Part 21

Fuel Values of Nutrients.--In experiments performed by Professor Atwater and others, and in the appended tables, the value of food as a source of energy is stated in heat units called _Calories_. _A Calorie is the amount of heat required to raise the temperature of one kilogram of water from zero to one degree Centigrade._ This is about equivalent to raising one pound four degrees Fahrenheit. The fuel value of different foods may be computed in a definite manner. This is done by burning a given portion of a food (say one gram) in the apparatus known as a _calorimeter_. By this means may be determined the number of degrees the temperature of a given amount of water is raised during the process of burning. It has thus been found that a gram of fat will liberate 9.3 Calories of heat, while a gram of starch or sugar only about 4 Calories. The burning value of fat is, therefore, over twice that of carbohydrates. In a similar manner protein has been shown to have about the same fuel value as carbohydrates, _i.e._ 4 Calories to a gram.[38]

Footnote 37 and 38: W. O. Atwater, _Principles of Nutrition and Nutritive Value of Food_, U. S. Department of Agriculture, 1902.

The Relation of Work to Diet.--It has been shown experimentally that a man doing hard, muscular work needs more food than a person doing light work. The mere exercise gives the individual a hearty appetite; he eats more and needs more of all kinds of food than a man or boy doing light work. Especially is it true that the person of sedentary habits, who does brain work, should be careful to eat less food and food that will digest easily. His protein food should also be reduced. Rich or hearty foods may be left for the man who is doing hard manual labor out of doors, for any extra work put on the digestive organs takes away just so much from the ability of the brain to do its work.

The Relation of Environment to Diet.--We are all aware of the fact that the body seems to crave more food in winter than in summer. The temperature of the body is maintained at 98.6 deg. in winter as in summer, but much more heat is lost from the body in cold weather. Hence feeding in winter should be for the purpose of maintaining our fuel supply. We need heat-producing food, and we need _more_ food in winter than in summer. We may use carbohydrates for this purpose, as they are economical and digestible. The inhabitants of cold countries get their heat-releasing foods largely from fats. In tropical countries and in hot weather little protein should be eaten and a considerable amount of fresh fruit used.

The Relation of Age to Diet.--As we will see a little later, age is a factor not only in determining the kind but the amount of food to be used. Young children require far less food than do those of older growth or adults. The body constantly increases in weight until young manhood, or womanhood, then its weight remains nearly stationary, varying with health or illness. It is evident that food in adults simply repairs the waste of cells and is used to supply energy. Elderly people need much less protein than do younger persons. But inasmuch as the amount of food to be taken into the body should be in proportion to the body weight, it is also evident that growing children do not, as is popularly supposed, need as much food as grown-ups.

The Relation of Sex to Diet.--As a rule boys need more food than girls, and men than women. This seems to be due to, first, the more active muscular life of the man and, secondly, to the greater amount of fat in the tissues of the woman, making loss of heat less. Larger bodies, because of greater surface, give off more heat than smaller ones. Men are usually larger in bulk than are women,--another reason for more food in their case.

The Relation of Digestibility to Diet.--Animal foods in general may be said to be more completely digested within the body than plant foods. This is largely due to the fact that plant cells have woody walls that the digestive juices cannot act upon. Cereals and legumes are less digestible foods than are dairy products, meat, or fish. This does not mean necessarily that these foods would not agree with you or me but that in general the body would get less nourishment out of the total amount available.

The agreement or disagreement of food with an individual is largely a personal matter. I, for example, cannot eat raw tomatoes without suffering from indigestion, while some one else can digest tomatoes but not strawberries. Each individual should learn early in life the foods that disagree with him personally and leave such foods out of his dietary. For "what is one man's meat may be another man's poison."

The Relation of Cost of Food to Diet.--It is a mistaken notion that the best foods are always the most expensive. A glance at the table (page 283) will show us that both fuel value and tissue-building value is present in some foods from vegetable sources, as well as in those from animal sources, and that the vegetable foods are much cheaper. The American people are far less economical in their purchase of food than most other nations. Nearly one half of the total income of the average workingman is spent on food. Not only does he spend a large amount on food, but he wastes money in purchasing the wrong kinds of food. A comparison of the daily diets of persons in various occupations in this and other countries shows that as a rule we eat more than is necessary to supply the necessary fuel and repair, and that our workingmen eat more than those of other countries. Another waste of money by the American is in the false notion that a large proportion of the daily dietary should be meat. Many people think that the most expensive cuts of meat are the most nutritious. The falsity of this idea may be seen by a careful study of the tables on pages 283 and 286.

