Practical observations upon the chemistry of food and dietetics

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Introduction

There has probably never been a time when the attention of the public has been more generally directed toward the care of the health than the present. Bvery newspaper in the land seems to have a column or a corner devoted to the development of the body, to the care of the skin, to the obliteration of wrinkles, to the attainment of beauty, or to some phase of the care of the body.

Magazines devoted to physical culture, to diet, to vegetarianism, etc., are widely circulated and read; there are books devoted to the thesis that fruit acids are deleterious and poisonous, and other books to prove that they are indispensable. Pseudo-scientific articles attempting to show that potatoes produce large abdomens, that tea causes the teeth to protrude, that carbohydrates have the effect of overdeveloping the chin, that onions relax the jaw tissues, and a host of like absurdities, have appeared in popular magazines. Books have been written which try to prove that all our ills come from uric acid foods, and many essays and pamphlets to show that that proposition was not true.

Then there are raw-food people and vegetarians and partial vegetarians and nutarians and fruitarians ; also b INTRODUCTION.

there are grape cures and apple cures and milk cures and hunger cures and thirst cures. The stores are full of malted foods and steamed foods and digested foods and concentrated foods and health foods, and finally, after seventeen years of unrighteous opposition on the floor of the United States Senate, the Pure Food Bill has passed.

All of which goes to show that the popular mind has been awakened and directed, however mistakenly, toward the subject of the care of the body. As is often the case, the medical profession is lagging in the rear. Nothing corresponding to the popular interest in the subject has been awakened in the professional mind. There is probably no subject connected with the care of patients that doctors are so perplexed by as diet. Many physicians have their ideas of diet based purely on prejudice; what happens to agree with them personally they recommend to their pa" tients, and what disagrees with their particular organism they sternly forbid. The questions most frequently propounded to doctors by patients probably relate to the diet, and the most confusing and inaccurate directions that patients receive from doctors relate to the same important subject. A knowledge of the principles common to all foods, and the function of each, is indispensable to a physician. A knowledge of the proportion of these constituents in many of the standard foods should follow, and would

INTRODUCTION. 7

be found of the greatest advantage in practice. A knowledge of the general principles of cooking is also extremely useful.

These considerations, together with the fact that the branch of dietetics which relates to standard dietaries has very recently undergone changes so great that they are little short of revolutionary, seem to indicate that a concise book upon the subject embodying the latest views might be welcome.

J. B. S. King, M. D.

CHEMISTRY OF FOOD AND DIETETICS.

GENERAL PRINCIPLES OF NUTRITION.

CHEMICAL CONSTITUENTS OF FOOD.

Human food in the complex must contain all the elements of the human body. The elements of the human body are as follows:

Carbon, hydrogen, oxygen, nitrogen (gaseous).

Potassium, sodium, calcium, magnesium (mineral and basic).

Phosphorus, sulphur, ^chlorine, iodine (mineral and acidulous).

Silicon, iron (mineral and metallic).

Traces of other elements, such as arsenic and copper, are found in minute quantities, but the above are all that are of practical interest so far as the study of nutrition goes.

None of the above elements exist in a free state, either in food or in the body ; they are all chemically combined to form certain compounds, and it is these compounds that are to be studied as the principles of food. The first of these is

* Chlorine, although a gas, is here classed with acidulous minerals on account of its analogy to iodine.

Water. — Composed of the elements hydrogen and oxygen of the above list ; it is the universal medium, diluent and solvent, found in all foods and indispensable to life. It is not decomposed in the body, and hence furnishes no energy ; various foods contain from 10 to 95 and the human body 70 per cent, of it.

Mineral Matters. — These are alkaline and earthy salts ; they consist of calcium, magnesium, potassium and sodium, combined with sulphuric and phosphoric acids to form sulphates and phosphates, and with chlorine to form chlorides. Phosphorus, sulphur and iodine also exist and perform important functions, in combination with organic albumins. Sodium chloride is found in larger proportion in the serum of the blood, potassium chloride in the red blood corpuscles and in muscle cells, potassium phosphate in the brain and nerve tissue; calcium, magnesium and silicon in the cartilages, bones and teeth ; iodine in the glands, and iron in the red corpuscles.

