Nutrition - Protein
( Originally Published 1954 )
Nearly every food used by man or animal contains some amount of protein. The percentage of protein is relatively high in those that are classed as proteid foods. Those foods contain between 15 and 30 per cent of protein.
Grains contain about 10 per cent on the average. Milk contains about 4 per cent; fruits and non-starchy vegetables contain about 1 to 5 per cent protein.
The basic elements in the composition of every protein are oxygen, hydrogen, carbon, nitrogen, and sulphur.
In the case of fats and carbohydrates, only three elements-carbon, hydrogen and oxygen—are essential to their chemical make-up. Protein is more complex than carbohydrates or fats, and the nitrogen and sulphur in its makeup account for this greater complexity, chemical and vital. The chief functions of protein in nutrition are:
(1) Protein is essential for the structural makeup of plant and animal cells.
(2) Protein is needed to supply materials for the growth of new tissue, and
(3) For the replacement of materials of the body cells worn out as a result of their organic activities.
Proteins, like fats and carbohydrates, are produced in plants from the elements of the soil and air. The animal body resynthesizes vegetable proteins into its own characteristic tissue proteins, even though certain species (carnivorous) can also utilize proteins of other animals for the same purpose.
However, animal proteins are not superior or essential; and they are even disease-causing in the human body.
The digestive juices of the stomach and intestines act upon proteins, reducing them to simpler products called amino acids. In the amino acid stage, proteins are absorbed into the blood for systemic nutritive purposes.
Every kind of protein yields, after digestion, sixteen to twenty different amino acids, each of which has specific functions to perform.
Some of the amino acids are necessary for cellular and tissue growth. Others are necessary for the structure and functions of muscles. Certain others contribute to the formation of carbohydrates (dextrose) within the body.
Still other amino acids aid in the chemical processes of the body whereby certain of its wastes are neutralized, or made harmless, and excreted from the body. Other amino acids are necessary to maintain the skin and its appendages, the nails and hair, in health. Certain amino acids are needed for bone and cartilage.
Some of the amino acids have the power of changing into others which may be more in demand by the tissues and fluids of the body. Certain amino acids cannot be remanufactured from others in the body; they must be supplied by the food proteins.
Because of their especially vital importance to the body, two such essential amino acids, lysine and tryptophan, will be discussed in detail- Some important and illuminating facts are now known about these two amino acids-thanks to modern researches in nutrition.
Casein, the principal protein of milk, consists 7.62 per cent of the amino acid, lysine. The cereal protein zein (corn) and gliadin (rye) contain an insignificant amount of lysine. In nutritional experiments, animals are found to require lysine for the growth of the young. Those fed on protein lacking or deficient in lysine failed to grow. When lysine is added to such deficient foods, growth is soon increased. The animal proteins, as is shown, contain more of this amino acid than the cereal proteins, but gelatin as well as milk are products of herbivorous animals.
Feeding experiments by E. V. McCollum, H. C. Sherman, and others show that the proteins of green leafy vegetables, apples, soy beans, Brazil nuts, and other nuts possess the proper amount of lysine necessary for healthy normal growth.
The amino acid tryptophan is found necessary to maintain the body in protein balance. When food protein-deficient or lacking in tryptophan is fed to the growing or mature individual, such food fails to replace worn-out materials which are lost by the body during the organic activities of its cells, tissues and organs. The amino acid tryptophan is used up in the vital activities of the body, and it must be replaced to prevent atrophy of the body's structures.
The protein foods containing relatively much tryptophan are those which are particularly rich in sulphur. Eggs, nuts, beans, and peas contain relatively more tryptophan than other proteins which contain a lower percentage of sulphur.
However, the eating of more tryptophan-containing foods than the body requires tends to favor intestinal putrefaction. The body needs less of this amino acid than is supplied in any dietary by people anywhere in the world where the dry legumes, meats, fish and eggs are protein staples. When, because of a shortage of lysine and tryptophan-containing foods, people must subsist on cereals and on root and tuber vegetables, relative starvation may result because these foods are deficient in the amino acids promoting growth and maintenance.
Controlled experiments in the laboratory made clear these important facts about nutrition. Thanks to the New Knowledge of Nutrition, there need be no detrimental results in the dietaries of mankind. Some nutritionally good proteins of plant origin may supplement a cereal-vegetable dietary to obviate disastrous nutritional effects.
All foods contain protein. The body needs a comparatively small amount of concentrated proteid food, properly selected in quality, in order to attain successful body nutrition.
When protein, or nitrogen-sulphur-containing food, is eaten in excess of the body's needs, putrefaction of the surplus takes place in the colon. Poisonous gases are formed as a result of such disintegration. Some of the gases so generated indicate their nature by their smells and by their names, for example, "putresin," "cadaverin," etc.
