See R. Schröder,Lehrbuch der deutschen Rechtsgeschichte(1902), pp. 149, 508, 820, 880. Schröder gives a bibliography of monographs bearing on the history of the medieval diet.
See R. Schröder,Lehrbuch der deutschen Rechtsgeschichte(1902), pp. 149, 508, 820, 880. Schröder gives a bibliography of monographs bearing on the history of the medieval diet.
(E. Br.)
DIETARY,in a general sense, a system or course of diet, in the sense of food; more particularly, such an allowance and regulation of food as that supplied to workhouses, the army and navy, prisons, &c. Lowest in the scale of such dietaries comes what is termed “bare existence” diet, administered to certain classes of the community who have a claim on their fellow-countrymen that their lives and health shall be preservedin statu quo, but nothing further. This applies particularly to the members of a temporarily famine-stricken community. Before the days of prison reform, too, the dietary scale of many prisons was to a certain extent penal, in that the food supplied to prisoners was barely sufficient for existence. Nowadays more humane principles apply; there is no longer the obvious injustice of applying the same scale of quantity and quality to all prisoners under varying circumstances of constitution and surroundings, and whether serving long or short periods of imprisonment.
The system of dietary in force in the local and convict prisons of England and Wales is that recommended by the Home Office on the advice of a departmental committee. As to the local prison dietary, its application is based on (1) the principle of variation of diet with length of sentence; (2) the system of progressive dietary; (3) the distinction between hard labour diets and non-hard labour diets; (4) the differentiation of diet according to age and sex. There are three classes of diet, classes A, B and C. Class A diet is given to prisoners undergoing not more than seven days’ imprisonment. The food is good and wholesome, but sufficiently plain and unattractive, so as not to offer temptation to the loafer or mendicant. It is given in quantity sufficient to maintain health and strength during the single week. Prisoners sentenced to more than seven days and not more than fourteen days are given class A diet for the first seven days and class B for the remainder of the sentence. In most of the local prisons in England and Wales prisoners sentenced to hard labour received hard labour diet, although quite 60% were unable to perform the hardest forms of prison labour either through physical defect, age or infirmity. The departmental committee of 1899 in their report recommended that no distinction should be made between hard labour and non-hard labour diets. Class A diet is as follows:—Breakfast, Bread, 8 oz. daily (6 oz. for women and juveniles) with 1 pint of gruel. Juveniles (males and females undersixteen years of age) get, in addition, ½ pint of milk.Dinner, 8 oz. of bread daily, with 1 pint of porridge on three days of the week, 8 oz. of potatoes (representing the vegetable element) on two other days, and 8 oz. of suet pudding (representing the fatty element) on the other two days.Supper, the breakfast fare repeated.Class B diet, which is also given to (1) prisoners on remand or awaiting trial, (2) offenders of the 1st division who do not maintain themselves, (3) offenders of the 2nd division and (4) debtors, is as shown in Table I.Table I.Men.Women.Juveniles.Breakfast.Daily:—Bread8 oz.6 oz.6 oz.Gruel1 pt.1 pt.1 pt.Milk· ·· ·½ pt.Dinner.Sunday:—Bread6 oz.6 oz.Potatoes8 ”8 ”Cooked meat, preserved by heat4 ”3 ”Monday:—Bread6 oz.6 oz.Potatoes8 ”8 ”Beans10 ”8 ”Fat bacon2 ”1 ”Tuesday:—Bread6 oz6 oz.Potatoes8 ”8 ”Soup1 pt.1 pt.Wednesday:—Bread6 oz.6 oz.Potatoes8 ”8 ”Suet pudding10 ”8 ”Thursday:—Bread6 oz.6 oz.Potatoes8 ”8 ”Cooked beef, without bone4 ”3 ”Friday:—Bread6 oz.6 oz.Potatoes8 ”8 ”Soup1 pt.1 pt.Saturday:—Bread6 oz.6 oz.Potatoes8 ”8 ”Suet pudding10 ”8 ”Supper.Daily:—Bread8 oz.6 oz.6 oz.Porridge1 pt.Gruel1 pt.Cocoa1 pt.Class C diet is class B amplified, and is given to those prisoners serving sentences of three months and over.The dietary of convict prisons, in which prisoners are all under long sentence, is divided into a diet for convicts employed at hard labour and a diet for convicts employed at sedentary, indoor and light labour. It will be found set forth in the Blue-book mentioned above. The sparest of all prison diets is called “punishment diet,” and is administered for offences against the internal discipline of the prison. It is limited to a