Five per cent, of the whole body or about seven and a half pounds in a man of average size consists of mineral matters, five-sixths of which is in the osseous framework. These minerals are absolutely essential to life, and even if all the other constituents of food are furnished, death occurs after about one month of their deprivation. The daily intake and output of mineral matter is about 400 grains, something less than an ounce, and would be fully supplied by ordinary food, even without the extra additions of common salt that the cook usually adds.

The most important minerals are lime, soda, iron and phosphoric acid. Phosphorus plays an important

GENERAL PRINCIPLES OF NUTRITION. 11

role in nutrition; in addition to its usefulness in building- the bony tissues, it is an essential of cell activity. Next to bones, the brain and nerves are rich in phosphorus. Strange to say, the ligaments and tendons, whose function is so similar to bones, contain the least phosphorus of any animal tissue. The daily need of iron is very small, only about onesixth of a grain, and that amount is easily contained in ordinary food.

Protein. — Nitrogen is the characteristic element of this class. It includes the most essential as well as the most worthless of foods. The American Association of Agricultural Colleges and Experiment Stations adopted and recommended the term protein, in place of proteid, albumin, albuminoids, nitrogenous foods, etc., employed by various writers, and this name is here used.

Protein may be divided into three classes, albuminoids, gelatinoids and extractives. (Note I.)

Albuminoids include the white of egg, the lean of meat, the casein of milk and the gluten of wheat. These are indispensable ; life cannot be maintained without them. They build up new tissue during the period of growth ; they repair the waste of tissue in adult life and, by virtue of the carbon and hydrogen that they contain, they also contribute to the heat and energy of the body.

Gelatinoids occupy a very secondary position, for the reason that their nitrogen is not available for the repair of tissue, as is that of the albuminoids; they save the latter from being consumed, however, and leave it intact to perform its tissue-building function instead of being used up in energy ; hence they are sometimes called albumin-sparers. Gelatin is a familiar example of this class ; glue is an impure form of it.

Extractives come under this head only because they contain nitrogen; they furnish scarcely any strength to the body and are very hard to eliminate, being potent producers of uric acid. They serve as stimulants and appetizers. The agreeable savor of cooked meats is largely due to extractives, and they form the principal part of the commercial meat extracts.

Carbohydrates. — Consist of carbon, hydrogen and oxygen. They are almost exclusively of vegetable origin, the only animal carbohydrates being milk-sugar and honey.

They are the chief fuel of the body, furnishing it with muscular energy and figuring largely in the production of animal heat. They are represented by starches, sugar, pectins and gums.

Hydrocarbons. — These are fats and oils of all kinds, both from the vegetable and animal kingdoms. They consist of the same elements as the carbohydrates, but in a very different relative proportion. They are the most powerful heat producers of all, and hence are particularly adapted to cold weather and cold climates.

The above facts are shown in a summary in the following table :

THE FUNCTIONS OF FOOD.

CONSTITUENTS OF FOOD IN GENERAL.

Minerals Earthy and Alkaline Salts.

Hydrocarbons Fats and Oils.

Carbohydrates Starches, Sugars,

Gums.

Protein Meat, Fish, Eggs,

Peas, Grains, Beans, Cheese, Gelatine.

Hydrogen and Oxy- The universal gen. diluent and

solvent.

Necessary to osmosis, and assimilation; maintain the alkalinereaction of the tissues.

Heat and Energy.

Calcium, Magnesium, Sodium, Potassium, Phosphorus, Chlorine, Sulphur, Iron, and Silicon.

Carbon, Hydrogen, Oxygen.

Carbon, Hydrogen, Oxygen.

Nitrogen, Carbon, Hydrogen, Oxygen.

Energy Heat.

and

Tissue builders and repairers. Energy and Heat.

THE FUNCTIONS OF FOOD.

It may be seen from the foregoing table that food has a threefold function: First, it must supply animal heat ; second, it must supply energy for work ; third, it must furnish the elements for growth and for the replacing of worn-out tissue.

Animal heat is supplied by all the foods in varying degrees; in the highest degree by fats and oils; in a considerable degree by sugars and starches ; protein also is capable of maintaining animal heat.

