a burden upon an organ, and continually overworking it without giving it any rest for recuperation, we are burning the candle at both ends, and rapidly exhausting the vitality of such important organs as the liver, kidneys, pancreas, stomach, and intestines, not forgetting those important glands, the thyroid and parathyroid, which take a great share in the destruction of poisonous products formed in our bodies from the end-products of food.

We have just mentioned that with very little food animals, or human beings, can live for a long time. But prolonged underfeeding may be quite as dangerous as overfeeding. In starvation the resistance against infectious diseases, and especially tuberculosis, is diminished. This disease, the most common of all maladies, is found most often in underfed people, especially if they live in confined localities with little air and no sunshine. Moderation in food, as in everything else, is the only way to attain a happy old age.

The Romans had a very appropriate proverb which ran: “Omne quod est nimium, vertitur in vitium,” “Everything in excess becomes a vice.”

Much depends upon the quality of the food we take, for some foods are of very little nutritive value; and even of the most nutritive food, some parts may pass out as waste products, because those organs which elaborate and assimilate food may be partially, or wholly, changed by disease, and so unable to fulfill the work for which they are destined.

Therefore, given a moderate amount of food, the condition of the body and the maintenance of strength will depend mainly upon the nutritive value of that food. An exact method of estimating the nutritive value of food has been shown by Frankland, Stohmann, Danilewsky, and Rubner.

The best method of calculating the nutritive value of any food consists in estimating how many calories it produces in the body during combustion. One calorie is the amount of heat necessary to raise the temperature of one gramme of water one degree Centigrade. Comparing our system to an oven in which food represents the fuel: Just as oxygen is necessary for combustion in the oven, so we could not carry out the processes of combustion in our system without a plentiful supply of oxygen through our lungs and skin. Also, just as gases produced in a furnace must have free exit, so the carbonic acid, formed in our tissues in the processes of combustion, must be eliminated by the lungs and skin, otherwise auto-intoxication will occur. The above-named authorities have reckoned exactly how many calories the various kinds of food produce in our body.

All articles of diet can be classified into three principal groups: proteids, carbohydrates, and fats. According to the above-named authorities one gramme^[254] of proteid produces 4.1 calories; one gramme of carbohydrates, 4.1 calories; but one gramme of fat produces more than twice as many, i.e., 9.3 calories.

In order to maintain life without waste or without exposing ourselves to disease, it is necessary to use all three kinds of food; for although many animals, or human beings, can live for a certain time on only one variety of food, most of them would die if this were persisted in for a long time. The total exclusion of proteids especially would produce, after a certain time, a considerable wasting of the body tissues and certain death. According to Voith, it is necessary to take about 100 grammes of albumin a day if we want to avoid waste of body tissue. Proteid food cannot be replaced by either of the other two groups of food.

There are a series of facts which show that the estimate given by Voith is perhaps too high. Horace Fletcher has shown by experiments on himself, controlled by Professor Chittenden, that he could live in splendid health with food not containing more than 45 grammes albumin, and of 1600 calories heat value, in twenty-four hours, with a body weight of 186 pounds.

As shown by Professor Noorden,^[255] in Vienna, a man must take 30 to 34 calories for each kilo (2⅕ pounds) of his bodyweight when he is doing no work, and 34 to 40 calories with light, and 40 to 60 calories with harder work. Accordingly a man weighing 70 kilos would require to take food equivalent to about 2800 calories for light work, and about 3500 to 4000 calories for heavy work. But Fletcher got along well on 1600 calories with a body weight of 186 pounds. However, he lost some weight, 36 pounds, but became healthier and stronger than he was previously. Later on he still further reduced his diet and lived on 38 grammes of albumin and 1581 calories, continuing in perfect health.

By a series of experiments on a number of healthy American soldiers, continued for a long time, Chittenden^[256] and Horace Fletcher^[257] found that these men could do very hard work with an average of only 55 grammes albumin and 2700 calories; and, what is more interesting, their muscular power was doubled.

The same result was obtained by Professor Chittenden by experiments on seven of the finest athletes among the 2300 students of Yale University. He found the strength of these students increased as much as 48 per cent. One of them won the championship in gymnastics, open to all American universities, during the course of these experiments. Rechenberg found that the weavers of Zittau in Germany required 65 grammes of proteids a day.

Very interesting are the observations of Professor Baelz, of Tokio, made on the Japanese coolies, who drew the jinrickshaw containing Professor Baelz, who then weighed 160 pounds. These coolies took carbohydrates, mainly rice, with a proteid content of only 60 to 80 grammes. They were able to do their work exceedingly well on this meager diet. One day Professor Baelz gave them a little meat which they took for three days, and then refused it, saying they would take it after their journey was done. Baelz made the interesting observation that these men were able to go about 60 miles, drawing a man of 108 pounds, whereas Baelz, who followed riding in a carriage, had to change his horse six times and only beat them by half an hour.