period of three days. It consists of 1 ℔ of bread and as much water as the prisoner chooses to drink.In French prisons the dietary is nearly two pounds weight of bread, with two meals of thin soup (breakfast and dinner) made from potatoes, beans or other vegetables, and on two days a week made from meat. In France the canteen system is in vogue, additional food, such as sausages, cheese, fruit, &c., may be obtained by the prisoner, according to the wages he receives for his labours. The dietary of Austrian prisons is 1½ ℔ of bread daily, a dinner of soup on four days of the week, and of meat on the other three days, with a supper of soup or vegetable stew. Additional food can be purchased by the prisoner out of his earnings.These dietaries may be taken as more or less typical of the ordinary prison fare in most civilized countries, though in some countries it may err on the side of severity, as in Sweden, prisoners being given only two meals a day, one at mid-day and one at seven p.m., porridge or gruel being the principal element in both meals. On the other hand, the prison dietaries of many of the United States prisons go to the other extreme, fresh fish, green vegetables, even coffee and fruit, figuring in the dietary.Another class of dietary is that given to paupers. In England, until 1900, almost every individual workhouse had its own special dietary, with the consequence that many erred on the side of scantiness and unsuitability, while others were too lavish. By an order of the Local Government Board of that year, acting on a report of a committee, all inmates of workhouses, with the exception of the sick, children under three years of age, and certain other special cases, are dieted in accordance with certain dietary tables as framed and settled by the board. The order contained a great number of different rations, it being left to the discretion of the guardians as to the final settlement of the tables. For adult inmates the dietary tables are for each sex respectively, two in number, one termed “plain diet” and the other “infirm diet.” All male inmates certified as healthy able-bodied persons receive plain diet only. All inmates, however, in workhouses are kept employed according to their capacity and ability, and this is taken into consideration in giving allowances of food. For instance, for work with sustained exertion, such as stone-breaking, digging, &c., more food is given than for work without sustained exertion, such as wood-chopping, weeding or sewing. Table II. shows an example of a workhouse dietary.Table II.Sun.Mon.Tue.Wed.Thu.Fri.Sat.Breakfast.Bread.oz.8444444Porridge.pt.*1½1½1½1½1½1½Dinner.Bread.oz.46..4486Beef.oz.4½......4½....Vegetables.oz.12....1212....Barley Soup.pt...1½..........Pork.oz.....4½........Beans.oz.....12........Fish.oz.......10......Cheese.oz...........3..Broth.pt...........1..Irish Stew.pt.............1Supper.Bread.oz.8666866Butter.oz.½............Tea.pt.1............Gruel.pt...1½1½1½..1½1½Broth.pt.........1....Cheese.oz.........2....* On Sundays 1 pint of tea and 2½ oz. of butter are given instead of porridge.In the casual wards of workhouses the dietary is plainer, consisting of 8 oz. of bread, or 6 oz. of bread and one pint of gruel or broth for breakfast; the same for supper; for dinner 8 oz. of bread and 1½ oz. of cheese or 6 oz. of bread and one pint of soup. The American poor law system is based broadly on that of England, and the methods of relief are much the same. Each state, however, makes its own regulations, and there is considerable diversity in workhouse dietaries in consequence. The German system of poor relief is more methodical than those of England and America. The really deserving are treatedwith more commiseration, and a larger amount of outdoor relief is given than in England. There is no casual ward, tramps and beggars being liable to penal treatment, but there are “relief stations,” somewhat corresponding to casual wards, where destitute persons tramping from one place to another can obtain food and lodging in return for work done.In the British navy certain staple articles of diet are supplied to the men to the value approximately of 6d. per diem—the standard government ration—and, in addition, a messing allowance of 4d. per diem, which may either be expended on luxuries in the canteen, or in taking up government provisions on board ship, in addition to the standard ration. The standard ration as recommended in 1907 by a committee appointed to inquire into the question of victualling in the navy is as follows:—Service Afloat.1 ℔ bread (or ¾ ℔ bread and ¼ ℔ trade flour).