Energy for work is furnished largely by the starches and sugars, in a less degree by the fats and oils. Protein is also capable of furnishing energy with great rapidity.

The building and repair of tissue is the peculiar function of protein. It will be noticed that protein alone is capable of fulfilling all the functions of food, and this universality of use gives it its great prominonce. Instances can be cited where men have lived for long periods of time with a high degree of vigor and well-being upon nothing but water, meat and salt. Such a highly nitrogenous diet, however, requires an active life in the open air, and even then should not be maintained indefinitely.

For reasons hereafter stated it seems desirable that the protein consumption should not be much in excess of the amount required to make good the tissue waste, and that most of the requisite heat and energy of the body should be derived from the carbohydrates and fat, rather than from protein.

The comparison of the human body to a steam engine is so old that, when used now, it is generally with an apology for its triteness. It is, notwithstanding, a very useful and apt illustration of many things about nutrition. Thus the protein that maintains the integrity of the tissues may be compared to the steel and iron that replace old and worn-ont parts and keep the engine in repair.

The carbonaceous food that supplies animal heat and the ability to do work is like the coal that makes the steam pressure. The comparison may easily be extended with advantage to the subject of excreta.

The burning of coal under the boiler and the digestion of food in the bodv are essentially alike in that they are processes of oxidation or combustion, the inevitable result of which is waste products or ashes.

If the coal is of good quality and in proper quantity, the ash is hue and completely burned. If of

STANDARD OF VALUE. 15

poor quality or in too large quantity, clinkers and incompletely consumed cinders are the result. If the draft is slow or the supply of air deficient, cinders are again in evidence.

Normal urine and feces represent the fine, wellburned ash of good coal. Uric acid crystals, amorphous urates and phosphatic sediments in the body or urine, from overeating or from improper food, correspond to the clinkers and half-burned cinders from bad coal or too much fuel that clog the fire. When resulting from insufficient exercise or scanty intake of oxygen, as in the damaged lungs of a consumptive, they represent the same thing, but then occurring from choked draft.

The smoke and vapors that escape through the chimney represent the expired air and the gaseous waste of the system. An important difference is that the human engine builds its own parts, repairs its own breaks, oils its own joints, frees its own pipes and keeps up its own fires, with an economy and perfection that the best mechanism of man only clumsily and inadequately imitates. (Note II.)

STANDARD OF VALUE.

One of the inherent difficulties of the subject of diet has been to fix some standard by which the relative nutritive value of food might be measured. Of late years a standard of value has been adopted, called the Calorie, which allows of a much more accurate comparison of various foods than was formerly possible. It is based upon the fact that the digestion of food is essentially the combustion of food, and the amount of heat evolved by the complete combustion of a certain amount of food has been found to be the best index of its nutritive value that we have.

The amount of food used in the experiment is one gram (15 j4 grains).

The standard of heat production is called a Calorie, written with a capital, and means the amount of heat required to raise one liter of water one degree Centigrade (or one pound of water four degrees Fahr.). To ascertain the value of any food by this standard one has to find out how many degrees Centigrade one liter of water is raised by the complete combustion of one gram of the food in question. The result gives the value of the food in terms of Calories. It is freely admitted that combustion outside the body and digestion within it are not strictly convertible terms, especially in regard to protein, yet even with this admission, it has been found that no other method of comparison gives such an accurate idea of food values. The fuel value of one gram of each of the three important constituents of food, according to the most recent experiments, made by Atwater, is as follows : (Note III.)

Protein 4 Calories.

To apply the Calorie standard to any food it is only necessary to know its chemical composition, and then to multiply the percentage of protein and carbohydrate by four and the percentage of fat by 9.1. The result gives the number of Calories afforded by 100 grams of the food.

STANDARD OF VALUE. 17

For example : Eggs contain, according to the average of sixty analyses, 14.8 per cent, of protein, 10.5 per cent, of fat and no carbohydrate to speak of. Then

154.7

Therefore, the value of 100 grams of eggs (two average sized eggs) is 154.7 Calories.