A portion of such poisonous gases may be expelled from the colon via the rectum. Another portion absorbs into the blood through the wall of the intestines. Such poisonous gases do not have any good effect on the system. Chronic disease in many forms may be found in people whose colons are chronically stagnant cesspools because of excessive protein eating. Those having colons habitually free from foul gases avoid a most important cause of disease. Those who are ailing and want to get well must start with a cleansing regimen of the colon, and must avoid or restrict the use of proteins that are high in sulphur content.
The liver and kidneys get overloaded by excessive protein eating, because these organs must do the work of disposing of the excess amounts of absorbed protein in the form of waste matter. One of the functions of the liver is to convert protein into urea, which the body economy rejects. Urea is a protein waste product of metabolism. (Metabolism is the chemical process which foods undergo in the body, from the stage when digestion ends to the stage when its waste products are ready for elimination.)
The kidneys eliminate urea as one of the normal urinary waste constituents. The amount of urea excreted depends on the amount of protein eaten and also on the efficiency of kidney functioning. According to Folin, a scientific investigator of protein metabolism, most of the protein which people eat never even enters the general blood-stream! It is carried from the digestive system into the liver directly, where it is converted into urea.
It is a physiological fact that the general blood-stream has the selective power of accepting nutriments from the liver only when there is a constitutional demand for them. When the liver is sup-plied with protein beyond constitutional needs, it may dispose of the excess by sending it as waste to the kidneys; or it must store it within its own boundaries and send a certain amount into the blood of the entire body. The blood in turn sends it to the lymph and to the cells.
With the constant milling of food in the digestive tract, the liver is obliged to keep its portal (portal vein) open to receive nutritive pabulum, but the general circulatory system (the blood and lymph) cannot always accommodate as much nutriment as the liver may be able to supply. The presence of excess anywhere in the body slows down every organ in its functions, and it has been conclusively proved that the alimentary organs nearly always do excessive labors, thus influencing other branches of the body economy in their functions.
The cells of the tissues and organs cannot throw off their wastes readily when the blood and lymph carry more food materials than they can accommodate.
That the human body is wasteful has often been emphasized by scientific observers. Proteins eaten in excess of the body's needs con-tribute in no small measure to this wastefulness. Yet, in spite of all the scientific data available on this subject, conventionally accepted health authorities, when asked for advice on diet, often prescribe eating to the point of gorging and nausea.
There still exist false concepts with regard to protein requirements. For example, the consensus of opinion even with regard to child feeding is that every child needs fish, meat, and eggs on the daily menu, in addition to "a quart of milk" a day. As a matter of fact, some children are even emaciated despite all kinds of proteins on their daily bills of fare. Others may grow robust. Those in the latter category have vigorous digestive and assimilative powers. The weak and under-nourished children, or those below par, should be fed only as much protein as they can physiologically handle, that is, not sufficient to force excessive labor on the stomach and intestines, causing putrefaction from incompletely digested and unabsorbed protein.
It may be observed that the thin, stunted individual (child or adult) is also anemic and the same individual has often a veritable cesspool within his colon. The underweight person is an ailing individual in most cases. His digestive power is not as vigorous as that of an individual who is strong and well. Yet overfeeding is encouraged very often by the learned physicians and surgeons and frequently in spite of the protests of the diseased victims.
Those in good health who eat liberally of protein may not show any pronounced immediate ill effects, but they are building up to disease nevertheless. This statement cannot be disputed in view of the appalling health situation among middle-aged people.
That protein consumption in excess of the organic needs of the body (including three "square" meals per day) makes for disease is a fact definitely proved in clinical experience with the sick. The road to recovery is cleared to a great extent when protein intake is reduced for a certain period of time, or is entirely eliminated from the diet for a few days or longer, as individual indications may warrant.
The term protein, as applied here, refers mainly to the concentrated varieties. Valuable laboratory studies on the problem of the daily protein ration have been conducted by various university nutritionists all over the world, and the truths discovered in this field are exceedingly interesting and of practical value in planning for the food needs of individuals and groups.
In dietetic laboratory studies on human subjects, conducted by various scientists to determine the amount of protein which is sufficient to keep the body in nutritional balance, different students of the problem arrived at a similar conclusion: namely, the body needs less proteid food than people habitually include in their daily dietaries- The amount of protein found in one or two eggs, or in an ounce of cheese, or in an equal amount of beans or nuts, is sufficient for the adult or child.
Some advanced European students of nutrition arrived at similar conclusions.
A well-known Japanese physiologist, Kumagava, determined that an average of 54 grams, or less than two ounces per day, of concentrated protein food is needed by the adult human body.
Klemperer, another noted investigator, also studied this problem. In an experimental study with two young men, weighing respectively 141 and 144 pounds, he determined that less than one ounce of concentrated protein food daily was necessary to maintain them in normal health and weightl
An eminent German physiologist, Voit, established a standard requirement of 118 grams of protein, or about four ounces per day.