½ ℔ fresh meat.1 ℔ fresh vegetables.1⁄8pint spirit.4 oz. sugar.½ oz. tea (or 1 oz. coffee for every ¼ oz. tea).½ oz. ordinary or soluble chocolate (or 1 oz. coffee).¾ oz. condensed milk.1 oz. jam or marmalade.4 oz. preserved meat ononeday of the week in harbour, or ontwodays at sea.Mustard, pepper, vinegar, and salt as required.Substitute for soft bread when the latter is not available—½ ℔ biscuit (new type) or 1 ℔ flour.Substitutes for fresh meat when the latter is not available:—Onalternatedays.(1) Salt pork day:—½ ℔ salt pork.¼ ℔ split peas.Celery seed, ½ oz. to every 8 ℔ of split peas put into the coppers.½ ℔ potatoes (or 1 oz. compressed vegetables).(2) Preserved meat day:—6 oz. preserved meat.8 oz. trade flour}or 4 oz. rice.¾ oz. refined suet2 oz. raisins½ ℔ potatoes (or 1 oz. compressed vegetables).On shore establishments and depot ships ¼ pt. fresh milk is issued in lieu of the ¾ oz. of condensed milk.In the United States navy there is more liberality and variety of diet, the approximate daily cost of the rations supplied being 1s. 3d. per head. In the American mercantile marine, too, according to the scale sanctioned by act of Congress (December 21, 1898) for American ships, the seaman is better off than in the British merchant service. The scale is shown in Table III.Table III.WeeklyScale.Articles.WeeklyScale.Articles.3½ ℔Biscuits.7⁄8oz.Tea.3¾ ”Salt beef.21 ”Sugar.3 ”“ pork.1½ ℔Molasses.1½ ”Flour.9 oz.Fruits, dried.2 ”Meats, preserved.¾ pt.Pickles.10½ ”Bread, fresh (8 ℔ flour in lieu).1 ”Vinegar.1 ”Fish, dried.8 oz.Corn Meal.7 ”Potatoes or yams.12 ”Onions.1 ”Tomatoes, preserved.7 ”Lard.2⁄3”Peas.7 ”Butter.2⁄3”Calavances.¼ ”Mustard.2⁄3”Rice.¼ ”Pepper.5¼ oz.Coffee, green.¼ ”Salt.In the British mercantile marine there is no scale of provisions prescribed by the Board of Trade; there is, however, a traditional scale very generally adopted, having the sanction of custom only and seldom adhered to. The following dietary scale for steerage passengers, laid down in the 12th schedule of the Merchant Shipping Act 1894, is of interest. See Table IV.Table IV.—Weekly, per Statute Adult.Scale A.For voyages notexceeding 84 daysfor sailing shipsor 50 daysfor steamships.Scale B.For voyagesexceeding 84 daysfor sailing shipsor 50 daysfor steamships.℔ oz.℔ oz.Bread or biscuit, not inferior to navy biscuit3 83 8Wheaten flour1 02 0Oatmeal1 81 0Rice1 80 8Peas1 81 8Beef1 41 4Pork1 01 0Butter· ·0 4Potatoes2 02 0Sugar1 01 0Tea0 20 2Salt0 20 2Pepper (white or black), ground0 0½0 0½Vinegar1 gill1 gillPreserved meat· ·1 0Suet0 6Raisins0 8Lime juice0 6Certain substitutions may be made in this scale at the option of the master of any emigrant ship, provided that the substituted articles are set forth in the contract tickets of the steerage passengers.In the British army the soldier is fed partly by a system of co-operation. He gets a free ration from government of 1 ℔ of bread and ¾ ℔ of meat; in addition there is a messing allowance of 3½d. per man per day. He is able to supplement his food by purchases from the canteen. Much depends on the individual management in each regiment as to the satisfactory expenditure of the messing allowance. In some regiments an allowance is made from the canteen funds towards messing in addition to that granted by the government. The ordinaryfieldration of the British soldier is 1½ ℔ of bread or 1 ℔ of biscuit; 1 ℔ of fresh, salt or preserved meat; ½ oz. of coffee; 1/6 oz. of tea; 2 oz. of sugar; ½ oz. of salt,1⁄36oz. of pepper, the whole weighing something over 2 ℔ 3 oz. This cannot be looked on as a fixed ration, as it varies in different campaigns, according to the country into which the troops may be sent. The Prussian soldier during peace gets weekly from his canteen 11 ℔ 1 oz. of rye bread and not quite 2½ ℔ of meat. This is obviously insufficient, but underthe conscription system it is reckoned that he will be able to make up the deficiency out of his own private means, or obtain charitable contributions from his friends. In the French infantry of the line each man during peace gets weekly 15 ℔ of bread, 33⁄10℔ of meat, 2½ ℔ of haricot beans or other vegetables, with salt and pepper, and 1¾ oz. of brandy.An Austrian under the same circumstances receives 13.9 ℔ of bread, ½ ℔ of flour and 3.3 ℔ of meat.The Russian conscript is allowed weekly:—Black bread7 ℔.Meat7 ℔.Kvass (beer)7.7 quarts.Sour cabbage24½ gills = 122½ oz.Barley24½ gills = 122½ oz.Salts10½ oz.Horse-radish28 grains.Pepper28 grains.Vinegar5½ gills = 26½ oz.