If a sample of milk contains 4 per cent, of protein, 5 per cent, of sugar and 4 per cent, of fat ; then the Calorie value of 100 grams (3 1-3 ounces) would be

The usefulness of the Calorie standard is very great, but it should not be overestimated nor considered as more than one factor, though an important one, in the comparison of foods. Base of digestion, rapidity of digestion, completeness of absorption and cost must all be considered in putting a definite value upon an article of diet. Sawdust, for instance, would give at least as high a Calorie value as starch, but owing to its indigestibility is of no nutritional value whatever.

In order to give an idea of the fuel value of some common foods, the number of Calories yielded by 100 grams is given in the following table. One hundred grams (3 1-3 ounces) would not be far ffom the amount of edible substance in an ordinary helping of meat, eggs or potato at a meal.

ioo grams (3 1-3 oz.) medium fat pork . . 285

" bacon 620

" beef 170

cheese 411

oats 396

wheat 339 white bread 263

johnny cake 248

milk 72 potato 66

The Calorie value of the food for twenty-four hours of a man of average weight should be from 1,500 to 3,000. The lower number for a sedentary life, the higher when engaged in active labor.

ABSORBABILITY OF FOOD.

In estimating food values the question of the ease and completeness of its absorption becomes an important factor. The carbohydrates (starch and sugar) of all kinds of food seem to be absorbed to the last particle; cellulose, although of the same percentage composition as starch, is not absorbed at all, yet counts equally in estimating Calorie values. Of all this class, fruit sugar (glucoses) enters most rapidly into the blood, cane sugar (saccharoses) next and starch (amyloses) the least rapidly.

Fat is very completely absorbed, but not with great rapidity^ the ease with which various fats are absorbed depends largely upon their melting point ; the

ABSORBABILITY OF FOOD. 19

lower the melting point the more readily it yields to the digestive organs, and vice versa.

Protein from animal sources is more readily and completely absorbed than that from the vegetable kingdom. The completeness of protein absorption depends npon its relative amount ; when the per cent, is small there is a greater waste than when the amount is greater. This is probably dne to its entanglement in the larger proportion of cellulose and starch present, so that it escapes the direct action of the digestive juices.

The protein of meat and eggs, for instance, is completely and easily absorbed, less than 3 per cent, being wasted, while the protein of peas is wasted to the extent of 10 per cent., and that of potatoes to the extent of about one-third. Vegetable food, in general, shows a much greater loss of protein than do meat and eggs. When we come to consider the absorption of the whole food, however, which is a fairer point of view, we find that, so far as the important vegetable foods go, they exceed meat as a whole. Thus, of w T hite bread only 4 per cent, is wasted, while of the whole meat (not protein alone) about 5 per cent, is lost. Fine white bread is absorbed more completely and yields more heat and energy than the coarse breads. This is contrary to the statements made by many food journals and even by works on the subject, but is nevertheless correct. The point was proved by experiments made in the laboratory of the University of Minnesota in 1890. (Note IV.)

The coarser breads, however, contain more of the various constituents of the grain and are a better food for growing children and for those leading sedentary lives.

ELIMINATION.

There is no fire without ashes, and the fire of life is no exception to the rule. The insoluble debris of food, the waste products of combustion and the detritus from the decay of tissue, all produce a quantity of effete matter that must be gotten rid of, in order that the body may be in a clean and healthy condition.

The waste and useless end-products of combustion in the body issue forth in various ways, through organic pipes and tubes, which may be compared to the sewers of a city ; the carbon appears as carbon dioxide in the expired air from the lungs, and as carbonates of the alkalies and alkaline earths in the urine and perspiration.

Hydrogen escapes as water by the same routes. Phosphorus, sulphur and chlorine unite with oxygen, forming acids, which, in turn, combine with the alkalies and earths to form soluble salts, which appear in the urine.

The greater part of the nitrogen (85 per cent.) appears in the urine as urea, a soluble neutral crystalline body ; a part also appears as a hard, gritty, insoluble, crystalline, bi-basic acid, known as uric acid.

Between the food as it enters the mouth and its ultimate waste products that leave the body there is a multitude of intermediates concerning which we are far from possessing complete knowledge.