The author of this book has observed that while taking 1½ liters of milk a day, 2 eggs, 40 grammes of butter, 3 rolls, 3 oranges, a pound of cherries, a cup of coffee with milk, and one tart, he was able to live very well for about two months without any loss in weight. The milk was of excellent quality, containing about 700 calories to the liter, and about 34 grammes albumin; thus he was taking about 70 grammes albumin and about 2300 calories a day, with a bodyweight of 155 pounds, and leading a very active life and he felt better than ever before.

Still we would not like to generalize and say that 55 or 60 grammes albumin in the day would be a suitable amount for every individual. Here, as everywhere, individuality and many other circumstances must be considered. What is good for one may not answer in the same way for another. The Japanese have constitutions different to the Europeans, for which reason we cannot apply to Europeans facts which hold good for Asiatics. Moreover, not everyone’s digestive organs are capable of utilizing ingested food to the same degree. The quality of the food is also of great importance, and likewise its digestibility. Therefore the question is very complex, and, for these and other reasons, the discussion of which would lead us too far, we cannot recommend a diet containing such a small amount of albumin for general use.

Everybody likes to judge from his own experience, and so the author is inclined to the belief that, when milk is taken in large quantities, in addition to fats and carbohydrates, it is possible to get along with a smaller amount of albumin, and of calories in general. Milk, in healthy stomachs and intestines, is very easily absorbed, and the food leaves less residue than most other kinds of food. Then, again, milk contains in a wonderful combination all the three main groups of food. So we believe that when milk is taken as the main article of diet we can get along with a smaller number of calories, without any prejudice to our health.

According to Rubner^[258] the following number of calories are indicated daily:—

Albuminous food serves, according to the prevalent opinion, to build up our body tissues, carbohydrates to produce the energy that is necessary for muscular work, and the fats to produce heat.

Accordingly, persons who are growing will need more albumin in order to produce body tissues; and albuminous food will be indicated for those who have had much loss of tissue, as in convalescence after wasting disease. By albuminous food the waste of body tissues can best be replaced. Also after different kinds of excesses where tissue is wasted (e.g., after sexual excesses) albuminous food will be indicated.

Such a food is also necessary for women during pregnancies, and especially during lactation.

In any of these conditions the minimum of albuminous food, taken daily, should certainly be 100 grammes. But other persons can often manage with less without any wasting of the body proteids, so long as carbohydrates and fats are taken simultaneously in sufficient quantities.

Besides the three principal groups of food there are certain other kinds which are almost as indispensable, e.g., mineral matter and water, without which no animal or man could live, and vegetable acids and cellulose.

The most important mineral matters are lime salts, mainly in the form of phosphates. They are present in greatest amounts in cows’ milk. Common salt is a most important element of food, for which animals and men often risk their life. As Bunge shows, where vegetables that contain much potassium are taken, then common salt must be taken as well. He has shown by experiment upon himself, that when potassium salts are taken a great quantity of sodium chloride is eliminated from the body. The reason is, that when a potassium salt is taken, e.g., carbonate of potassium, and this, in the blood, meets with chloride of sodium, then chloride of potassium and carbonate of sodium are formed. But the kidney’s duty is to see that the composition of the blood is maintained, and that foreign substances, or the surplus of a normal substance like carbonate of sodium, are eliminated. Hence the carbonate of sodium and the chloride of potassium are together eliminated, and thus our blood loses two important elements: chlorine and sodium. Thus, when potassium is taken, the body loses sodium chloride, and then more of this substance is required.

A diet of potatoes necessitates much salt, as they are rich in potassium; on the other hand, rice contains only minimal quantities of potash. Potatoes contain 42 grammes of potassium in 100 grammes; rice only 1 gramme. Thus rice as food would require only the smallest amount of salt.

At the same time Bunge points out the great dangers to the kidneys of a diet from which quantities of an alkali salt are formed and circulate through these organs. We can draw a practical conclusion of great value from Bunge’s observations, and not use much salt in our food, nor too large quantities of vegetables containing much potassium, if we want to save our kidneys from harm. That salt is deleterious to the kidneys, especially when previously damaged, is shown by the works of Achard and Loeper,^[259] Strauss,^[260] Vidal and Javal,^[261] and others. We have enlarged upon this in our chapters on the functions of the kidneys and their hygiene.

A mineral of great importance is iron, which is contained in pig’s blood to the largest extent, and in certain vegetables and fruit in considerable quantities. Vegetables and fruit are also rich in vegetable acids, and also contain a large amount of cellulose, which plays an important rôle in the normal evacuation of the bowels, being the most natural stimulus for this purpose.