The system of dietary in force in the local and convict prisons of England and Wales is that recommended by the Home Office on the advice of a departmental committee. As to the local prison dietary, its application is based on (1) the principle of variation of diet with length of sentence; (2) the system of progressive dietary; (3) the distinction between hard labour diets and non-hard labour diets; (4) the differentiation of diet according to age and sex. There are three classes of diet, classes A, B and C. Class A diet is given to prisoners undergoing not more than seven days’ imprisonment. The food is good and wholesome, but sufficiently plain and unattractive, so as not to offer temptation to the loafer or mendicant. It is given in quantity sufficient to maintain health and strength during the single week. Prisoners sentenced to more than seven days and not more than fourteen days are given class A diet for the first seven days and class B for the remainder of the sentence. In most of the local prisons in England and Wales prisoners sentenced to hard labour received hard labour diet, although quite 60% were unable to perform the hardest forms of prison labour either through physical defect, age or infirmity. The departmental committee of 1899 in their report recommended that no distinction should be made between hard labour and non-hard labour diets. Class A diet is as follows:—Breakfast, Bread, 8 oz. daily (6 oz. for women and juveniles) with 1 pint of gruel. Juveniles (males and females undersixteen years of age) get, in addition, ½ pint of milk.Dinner, 8 oz. of bread daily, with 1 pint of porridge on three days of the week, 8 oz. of potatoes (representing the vegetable element) on two other days, and 8 oz. of suet pudding (representing the fatty element) on the other two days.Supper, the breakfast fare repeated.
Class B diet, which is also given to (1) prisoners on remand or awaiting trial, (2) offenders of the 1st division who do not maintain themselves, (3) offenders of the 2nd division and (4) debtors, is as shown in Table I.
Table I.
Class C diet is class B amplified, and is given to those prisoners serving sentences of three months and over.
The dietary of convict prisons, in which prisoners are all under long sentence, is divided into a diet for convicts employed at hard labour and a diet for convicts employed at sedentary, indoor and light labour. It will be found set forth in the Blue-book mentioned above. The sparest of all prison diets is called “punishment diet,” and is administered for offences against the internal discipline of the prison. It is limited to a period of three days. It consists of 1 ℔ of bread and as much water as the prisoner chooses to drink.
In French prisons the dietary is nearly two pounds weight of bread, with two meals of thin soup (breakfast and dinner) made from potatoes, beans or other vegetables, and on two days a week made from meat. In France the canteen system is in vogue, additional food, such as sausages, cheese, fruit, &c., may be obtained by the prisoner, according to the wages he receives for his labours. The dietary of Austrian prisons is 1½ ℔ of bread daily, a dinner of soup on four days of the week, and of meat on the other three days, with a supper of soup or vegetable stew. Additional food can be purchased by the prisoner out of his earnings.
These dietaries may be taken as more or less typical of the ordinary prison fare in most civilized countries, though in some countries it may err on the side of severity, as in Sweden, prisoners being given only two meals a day, one at mid-day and one at seven p.m., porridge or gruel being the principal element in both meals. On the other hand, the prison dietaries of many of the United States prisons go to the other extreme, fresh fish, green vegetables, even coffee and fruit, figuring in the dietary.
Another class of dietary is that given to paupers. In England, until 1900, almost every individual workhouse had its own special dietary, with the consequence that many erred on the side of scantiness and unsuitability, while others were too lavish. By an order of the Local Government Board of that year, acting on a report of a committee, all inmates of workhouses, with the exception of the sick, children under three years of age, and certain other special cases, are dieted in accordance with certain dietary tables as framed and settled by the board. The order contained a great number of different rations, it being left to the discretion of the guardians as to the final settlement of the tables. For adult inmates the dietary tables are for each sex respectively, two in number, one termed “plain diet” and the other “infirm diet.” All male inmates certified as healthy able-bodied persons receive plain diet only. All inmates, however, in workhouses are kept employed according to their capacity and ability, and this is taken into consideration in giving allowances of food. For instance, for work with sustained exertion, such as stone-breaking, digging, &c., more food is given than for work without sustained exertion, such as wood-chopping, weeding or sewing. Table II. shows an example of a workhouse dietary.
Table II.
In the casual wards of workhouses the dietary is plainer, consisting of 8 oz. of bread, or 6 oz. of bread and one pint of gruel or broth for breakfast; the same for supper; for dinner 8 oz. of bread and 1½ oz. of cheese or 6 oz. of bread and one pint of soup. The American poor law system is based broadly on that of England, and the methods of relief are much the same. Each state, however, makes its own regulations, and there is considerable diversity in workhouse dietaries in consequence. The German system of poor relief is more methodical than those of England and America. The really deserving are treatedwith more commiseration, and a larger amount of outdoor relief is given than in England. There is no casual ward, tramps and beggars being liable to penal treatment, but there are “relief stations,” somewhat corresponding to casual wards, where destitute persons tramping from one place to another can obtain food and lodging in return for work done.