This much is known : The products of carbon met-

ELIMINATION. 21

abolism, consisting, as they do, of carbon dioxide and water, are comparatively easy for the eliminative organs to handle. Owing to their fluid and gaseous nature they are not capable of seriously encumbering the system. The worst thing that they can do is to produce an excessive formation of fat, which, while not desirable, is not in itself poisonous. The same innocuousness does not go with the products of nitrogenous metabolism. These form a series of hard, more or less insoluble, crystalline bodies that are passed along from tissue to tissue and from organ to organ with difficulty, and are prone to encumber and obstruct the organs through which they must pass and also to fret and injure their structure.

Nor is it mere mechanical obstruction that characterizes them ; most, if not all, of these tissue-fretting bodies exert a positive toxic action upon the system. Xanthin, hypoxanthin, creatin, creatinin, adenin, ammonium carbamate, urea and uric acid are some of the principles that are known to exert a poisonous influence when present in the body in slight excess.

All flesh foods contain these substances ; they are also formed to a slight extent in our own tissues and from the digestion of vegetable protein. Such facts as we possess make it clear that excess of protein, especially of animal origin, is more harmful to health than excess of carbohydrates or fat. The many varieties of gout and innumerable obscure diseased states have their roots in this nitrogenous debris-encumbered condition of the system.

Thorough elimination means clean tissues, and clean tissues mean vigor, flexibility and endurance.

It is evident from the foregoing considerations that nitrogenous foods clog the system more than others, and it is an obvious inference that too much of that kind of food is especially to be avoided. Attention and appreciation of these facts should impress upon the mind the importance of avoiding all excessive ingestion of food. It is by ingestion that elimination may be controlled, and the regulation of the intake of food is the only proper and orderly way to control it.

It is most unfortunate that the public has been educated to regard catharsis as the key to proper elimination. The effects of overindulgence, gluttony and improper foods are supposed to be promptly relieved by a cathartic pill, and this unscientific delusion is fostered by numerous patent medicine advertisements in the daily press. The profession should endeavor to teach the laity that the evacuation of the bowels is the last and outermost of a long series of internal purifications, and that to force them to overaction is to begin purification at the wrong end. It is certainly a very inadequate corrective of improper eating.

THE DAILY AMOUNT OF FOOD.

As the result of many years' observation and experiment, certain amounts of each of the three chief food principles have been set down as necessary for the preservation of health and strength. The necessary data were obtained by the so-called empirical method, that is, by observations made upon healthy individuals eating as much as they wanted of what

THE DAILY AMOUNT OF FOOD. 23

they pleased. The food consumed was analyzed and the amounts of protein, carbohydrate and fat determined. The excreta during the same period were also analyzed, so as to show whether the income of food and the outgo, as represented by the excreta, were balanced or in equilibrium.

The quantities thus obtained by various observers, acting independently, were in fairly close agreement with each other and averaged about as follows :

Protein, 120 gm. (4 oz.) ; fat, 59 gm. (2 oz.); carbohydrate, 500 gm. (17 oz.).

It should be understood that these figures refer to dry material and not to food in its ordinary condition. Translated into quantities of food such as we handle and eat, it would be about as follows :

Beef, 13 oz.; butter, 2 oz.; potatoes, 6 oz.; bread, 20 oz.; for the meals of twenty-four hours. The Calorie value is about 3,400.

There seems to have been a very general agreement by authorities on the subject (up to very recent times) that the above quantities of food constituents were the minimum amount required by a man of average weight doing a moderate amount of muscular labor. Diminution in the protein was considered the most dangerous feature of underfeeding, and the hardest to recover from. It is only of very recent date that these figures have been criticized or questioned. The general principle that the ideal diet consisted of the smallest amount of protein (with carbohydrate added) that would serve to keep up body weight and vigor was emphasized by all investigators. The difficulty was that when it came to experiment, the data were gathered from lmman appetites and desires rather than from the actual needs of the body.

When we reflect upon how much of self-indulgence and gratification of the palate and how little of thought enters into the selection of what and how much we eat, we may realize how unsatisfactory and misleading must be the results deduced from such experiments.