Condiments are also indispensable in a certain quantity with our food, for without them the food would have no taste and would not stimulate appetite, which is of great importance for digestion. On the other hand, too much of these condiments would irritate vital organs, like the stomach, intestines, liver, kidneys, etc. Therefore they should only be used in moderation, and the more potent ones, like mustard and pepper, should be avoided, or only taken in minimal quantities. Vinegar would not be so bad if it did not so often contain sulphuric acid. Certain sharp sauces which are much used are veritable poisons to the kidneys. This is true of soup that contains them, and even strong bouillon, when it is taken every day in large quantities, may be injurious to the kidneys and affect unfavorably the blood pressure since it contains many meat extracts. To minimize the dangers of all these kinds of harmful materials, and also of the end-products of nitrogenous food when passing through the kidneys, it is best and healthiest to drink large quantities of water, hard water being most desirable, according to Roese, because of its richness in lime salts. It is advisable to drink this after meals; but if water is not taken in too large quantities it may be perfectly harmless to take it during meals. It helps the appetite in many persons, and encourages the absorption of the food. If taken in too large quantities it may dilute the gastric juice, although in such a case the glands of the stomach strive to keep up the standard acidity, and secrete more acid in consequence. As shown previously, a certain degree of fluidity of the intestinal contents is indispensable for the healthy action of the bowels. For all these reasons we recommend a moderate amount of good fresh water daily. Happily, most of our foodstuffs, especially green vegetables and fruit, contain water in large quantities.

Under the name stimulants we include various kinds of food accessories. The most important of these are alcoholic drinks. It has been shown by physiologic experiments that when alcohol is taken in moderate quantities it is harmless, and at the same time may be of value as a nutrient foodstuff. It is evident from the result of the experiments of Atwater and Benedict that alcohol has a nutritive value, and that as a kind of fuel it can largely replace carbohydrates and fats. In such quantities it also stimulates digestion and other functions, e.g., those of the heart and nervous system. Such small quantities of alcohol are contained in beer and wine. According to Rubner, 100 parts of beer contain:—

English and American beers, however, are much stronger in alcohol; thus Scotch ale contains 8.50 per cent. of alcohol; London porter, 6.90 per cent.; lager beer, 3.90 per cent.

Beer is also of nutritive value on account of its sugar and dextrine, which are in considerable amount, especially in dark beers; it also contains an appreciable amount of albumin. On the other hand, beer has the disadvantage of forming uric acid in considerable quantities, as shown by Walker Hall and Haig. Beer also conduces to obesity. There can, however, be no harm in taking a small amount of light beer every day.

Wine contains proteid substances, carbohydrates, and salts. In some kinds of wine, like port, sherry, Tokayer, Malaga, and Madeira, there are large quantities of sugar. The alcohol contents of the different kinds of wine are given by Rubner as follows:—

Thus, Tyrolean wines are the lightest, French wines come next, but Mosel wines are the strongest, in spite of the popular belief that they contain only little alcohol.

Wines contain more acids than beer (0.41 per cent. to 0.69 per cent., according to Rubner), whereas beer has only 0.1 per cent. As wine contains vegetable acids, just as do vegetables and fruit, they may be of a certain dietetic value on this account.

We do not think it harmful if old people drink, every day, a few glasses of good French claret, although we are not prepared to indorse the dictum of Hufeland that wine is the milk of the old. Much greater precaution must be taken in the enjoyment of spirits: brandy (cognac), whiskey, and rum. These beverages contains 50 to 60 per cent. of alcohol. Still we do not think that small amounts of whiskey, if taken occasionally and in measured quantities, can be dangerous. Care must be taken to get whiskey of good quality. There can be no doubt, however, that when large quantities are taken, as in dipsomania, old age is brought on sooner. It is claimed that after taking whiskey less uric acid is eliminated than after taking the other alcoholic beverages, as beer or some kinds of wine.

Coffee, tea, and cocoa also belong to the class of stimulants, and we will treat of them in a special chapter, as also of tobacco.

Great moderation must be observed in the amount of food we take daily. Too rich food would induce not only diseases of the digestive organs, but also disorders of metabolism, like obesity, gout, or diabetes, and thus shorten life. Arteriosclerosis is also promoted by such a diet.

The more food also the more exercise should be taken, and the more we work the more food should we take.

Aged persons should take less proteid food and more carbohydrates. Proteid food is better suited to young persons who are growing. Besides carbohydrates, milk is also especially indicated for old persons, as are also certain amounts of fat, butter, etc.