In the British navy certain staple articles of diet are supplied to the men to the value approximately of 6d. per diem—the standard government ration—and, in addition, a messing allowance of 4d. per diem, which may either be expended on luxuries in the canteen, or in taking up government provisions on board ship, in addition to the standard ration. The standard ration as recommended in 1907 by a committee appointed to inquire into the question of victualling in the navy is as follows:—
Service Afloat.
1 ℔ bread (or ¾ ℔ bread and ¼ ℔ trade flour).½ ℔ fresh meat.1 ℔ fresh vegetables.1⁄8pint spirit.4 oz. sugar.½ oz. tea (or 1 oz. coffee for every ¼ oz. tea).½ oz. ordinary or soluble chocolate (or 1 oz. coffee).¾ oz. condensed milk.1 oz. jam or marmalade.4 oz. preserved meat ononeday of the week in harbour, or ontwodays at sea.Mustard, pepper, vinegar, and salt as required.
1 ℔ bread (or ¾ ℔ bread and ¼ ℔ trade flour).
½ ℔ fresh meat.
1 ℔ fresh vegetables.
1⁄8pint spirit.
4 oz. sugar.
½ oz. tea (or 1 oz. coffee for every ¼ oz. tea).
½ oz. ordinary or soluble chocolate (or 1 oz. coffee).
¾ oz. condensed milk.
1 oz. jam or marmalade.
4 oz. preserved meat ononeday of the week in harbour, or ontwodays at sea.
Mustard, pepper, vinegar, and salt as required.
Substitute for soft bread when the latter is not available—
½ ℔ biscuit (new type) or 1 ℔ flour.
Substitutes for fresh meat when the latter is not available:—
On shore establishments and depot ships ¼ pt. fresh milk is issued in lieu of the ¾ oz. of condensed milk.
In the United States navy there is more liberality and variety of diet, the approximate daily cost of the rations supplied being 1s. 3d. per head. In the American mercantile marine, too, according to the scale sanctioned by act of Congress (December 21, 1898) for American ships, the seaman is better off than in the British merchant service. The scale is shown in Table III.
Table III.
In the British mercantile marine there is no scale of provisions prescribed by the Board of Trade; there is, however, a traditional scale very generally adopted, having the sanction of custom only and seldom adhered to. The following dietary scale for steerage passengers, laid down in the 12th schedule of the Merchant Shipping Act 1894, is of interest. See Table IV.
Table IV.—Weekly, per Statute Adult.
Certain substitutions may be made in this scale at the option of the master of any emigrant ship, provided that the substituted articles are set forth in the contract tickets of the steerage passengers.
In the British army the soldier is fed partly by a system of co-operation. He gets a free ration from government of 1 ℔ of bread and ¾ ℔ of meat; in addition there is a messing allowance of 3½d. per man per day. He is able to supplement his food by purchases from the canteen. Much depends on the individual management in each regiment as to the satisfactory expenditure of the messing allowance. In some regiments an allowance is made from the canteen funds towards messing in addition to that granted by the government. The ordinaryfieldration of the British soldier is 1½ ℔ of bread or 1 ℔ of biscuit; 1 ℔ of fresh, salt or preserved meat; ½ oz. of coffee; 1/6 oz. of tea; 2 oz. of sugar; ½ oz. of salt,1⁄36oz. of pepper, the whole weighing something over 2 ℔ 3 oz. This cannot be looked on as a fixed ration, as it varies in different campaigns, according to the country into which the troops may be sent. The Prussian soldier during peace gets weekly from his canteen 11 ℔ 1 oz. of rye bread and not quite 2½ ℔ of meat. This is obviously insufficient, but under
the conscription system it is reckoned that he will be able to make up the deficiency out of his own private means, or obtain charitable contributions from his friends. In the French infantry of the line each man during peace gets weekly 15 ℔ of bread, 33⁄10℔ of meat, 2½ ℔ of haricot beans or other vegetables, with salt and pepper, and 1¾ oz. of brandy.
An Austrian under the same circumstances receives 13.9 ℔ of bread, ½ ℔ of flour and 3.3 ℔ of meat.
The Russian conscript is allowed weekly:—
DIETETICS,the science of diet,i.e.the food and nutrition of man in health and disease (seeNutrition). This article deals mainly with that part of the subject which has to do with the composition and nutritive values of foods and their adaptation to the use of people in health. The principal topics considered are: (1) Food and its functions; (2) Metabolism of matter and energy; (3) Composition of food materials; (4) Digestibility of food; (5) Fuel value of food; (6) Food consumption; (7) Quantities of nutrients needed; (8) Hygienic economy of food; (9) Pecuniary economy of food.