Mr. Horace Fletcher was the Columbus who, with the aid of a professional man, Dr. Van Someren, first pointed out that exceptional health and vigor could be maintained upon one-half the amount recommended in the accepted dietaries.

The visit of Mr. Fletcher to the Yale University was epoch-making. He succeeded in interesting Prof. R. H. Chittenden, director of the Sheffield Scientific School, to such an extent that he was put in Professor Chittenden's laboratory for a period of thirteen days for the purpose of exact observation. The result was that a daily allowance of protein, 44.9 gm. (i}4 oz. nearly); fat, 38 gm. (i}{ oz.); carbohydrate, 253 gm. (8 J/2 oz.), kept Mr. Fletcher in nutritional equilibrium, although his weight is 165 pounds. The Calorie value of his food was about 1,600 per diem.

Then followed those well-known observations upon thirteen United States soldiers for a period of six months, which demonstrated that excellent health, increased vigor and full body weight could be maintained upon a dietary consisting of about one-half of the protein called for in standard dietaries, and this without any increase in carbohydrate.

These results were further extended and confirmed

THE DAILY AMOUNT OF FOOD. 25

by experiments upon five professional men and eight trained athletes, one of the latter winning championships in two college events while under the restricted diet.

These experiments were made upon different types of men and extended over sufficiently long periods of time to prove conclusively that there is no need for such quantities of food as the prevalent dietary standards call for. Health that was exceptional and increased vigor are fully proved thereby to be compatible with an amount of protein less by one-half, without any increase in fat and carbohydrates, than is demanded by the figures of Voit, Atwater and others. It is safe, in view of these recent experiments, to put the standard dietaries upon a new basis. There is no real physiological need for more than : Protein, 50 gm. (1^ oz.) ; fat, 50 gm. (1^ oz.) ; carbohydrate, 480 gm. (16 oz.).

This translated into quantities of plain food in its ordinary condition (not water free), would be : Beef, 5^ oz.; butter, 1^ oz.; potatoes, 6 oz.; bread, 19 oz.; for twenty-four hours, of which the Calorie value would be about 2,500.

An inevitable defect about averages is that, however true, they may not be applicable to particular individuals. It may be absolutely true, for instance, that the protein needs of a thousand men will average 120 gm. (4 oz.), but John Roe may be better off on that amount, and Richard Doe on one-half that amount. Moreover, what is applicable to a man at rest would be too little for him when at hard work, and as in daily life work cannot be measured, the varying needs of the individual must be largely guesswork, notwithstanding scientific averages. Professor Chittenden does not say that his subjects received just the proper amounts of food for their daily needs ; he simply claims to have demonstrated that health and vigor can be maintained on much less food than science has heretofore set down as the minimum. This was much, but there must be a "better way," according to Mr. Fletcher's phrase, for the individual to determine the kind and amount of food needed by the body for the varying factors of the rest and work of daily life.

This is the problem that Horace Fletcher has settled for all intelligent people who are willing to receive the information and pay the price of a little self-denial. With a full appreciation of the labors of Voit, Moleschott, Atwater, Playfair and others, it will one day be acknowledged that this simple discovery of Horace Fletcher (a layman) outweighs, or at least equals, in practical benefit to humanity all the valuable results obtained by these skilled professional scientists.

What is this momentous discovery that teaches what food to eat to meet the individual's needs, and how much to eat at a meal to match the ever- varying factors of rest and work, far better than averages deduced by the most stupendous labors from thousands of analyses ?

It is so simple that it seems lamentable, and even ridiculous, that it has not been discovered before. Hundreds of books on the physiology of digestion have mentioned the importance of chewing the food,

THE DAILY AMOUNT OF FOOD. 27

but none of them with the emphasis necessary to change one's habits entirely and produce far-reaching benefits. This discovery is simply the mastication of each mouthful of food until no taste is left in the morsel and the deglutition has been an involuntary process. Its simplicity is one of the formidable difficulties in the way of its general adoption ; people will climb mountains, take nauseous drugs, endure all kinds of disagreeable treatments to regain lost health, but this is too simple. Moreover, even when the mind is convinced and one starts in with the novel method, such is the inveterate persistence of long-standing bad habits that for a long period eternal vigilance becomes the price of rational mastication.