The amount of food should also depend upon the climate; thus, in winter more fat should be taken, for fat produces heat. Inhabitants of northern climes eat much fat, and in Scandinavia more butter is taken than in southern countries. In hot summer weather little proteid food is required, and carbohydrates, vegetables, and fruit are more suitable.

Much depends on the preparation of food. In the process of cooking the food should be brought into the most advantageous form for absorption and assimilation. Therefore much depends upon the way in which the food is cooked, and the great importance of this fact is shown by the establishing of courses in cooking in Berlin under the direction of Prof. H. Strauss.

In the choice of food attention must be paid to its digestibility. A robust man, who works hard and takes much exercise, can digest easily the most indigestible vegetable food, whereas a man occupied with scientific work and sitting down all day will have a greater difficulty in digesting it. Aged persons, whose digestive glands are atrophied, are unable to digest food which presents great difficulties to the action of their juices. Therefore raw milk, whipped eggs, tripe, lamb, rice, sago, tapioca, barley, and soft boiled eggs, are the most digestible foods for them. Of the vegetables, rice is among the easiest to digest, and it will also soonest disappear from the stomach. There are special preparations made from various kinds of cereals, finely ground, and containing the most nourishing elements, and these may be advisable for aged persons. There are also albuminous foodstuffs in which the albumin is changed into the form of peptones. However, it has been shown by Professor Ewald that they contain very little peptone, but mainly albumose, its precursor. Others of these foodstuffs have the starch transformed into dextrin or maltose. There can be no doubt that aged persons will thrive and prosper on the best of these preparations, which also have the advantage that they can be taken in conjunction with milk. Another point in their favor is that they require little mastication.

We add here a table after Professor Ewald, of Berlin, on the digestibility of the various kinds of food:—

The digestibility of these various kinds of food is calculated for the normal stomach. By following the above table we can make the best choice of easily digestible food. Especially for aged persons we should choose such, and at the same time we should mince them, or give them in the form of porridge, which is still better. We must do this because aged persons do not possess, as a rule, good teeth, if any, and thus cannot fulfill the demands of mastication, which we will treat of later on in a separate chapter.

The food should not be too hot nor too cold, as, if it is, the stomach, and even intestines may be damaged; on the other hand, as a rule, warm food disappears sooner from the stomach; but there are many exceptions to this rule.

The keynote in the hygiene of food is moderation. We should never eat more than necessary to satisfy hunger. Most people know when they have had enough; and as a rule animals never eat more than enough to satisfy them, and then they will refuse more food. But with the intelligent human being it is different, and there are not a few who eat more than they require, and thus dig their graves with their teeth. Moderation is all important; it is, indeed, the cause of longevity of those persons who live about 100 years.

We know the story of Cornaro, who became ill at 40 through immoderate living. He recovered his health by reducing his food to the necessary amount only, and then lived, happy and healthy, to 100 years. Mr. Horace Fletcher,^[262] and many other persons, have recovered their health through moderation in food, after having come to the brink of death through immoderation. Such examples we may often see, and they are eloquent advocates of moderation in diet.

We will show later that we can only digest food that we eat with relish; therefore never let us be persuaded to partake of food, or compel ourselves to eat, when we are not hungry. Therefore, at least six hours should pass between dinner and supper, and five hours between breakfast and dinner. It is more healthy, and especially conducive to healthy sleep, to have dinner at 12 or 1, and supper at 6 or 7. Meat should only be taken once a day, at dinner, and in the evening much less should be eaten than at noon. Meat should never be taken for breakfast. We would recommend the following diet:—

BREAKFAST.

Grape fruit or oranges, 2 eggs (soft boiled), cereals, stewed fruit, white or brown bread, fresh butter, a teaspoonful of marmalade or other kind of jam, fresh cherries, or fresh strawberries, or other fruit in season, especially grapes, half to one pint of milk.

DINNER.

Soup, fish or meat, vegetables, stewed fruit, fresh fruit, white or brown bread.

Like breakfast: one pint of milk, or half a pint of sour milk, kefir, or koumiss. Also, if liked, sour milk during the day.

In the above diet list we have a variety of foods, which variety is of great importance.

It is very advantageous, according to our observation, to append to this diet some milk, carbohydrates, fat, green vegetables, and fruit, with the exclusion of meat. This we may do, especially if the weather is warm in spring, summer, or early autumn; but in winter the above diet with meat should be taken. It would be an excellent thing to take these two diets in alternating periods. Much will depend upon the tastes of each person, and the special indications which we give later on in their respective chapters.

When no meat is eaten, then at least 1½ to 2 liters of rich milk should be taken, and some cream cheese.

After these general remarks on food we will treat of the merits and drawbacks of the various kinds of food.