1.Food and its Functions.—For practical purposes, food may be defined as that which, when taken into the body, may be utilized for the formation and repair of body tissue, and the production of energy. More specifically, food meets the requirements of the body in several ways. It is used for the formation of the tissues and fluids of the body, and for the restoration of losses of substance due to bodily activity. The potential energy of the food is converted into heat or muscular work or other forms of energy. In being thus utilized, food protects body substance or previously acquired nutritive material from consumption. When the amountof food taken into the body is in excess of immediate needs, the surplus may be stored for future consumption.
Ordinary food materials, such as meat, fish, eggs, vegetables, &c., consist of inedible materials, orrefuse,e.g.bone of meat and fish, shell of eggs, rind and seed of vegetables; andedible material, as flesh of meat and fish, white and yolk of eggs, wheat flour, &c. The edible material is by no means a simple substance, but consists ofwater, and some or all of the compounds variously designated as food stuffs, proximate principles, nutritive ingredients or nutrients, which are classified asprotein,fats,carbohydratesandmineral matters. These have various functions in the nourishment of the body.
Therefusecommonly contains compounds similar to those in the food from which it is derived, but since it cannot be eaten, it is usually considered as a non-nutrient. It is of importance chiefly in a consideration of the pecuniary economy of food.Wateris also considered as a non-nutrient, because although it is a constituent of all the tissues and fluids of the body, the body may obtain the water it needs from that drunk; hence, that contained in the food materials is of no special significance as a nutrient.
Mineral matters, such as sulphates, chlorides, phosphates and carbonates of sodium, potassium, calcium, &c., are found in different combinations and quantities in most food materials. These are used by the body in the formation of the various tissues, especially the skeletal and protective tissues, in digestion, and in metabolic processes within the body. They yield little or no energy, unless perhaps the very small amount involved in their chemical transformation.
Protein1is a term used to designate the whole group of nitrogenous compounds of food except the nitrogenous fats. It includes the albuminoids, as albumin of egg-white, and of blood serum, myosin of meat (muscle), casein of milk, globulin of blood and of egg yolk, fibrin of blood, gluten of flour; the gelatinoids, as gelatin and allied substances of connective tissue, collagen of tendon, ossein of bone and the so-called extractives (e.g.creatin) of meats; and the amids (e.g.asparagin) and allied compounds of vegetables and fruits.
The albuminoids and gelatinoids, classed together as proteids, are the most important constituents of food, because they alone can supply the nitrogenous material necessary for the formation of the body tissues. For this purpose, the albuminoids are most valuable. Both groups of compounds, however, supply the body with energy, and the gelatinoids in being thus utilized protect the albuminoids from consumption for this purpose. When their supply in the food is in excess of the needs of the body, the surplus proteids may be converted into body fat and stored.
The so-called extractives, which are the principal constituents of meat extract, beef tea and the like, act principally as stimulants and appetizers. It has been believed that they serve neither to build tissue nor to yield energy, but recent investigations2indicate that creatin may be metabolized in the body.
Thefatsof food include both the animal fats and the vegetable oils. Thecarbohydratesinclude such compounds as starches, sugars and the fibre of plants or cellulose, though the latter has but little value as food for man. The more important function of both these classes of nutrients is to supply energy to the body to meet its requirements above that which it may obtain from the proteids. It is not improbable that the atoms of their molecules as well as those from the proteids are built up into the protoplasmic substance of the tissues. In this sense, these nutrients may be considered as being utilized also for the formation of tissue; but they are rather the accessory ingredients, whereas the proteids are the essential ingredients for this purpose. The fats in the food in excess of the body requirements may be stored as body fat, and the surplus carbohydrates may also be converted into fat and stored.
To a certain extent, then, the nutrients of the food may substitute each other. All may be incorporated into the protoplasmic structure of body tissue, though only the proteids can supply the essential nitrogenous ingredients; and apart from the portion of the proteid material that is indispensable for this purpose, all the nutrients are used as a source of energy. If the supply of energy in the food is not sufficient, the body will use its own proteid and fat for this purpose. The gelatinoids, fats and carbohydrates in being utilized for energy protect the body proteids from consumption. The fat stored in the body from the excess of food is a reserve of energy material, on which the body may draw when the quantity of energy in the food is insufficient for its immediate needs.
What compounds are especially concerned in intellectual activity is not known. The belief that fish is especially rich in phosphorus and valuable as a brain food has no foundation in observed fact.