The Best Dietary.--Inasmuch as all living substance contains nitrogen, it is evident that protein food must form a part of the dietary; but protein alone is not usable. If more protein is eaten than the body requires, then immediately the liver and kidneys have to work overtime to get rid of the excess of protein which forms a poisonous waste harmful to the body. We must take foods that will give us, as nearly as possible, the proportion of the different chemical elements as they are contained in protoplasm. It has been found, as a result of studies of Atwater and others, that a man who does muscular work requires a little less than one quarter of a pound of protein, the same amount of fat, and about one pound of carbohydrate to provide for the growth, waste, and repair of the body and the energy used up in one day.

The Daily Calorie Requirement.--Put in another way, Atwater's standard for a man at light exercise is food enough to yield 2816 Calories; of these, 410 Calories are from protein, 930 Calories from fat, and 1476 Calories from carbohydrate. That is, for every 100 Calories furnished by the food, 14 are from protein, 32 from fat, and 54 from carbohydrate. In exact numbers, the day's ration as advocated by Atwater would contain about 100 grams or 3.7 ounces protein, 100 grams or 3.7 ounces fat, and 360 grams or 13 ounces carbohydrate. Professor Chittenden of Yale University, another food expert, thinks we need proteins, fats, and carbohydrates in about the proportion of 1 to 3 to 6, thus differing from Atwater in giving less protein in proportion. Chittenden's standard for the same man is food to yield a total of 2360 Calories, of which protein furnishes 236 Calories, fat 708 Calories, and carbohydrates 1416 Calories. For every 100 Calories furnished by the food, 10 are from protein, 30 from fat, 60 from carbohydrate. In actual amount the Chittenden diet would contain 2.16 ounces protein, 2.83 ounces fat, and 13 ounces carbohydrate. A German named Voit gives as ideal 25 Calories from proteins, 20 from fat, and 55 from carbohydrate, out of every 100 Calories; this is nearer our actual daily ration. In addition, an ounce of salt and nearly one hundred ounces of water are used in a day.

A Mixed Diet Best.--Knowing the proportion of the different food substances required by man, it will be an easy matter to determine from the tables and charts shown you the best foods for use in a mixed diet. Meats contain too much nitrogen in proportion to the other substances. In milk, the proportion of proteins, carbohydrates, and fats is nearly right to make protoplasm; a considerable amount of mineral matter being also present. For these reasons, milk is extensively used as a food for children, as it combines food material for the forming of protoplasm with mineral matter for the building of bone. Some vegetables (for example, peas and beans) contain a large amount of nitrogenous material but in a less digestible form than is found in some other foods. Vegetarians, then, are correct in theory when they state that a diet of vegetables may contain everything necessary to sustain life. But a mixed diet containing meat is healthier. A purely vegetable diet contains much waste material, such as the cellulose forming the walls of plant cells, which is indigestible. It has been recently discovered that the outer coats of some grains, as rice, contain certain substances (enzymes) which aid in digestion. In the case of polished rice, when this outer coat is removed the grain has much less food value.

Daily Fuel Needs of the Body.--It has been pointed out that the daily diet should differ widely according to age, occupation, time of year, etc. The following table shows the daily fuel needs for several ages and occupations:--

DAILY CALORIE NEEDS (APPROXIMATELY)

1. For child under 2 years 900 Calories 2. For child from 2-5 years 1200 Calories 3. For child from 6-9 years 1500 Calories 4. For child from 10-12 years 1800 Calories 5. For child from 12-14 (woman, light work, also) 2100 Calories 6. For boy (12-14), girl (15-16), man, sedentary 2400 Calories 7. For boy (15-16) (man, light muscular work) 2700 Calories 8. For man, moderately active muscular work 3000 Calories 9. For farmer (busy season) 3200 to 4000 Calories 10. For ditchers, excavators, etc. 4000 to 5000 Calories 11. For lumbermen, etc. 5000 and more Calories

Normal Heat Output.--The following table gives the result of some experiments made to determine the hourly and daily expenditure of energy of the average normal grown person when asleep and awake, at work or at rest:--

AVERAGE NORMAL OUTPUT OF HEAT FROM THE BODY ========================================================== | AVERAGE CONDITIONS OF MUSCULAR ACTIVITY | CALORIES | PER HOUR -------------------------------------------+-------------- Man at rest, sleeping | 65 Calories Man at rest, awake, sitting up | 100 Calories Man at light muscular exercise | 170 Calories Man at moderately active muscular exercise | 290 Calories Man at severe muscular exercise | 450 Calories Man at very severe muscular exercise | 600 Calories ==========================================================

It is very simple to use such a table in calculating the number of Calories which are spent in twenty-four hours under different bodily conditions. For example, suppose the case of a clerk or school teacher leading a relatively inactive life, who

sleeps for 9 hours x 65 Calories = 585 works at desk 9 hours x 100 Calories = 900 reads, writes, or studies 4 hours x 100 Calories = 400 walks or does light exercise 2 hours x 170 Calories = 340 ---- 2225

This comes out, as we see, very close to example 6 of the table[39] on page 284.