Another nutritionist, Atwater, studied the dietaries of twelve hundred people. They used 100 to 175 grams of protein a day per person.
Folin, a well-known biochemist, showed that only a small amount of the protein eaten is assimilated. Most of the digested protein goes to the liver where it is transformed into urea and other waste products, to be thrown off by the kidneys—if the kidneys are able to throw off all such wastes.
A prominent authority worked out a formula by which one may determine protein requirements in relation to the weight of the individual. According to his researches, one-third of a gram of protein per pound of body weight is required daily.
This is a dangerous formula because overweight individuals cannot handle proteins physiologically; they do not need so much as light-weight individuals. Lightweight individuals have more strength to work. They therefore are able to burn up more protein. Over-weight individuals, as a rule, suffer from physiological inadequacies such as shortness of breath and the tired feeling, because their vital organs (the heart and breathing mechanism) are affected by fatty infiltration.
The high protein rations suggested by the various authorities mentioned above are not only unsafe but dangerous, when applied to individuals who are past forty or fifty years of age. Young people, lean or fat, are able to handle various standardized high protein rations with more body comfort than older people.
A standardized protein ration is therefore not to be recommended as a general rule. Any stereotyped plan, when put into practice, would fail because digestive and assimilative powers differ not only with different individuals but also with the same individual under different conditions. Strain of any kind will reduce the power of the body to properly chemicalize food in general and protein in particular.
The proper guide for protein intake is: physical and mental comfort and well-being. Under normal conditions one may eat any amount of protein desired, providing it does not produce any ill effects such as foul gases, fatigue, or constipation. Protein must be properly combined with other foods that are eaten at the same meal. Correct food combinations are the only logical basis for the daily choice of protein or other heavy staples. A green raw salad or fruit, or both, should accompany every protein meal. Other foods such as bread and potatoes, if eaten at the same meal with protein, should be taken in very small amounts.
Any individual can verify these truths in practical problems with the feeding of the well or sick. A pioneer here and there departs from the age-old empiricism of overeating in health or in disease. Today these pioneers are ill understood. Many a standard bearer of the truth was not readily accepted in the past. The history of human progress has seen many stumbling blocks because of the stubbornness of the human brain.
How are the underweight going to build up their body deficiencies in protein? By rest and conservation of energy, and by eating only that which allows physical comfort.
Certain people who enjoy excellent health and a high degree of physical and mental efficiency may be observed to be small eaters- In general they consume a very small amount of protein. The conventional habit of consuming amounts of protein in excess of the body's needs is a wasteful way of overworking the digestive and eliminative organs and undermining the well-being of the body. This truth is proved by the relief and benefits which come from lighter eating in general and from eating less protein in particular.
The study of food products in relation to animal and human nutrition has been of help in arriving at a definite understanding of proteins, and their biological values to the body. A simple grouping of food proteins is as follows:
(1) GOOD-protein of milk, eggs, nuts, soy beans, and the protein of green leafy vegetables.
Good proteins are complete proteins containing the essential amino acids in ideal proportion to support growth and nutritional maintenance for normal organic and functional needs.
(2) INTERMEDIATE-Proteins of root vegetables, tubers, cereals.
These proteins in the intermediate class may be sufficient for maintaining the body in fair functional condition, but cannot supply enough material for the growth of the young.
(3) POOR-protein of dry legumes such as beans, peas, lentils.
The proteins of dry legumes are classed as poor in biological value because of their deficiency in essential amino acids to the ex-tent that they can neither promote growth nor maintenance if they are the only sources of protein. However, with an adequate amount of biologically good proteid foods, the mixture will be balanced for normal nutritional needs. This principle is worth bearing in mind because foods like the vegetable roots and tubers, beans, peas, and lentils, are very valuable for their carbohydrate and mineral content. Their proteins may be utilized by the body to a considerable extent, but they must be supplemented by protein especially rich in the amino acid lysine. The addition of a liberal amount of green salad material daily, and a few nuts or an egg, or some milk, to foods in the "intermediate" and "poor" categories would produce an ideal protein mixture for proper nutrition of child and adult.
Milk as a protein is of very high biological value. It contains the growth-promoting amino acid lysine in very large amounts.
Its protein is easily digested and assimilated. The organic minerals of milk, particularly calcium and phosphorus, are worth noting, especially in cases where malnutrition exists. In fact, dairy products, such as milk and fresh farmer cheese or cottage cheese, are the best to restore good health to the nutritionally subnormal in weight and strength.
The egg is potentially an animal being. It therefore contains adequate protein for building new tissues of every kind in the body.