2.Metabolism of Matter and Energy.—The processes of nutrition thus consist largely of the transformation of food into body material and the conversion of the potential energy of both food and body material into the kinetic energy of heat and muscular work and other forms of energy. These various processes are generally designated by the term metabolism. The metabolism of matter in the body is governed largely by the needs of the body for energy. The science of nutrition, of which the present subject forms a part, is based on the principle that the transformations of matter and energy in the body occur in accordance with the laws of the conservation of matter and of energy. That the body can neither create nor destroy matter has long been universally accepted. It would seem that the transformation of energy must likewise be governed by the law of the conservation of energy; indeed there is every reason a priori to believe that it must; but the experimental difficulties in the way of absolute demonstration of the principle are considerable. For such demonstration it is necessary to prove that the income and expenditure of energy are equal. Apparatus and methods of inquiry devised in recent years, however, afford means for a comparison of the amounts of both matter and energy received and expended by the body, and from the results obtained in a large amount of such research, it seems probable that the law obtains in the living organism in general.
The first attempt at such demonstration was made by M. Rubner3in 1894, experimenting with dogs doing no external muscular work. The income of energy (as heat) was computed, but the heat eliminated was measured. In the average of eight experiments continuing forty-five days, the two quantities agreed within 0.47%, thus demonstrating what it was desired to prove—that the heat given off by the body came solely from the oxidation of food within it. Results in accordance with these were reported by Studenski4in 1897, and by Laulanie5in 1898.
The most extensive and complete data yet available on the subject have been obtained by W. O. Atwater, F. G. Benedict and associates6in experiments with men in the respiration calorimeter, in which a subject may remain for several consecutive days and nights. These experiments involve actual weighing and analyses of the food and drink, and of the gaseous, liquid and solid excretory products; determinations of potential energy (heat of oxidation) of the oxidizable material received and given off by the body (including estimation of the energy of the material gained or lost by the body); and measurements of the amounts of energy expended as heat and as external muscular work. By October 1906 eighty-eight experiments with fifteen different subjects had been completed. The separate experiments continued from two to thirteen days, making a total of over 270 days.In some cases the subjects were at rest; in others they performed varying amounts of external muscular work on an apparatus by means of which the amount of work done was measured. In some cases they fasted, and in others they received diets generally not far from sufficient to maintain nitrogen, and usually carbon, equilibrium in the body. In these experiments the amount of energy expended by the body as heat and as external muscular work measured in terms of heat agreed on the average very closely with the amount of heat that would be produced by the oxidation of all the matter metabolized in the body. The variations for individual days, and in the average for individual experiments as well, were in some cases appreciable, amounting to as much as 6%, which is not strange in view of the uncertainties in physiological experimenting; but in the average of all the experiments the energy of the expenditure was above 99.9% of the energy of the income,—an agreement within one part in 1000. While these results do not absolutely prove the application of the law of the conservation of energy in the human body, they certainly approximate very closely to such demonstration. It is of course possible that energy may have given offfrom the body in other forms than heat and external muscular work. It is conceivable, for example, that intellectual activity may involve the transformation of physical energy, and that the energy involved may be eliminated in some form now unknown. But if the body did give off energy which was not measured in these experiments, the quantity must have been extremely small. It seems fair to infer from the results obtained that the metabolism of energy in the body occurred in conformity with the law of the conservation of energy.
3.Composition of Food Materials.—The composition of food is determined by chemical analyses, the results of which are conventionally expressed in terms of the nutritive ingredients previously described. As a result of an enormous amount of such investigation in recent years, the kinds and proportions of nutrients in our common sorts of food are well known. Average values for percentage composition of some ordinary food materials are shown in Table I. (Table I. also includes figures for fuel value.)
Table I.—Percentage Composition of some Common Food Materials.
It will be observed that different kinds of food materials vary widely in their proportions of nutrients. In general the animal foods contain the most protein and fats, and vegetable foods are rich in carbohydrates. The chief nutrient of lean meat and fish is protein; but in medium fat meats the proportion of fat is as large as that of protein, and in the fatter meats it is larger. Cheese is rich in both protein and fat. Among the vegetable foods, dried beans and peas are especially rich in protein. The proportion in oatmeal is also fairly large, in wheat it is moderate, and in maize meal and rice it is rather small. Oats contain more oil than any of the common cereals, but in none of them is the proportion especially large. The most abundant nutrient in all the cereals is starch, which comprises from two-thirds to three-fourths or more of their total nutritive substance. Cotton-seed is rich in edible oil, and so are olives. Some of the nuts contain fairly large proportions of both protein and fat. The nutrient of potatoes is starch, present in fair proportion. Fruits contain considerable carbohydrates, chiefly sugar. Green vegetables are not of much account as sources of any of the nutrients or energy.