Footnote 39: The above tables have been taken from the excellent pamphlet of the Cornell Reading Course, No. 6, _Human Nutrition_.

How we may Find whether we are Eating a properly Balanced Diet.--We already know approximately our daily Calorie needs and about the proportion of protein, fat, and carbohydrate needed. Dr. Irving Fisher of Yale University has worked out a very easy method of determining whether one is living on a proper diet. He has made up a number of tables, in which he has designated portions of food, each of which furnishes 100 Calories of energy. The tables show the proportion of protein, fat, and carbohydrate in each food, so that it is a simple matter by using such a table to estimate the proportions of the various nutrients in our dietary. We may depend upon taking somewhere near the proper amount of food if we take a diet based upon either Atwater's, Chittenden's, or Voit's standard. One of the most interesting and useful pieces of home work that you can do is to estimate your own personal dietary, using the tables giving the 100-Calorie portion to see if you have a properly balanced diet. From the table on page 286 make out a simple dietary for yourself for one day, estimating your own needs in Calories and then picking out 100-Calorie portions of food which will give you the proper proportions of protein, fat, and carbohydrate.

TABLE OF 100 CALORIE PORTIONS--MODIFIED FROM FISHER

============================================================================ | |WT. IN| CAL. FURNISHED| PRICE | | OZ. |----+----+-----+--------+------ |PORT. CONTAINING | 100 | | |CAR- | | 100 FOOD | 100 CALORIES | CAL.|PRO-| FAT|BOHY-| 1 LB. | CAL. | | PORT.|TEIN| |DRATE| | POR. ------------------+------------------+------+----+----+-----+--------+------ Oysters |1 doz. | 6.8 | 49 |22 | 29 | .175 | .07 Bean soup |1/2 small serving | 2.6 | 24 |12 | 64 | | .007 Cream of corn |2/3 ordin. serv. | 3.1 | 11 |58 | 31 | | .02 Vegetable soup |1/2 ordin. serv. | 2.4 | 8 |89 | 3 | | .01 Cod fish (fresh) |ordin. serv. | 5 | 95 | 5 | 0 | .12 | .04 Salmon (canned) |small serv. | 1.75 | 45 |55 | 0 | .22 | .03 Chicken |1/2 large serv. | 1.75 | 39 |56 | 5 | .22 | .05 Veal cutlet |2/3 large serv. | 2.4 | 54 |46 | 0 | .28 | .045 Beef, corned |1/2 large serv. | 1.0 | 15 |85 | 0 | .16 | .01 Beef, sirloin | small serv. | 1.6 | 33 |67 | 0 | .34 | .04 Beef, round | small serv. | 1.8 | 39 |61 | 0 | .24 | .025 Ham, lean | ordin. serv. | 1.1 | 28 |72 | 0 | .22 | .015 Lamb chops |1/2 ordin. serv. | 1.0 | 24 |76 | 0 | .20 | .013 Mutton, leg | ordin. serv. | 1.2 | 35 |65 | 0 | .20 | .015 Eggs, boiled |1 large egg | 2.1 | 32 |68 | 0 |.30 doz.| .025 Eggs, scrambled |1-1/3 ordin. serv.| 2.5 | 37 |58 | 5 |.30 doz.| .03 Beans, baked | side dish | 2.66 | 21 |18 | 61 | .08 | .013 Potatoes, mashed | ordin. serv. | 3.2 | 10 |25 | 65 | .02 | .005 Macaroni |1/3 large serv. | .95 | 15 | 3 | 82 | .10 | .01 Potato salad | ordin. serv. | 2.25 | 10 |57 | 33 | .20 | .025 Tomatoes, sliced |4 large serv. |15. | 15 |16 | 69 | .10 | .10 Rolls, plain |1 large roll | 1.2 | 12 | 7 | 81 |.10 doz.| .01 Butter | ordin. pat | .44 | 5 |99.5| | .35 | .01 Wheat bread |1 small slice | .96 | 15 | 5 | 80 | .07 | .005 Chocolate cake |1/2 ord. sq. piece| .98 | 7 |22 | 71 | .32 | .02 Gingerbread |1/2 ord. sq. piece| .96 | 6 |23 | 71 | .16 | .01 Custard pudding | ordin. serv. | 3.25 | 18 |42 | 40 | .15 | .03 Rice pudding | very small serv.| 2.65 | 8 |13 | 79 | .13 | .02 Apple pie |1/3 piece | 1.3 | 5 |32 | 63 | | .013 Cheese, American |1-1/2 cu. in. | .77 | 25 |73 | 2 | .19 | .01 Crackers (soda) |2 crackers | .9 | 10 |20 | 70 | .10 | .007 Currant jelly |2 heap. spoons | 1.1 | 2 | 0 | 98 | .40 | .025 Sugar |3 teaspoons | .86 | 0 | 0 | 100 | .06 | .003 Milk as bought | small glass | 4.9 | 19 |52 | 29 | .05 | .015 Milk, cond., sweet|4 teaspoons | 1.06 | 10 |23 | 67 | | .01 Oranges |1 large one | 9.4 | 6 | 3 | 91 | | .025 Peanuts |13 double ones | .62 | 20 |63 | 17 | | .004 Almonds, shelled |8-15 | .53 | 13 |77 | 10 | | .025 ============================================================================