The albumen, or white of the egg, is a typical complete protein of good biological quality. The yolk is a superlative protein, being extremely rich in iron compounds and certain fatty protein which are of great value in blood and nerve building. However, the sulphur content of both yolk and white is comparatively very high, and any excess of sulphur-containing food causes poisonous gas formation in the intestines of those who are limited in digestive and assimilative strength.
If eggs are used at all in a diet, they should be included in occasional meals only and not used daily.
Eggs, like meat, are not essential in the human diet. A correct choice of plant foods can make a more ideal protein mixture of good biological value for healthful nutrition of the body.
The tissues of dead animals decompose even under refrigeration, giving rise to poisonous chemicals and micro-organisms. One of the objects of cooking and seasoning meat is to make it comparatively safe for the human digestive system and general health. However, meat products are never made completely innocuous to the human body. One reason is that they readily decompose in the digestive tract. Proteins of vegetable origin and fresh milk protein are much safer for human digestion and assimilation.
Milk and vegetable proteins do not decompose or putrefy as readily if they remain in the intestinal tract because of delayed digestion or absorption. Meats or fish, when insufficiently digested or absorbed by the blood, readily disintegrate into deleterious products in the small intestine and colon.
Since all foods contain some protein, and the human body needs a very small amount of concentrated protein, it is important to decide how to use this essential nutriment for efficient body economy.
The three-meal-a-day plan evolved by custom and supported by scientific opinion is fair enough for most people. However, this rule must be flexible, as some individuals can thrive better on two meals, while others may get along on one, and still others may need food four or five times a day. Whatever the number of meals, the essential amount of protein for maintenance of normal health and weight must be supplied to the adult. And in the feeding of growing individuals, the factor of growth promotion must be considered in arranging meals.
The easily digestible proteins, such as fresh milk, cheese, etc., are excellent for children.
Fruits combine well with milk at the same meal. The breakfast for adults needs no protein. Adults will enjoy better health if breakfast is very light, consisting of little more than water and fruit juice.
This is especially true of those who wake up tired and weak-limbed in the morning. In other words, adults who are suffering from retained tissue cellular catabolic poisons should avoid taxing the body with complex protein food in the morning. Fresh air, water, and the vitamins of fruit juice are needed to cleanse the body cells and tissues.
During the active part of the day (at noon), it is best to eat the energy-producing foods—carbohydrates. In cool weather, certain fats can be utilized by the body as sources of energy. These foods are more readily metabolized by the system than is protein. The latter takes longer to digest. Therefore, it is best to take protein—that is, decidedly proteid food—at the evening meal when the body is more at rest. The digestive process goes on more ideally during rest. The best foods for combination with concentrated protein are raw salads, fruits, and steamed vegetables.
Bread, potatoes, or other starches should not be eaten at the same meal with protein. The universally accepted "scientific" health authorities pooh-pooh the idea of separating starchy food from protein at meals. The real truth is that supposedly scientifically "balanced" meals which include protein, starch, fat, stimulants, and condiments are merely hodge-podge and haphazard mixtures of incompatible elements, good for nothing but disease building.
Simplification of the menus of the day is in harmony with the natural requirements of the body and in harmony with health-building principles. From this standpoint alone it is convincing enough that as little concentrated protein food as possible should be eaten with other foods that are heavy and difficult to digest. Furthermore, people today are almost always depleted in energy. They need reserve energy for other labor besides digestion. Therefore meals should be simple and only one concentrated food should be eaten at any meal.
The chemical argument against eating starch and protein at the same meal, as advanced by Dr. J. H. Tilden, does not seem quite correct or scientific. According to this theory, starch requires an alkaline medium for digestion, and protein requires an acid medium. Yet it is a fact that protein starts its digestion in the stomach where the digestive secretion is acid in chemical reaction, and its digestion is completed in the small intestine where the medium is strongly alkaline. The same is true with regard to starch digestion: namely, some progress in carbohydrate digestion is made in the stomach, and then the digestion of carbohydrates (starch particularly) is completed in the small intestine in an alkaline medium.
Digestion of any food depends on chemical activators called enzymes. The stomach has no enzymes to act on starch. Saliva, however, has such enzymes, and if starch is properly ensalivated by sufficient chewing, its digestion continues in the stomach. When starch is eaten alone there is not as much active secretion from the digestive glands of the stomach as when it is eaten with protein, for the latter has a specific stimulating effect on the digestive glands of the stomach.
What does happen in the stomach to impair the chemical reaction when protein and starch are eaten together at the same meal, is that the starch mechanically absorbs the pepsin. Pepsin is an enzyme or chemical activator needed for protein digestion (Kellogg). When it is thus wasted, protein digestion in the stomach is consequently inefficient.
With so many "dyspepsia" sufferers in the world, the habit of mixing decidedly proteid food with decidedly starchy food at the same meal should be discontinued. Eating only a few different foods at each meal is the dictate of nature and the best service to the body.