Similar food materials from different sources may also differ considerably in composition. This is especially true of meats. Thus, the leaner portions from a fat animal may contain nearly as much fat as the fatter portions from a lean animal. The data here presented are largely those for American food products, but the available analyses of English food materials indicate that the latter differ but little from the former in composition. The analyses of meats produced in Europe imply that they commonly contain somewhat less fat and more water, and often more protein, than American meats. The meats of English production compare with the American more than with the European meats. Similar vegetable foods from the different countries do not differ so much in composition.
4.Digestibility or Availability of Food Materials.—The value of any food material for nutriment depends not merely upon the kinds and amounts of nutrients it contains, but also upon the ease and convenience with which the nutrients may be digested, and especially upon the proportion of the nutrients that will be actually digested and absorbed. Thus, two foods may contain equal amounts of the same nutrient, but the one most easily digested will really be of most value to the body, because less effort is necessary to utilize it. Considerable study of this factor is being made, and much valuable information is accumulating, but it is of more especial importance in cases of disordered digestion.
The digestibility of food in the sense of thoroughness of digestion, however, is of particular importance in the present discussion. Only that portion of the food that is digested and absorbed is available to the body for the building of tissue and the production of energy. Not all the food eaten is thus actually digested; undigested material is excreted in the faeces. The thoroughness of digestion is determined experimentally by weighing and analysing the food eaten and the faeces pertaining to it. The difference between the corresponding ingredients of the two is commonly considered to represent the amounts of the ingredients digested. Expressed in percentages, these are called coefficients of digestibility. See Table II.
Table II.—Coefficients of Digestibility (or Availability) of Nutrients in Different Classes of Food Materials.
Such a method is not strictly accurate, because the faeces do not consist entirely of undigested food but contain in addition to this the so-called metabolic products, which include the residuum of digestive juices not resorbed, fragments of intestinal epithelium, &c. Since there is as yet no satisfactory method of separating these constituents of the excreta, the actual digestibility of the food is not determined. It has been suggested that since these materials must originally come from food, they represent, when expressed in terms of food ingredients, the cost of digestion; hence that the values determined as above explained represent the portion of food available to the body for the building of tissue and the yielding of energy, and what is commonly designated as digestibility should be called availability. Other writers retain the term “digestibility,” but express the results as “apparent digestibility,” until more knowledge regarding the metabolic products of the excreta is available and the actual digestibility may be ascertained.
Experimental inquiry of this nature has been very active in recent years, especially in Europe, the United States and Japan; and the results of considerably over 1000 digestion experiments with single foods or combinations of food materials are available. These were mostly with men, but some were with women and with children. The larger part of these have been taken into account in the following estimations of the digestibility of the nutrients in different classes of food materials. The figures here shown are subject to revision as experimental data accumulate. They are not to be taken as exact measures of the digestibility (or availability) of every kind of food in each given class, but they probably represent fairly well the average digestibility of the classes of food materials as ordinarily utilized in the mixed diet.
5.Fuel Value of Food.—The potential energy of food is commonly measured as the amount of heat evolved when the food is completely oxidized. In the laboratory this is determined by burning the food in oxygen in a calorimeter. The results, which are known as the heat of combustion of the food, areexpressed in calories, one calory being the amount of heat necessary to raise the temperature of one kilogram of water one degree centigrade. But it is to be observed that this unit is employed simply from convenience, and without implication as to what extent the energy of food is converted into heat in the body. The unit employed in the measurement of some other form of energy might be used instead, as, for example, the foot-ton, which represents the amount of energy necessary to raise one ton through one foot.
Table III.—Estimates of Heats of Combustion and of Fuel Value of Nutrients in Ordinary Mixed Diet.
The amount of energy which a given quantity of food will produce on complete oxidation outside the body, however, is greater than that which the body will actually derive from it. In the first place, as previously shown, part of the food will not be digested and absorbed. In the second place, the nitrogenous compounds absorbed are not completely oxidized in the body, the residuum being excreted in the urine as urea and other bodies that are capable of further oxidation in the calorimeter. The total heat of combustion of the food eaten must therefore be diminished by the heat of combustion of the oxidizable material rejected by the body, to find what amount of energy is actually available to the organism for the production of work and heat. The amount thus determined is commonly known as the fuel value of food.
Rubner’s7commonly quoted estimates for the fuel value of the nutrients of mixed diet are,—for protein and carbohydrates 4.1, and for fats 9.3 calories per gram. According to the method of deduction, however, these factors were more applicable to digested than to total nutrients. Atwater8and associates have deduced, from data much more extensive than those available to Rubner, factors for total nutrients somewhat lower than these, as shown in Table III. These estimates seem to represent the best average factors at present available, but are subject to revision as knowledge is extended.
Table IV.—Quantities of Available Nutrients and Energy in Daily Food Consumption of Persons in Different Circumstances.