From the preceding table plan a well-balanced and cheap dietary for one day for a family of five, two adults and three children. Make a second dietary for the same time and same number of people which shall give approximately the same amount of tissue and energy producing food from more expensive materials.

Food Waste in the Kitchen.--Much loss occurs in the improper cooking of foods. Meats especially, when overdone, lose much of their flavor and are far less easily digested than when they are cooked rare. The chief reasons for cooking meats are that the muscle fibers may be loosened and softened, and that the bacteria or other parasites in the meat may be killed by the heat. The common method of frying makes foods less digestible. Stewing is an economical as well as healthful method. A good way to prepare meat, either for stew or soup, is to place the meat, cut in small pieces, in cold water, and allow it to simmer for several hours. Rapid boiling toughens the muscle fibers by the too rapid coagulation of the albuminous matter in them, just as the white of egg becomes tough when boiled too long. Boiling and roasting are excellent methods of cooking meat. In order to prevent the loss of the nutrients in roasting, it is well to baste the meat frequently; thus a crust is formed on the outer surface of the meat, which prevents the escape of the juices from the inside.

Vegetables are cooked in order that the cells containing starch grains may be burst open, thus allowing the starch to be more easily attacked by the digestive fluids. Inasmuch as water may dissolve out nutrients from vegetable tissues, it is best to boil them rapidly in a small amount of water. This gives less time for the solvent action to take place. Vegetables should be cooked with the outer skin left on when it is possible.

Adulterations in Foods.--The addition of some cheaper substance to a food, or the subtraction of some valuable substance from a food, with the view to cheating the purchaser, is known as _adulteration_. Many foods which are artificially manufactured have been adulterated to such an extent as to be almost unfit for food, or even harmful. One of the commonest adulterations is the substitution of grape sugar (glucose) for cane sugar. Glucose, however, is not a harmful adulterant. It is used largely in candy making. Flour and other cereal foods are sometimes adulterated with some cheap substitutes, as bran or sawdust. Alum is sometimes added to make flour whiter. Probably the food which suffers most from adulteration is milk, as water can be added without the average person being the wiser. By means of an inexpensive instrument known as a _lactometer_, this cheat may easily be detected. In most cities, the milk supply is carefully safeguarded, because of the danger of spreading typhoid fever from impure milk (see Chapter XX). Before the pure food law was passed in 1906, milk was frequently adulterated with substances like formalin to make it keep sweet longer. Such preservatives are harmful, and it is now against the law to add anything whatever to milk.

Coffee, cocoa, and spices are subject to great adulteration; cottonseed oil is often substituted for olive oil; butter is too frequently artificial; while honey, sirups of various kinds, cider and vinegar, have all been found to be either artificially made from cheaper substitutes or to contain such substitutes.

Pure Food Laws.--Thanks to the National Pure Food and Drug Law passed by Congress in 1906, and to the activity of various city and state boards of health, the opportunity to pass adulterated foods on the public is greatly lessened. This law compels manufacturers of foods or medicines to state the composition of their products on the labels placed on the jars or bottles. So if a person reads the label he can determine exactly what he is getting for his money.

Impure Water.--Great danger comes from drinking impure water. This subject has already been discussed under Bacteria, where it was seen that the spread of typhoid fever in particular is due to a contaminated water supply. As citizens, we must aid all legislation that will safeguard the water used by our towns and cities. Boiling water for ten minutes or longer will render it safe from all organic impurities.

Stimulants.--We have learned that food is anything that supplies building material or releases energy in the body; but some materials used by man, presumably as food, do not come under this head. Such are tea and coffee. When taken in moderate quantities, _they produce a temporary increase in the vital activities_ of the person taking them. This is said to be a stimulation; and material taken into the digestive tract, producing this, is called a _stimulant_. In moderation, tea and coffee appear to be harmless. Some people, however, cannot use either without ill effects, even in small quantity. It is the _habit_ formed of relying upon the stimulus given by tea or coffee that makes them a danger to man. Cocoa and chocolate, although both contain a stimulant, are in addition good foods, having from 12 per cent to 21 per cent of protein, from 29 per cent to 48 per cent fat, and over 30 per cent carbohydrate in their composition.