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If the processes of digestion seem complex and but little understood the processes of nutrition are much more so. While nutrition is claimed to be purely chemical, it is acknowledged, by even the most materialistic, to be different in many ways from the other chemical processes known to us. This is particularly true of the final stages of the process by which the pabulum is transformed into living tissue. By this final act dead matter is raised to the plane of living matter.
Even Prof. Chittenden was forced to acknowledge that this "involves a chemical alteration or change akin to that of bringing the dead to life"; while Dr. Charlton Bastian, F.R.S., London, argued that these facts of nutrition, particularly those of the plant, in which inorganic matter is converted into the organic substances of the plant, prove to us the possibility of the creation of life from non-living. All of which shows, that, while the digestion of food materials and their conversion into living tissues is considered to be purely chemical, these are far different from any chemical actions and reactions known to the laboratory, even though the chemist may be able to discover no difference. It cannot be disputed that if the substances are the same and the processes and changes are identical the products would be, to say the least, very similar. But no chemist can even imitate the work done by plant and animal nutrition. The great mystery of nutrition is still unexplained. We can no more explain today how food material is changed into living human flesh and blood than could the lowest savage of a thousand years ago.
It is certain, however that many of the changes the food undergoes after being absorbed are due to the action of enzymes. For example there is autolytic acids, found in the tissues generally, which split the amino-acids, into simpler compounds. Then there are guanase found in the thymus, adrenals and pancreas, which changes guanin to zanthin; adenase found in the pancreas, liver, lungs, muscles, etc., which causes oxidation, as of hypozanthin to xanthin, and of xanthin to uric acid. No effort will be made at this place to take these matters up in detail. The reader who may be interested in pursuing these still further is referred to any of the standard works on nutrition. We must devote our attention to the use of foods.
Let us begin with the proteins, since these have been the subject of more discussion than any other part of our food, and are considered, by "orthodox" scientists, to be the most important of all elements of our food. All this came about as a result of the mistakes of the early physiological chemists, particularly Liebig and Vogt of Germany. These found that muscle is almost pure protein and water and Liebig thought we should eat muscle to make muscle. Of course, the cow eats grass not muscle, out of which she makes the muscle Liebig would have us eat, but this simple fact was overlooked.
Voight followed Liebig with a series of experiments on dogs. This was about 1860. With these he thought he had succeeded in proving the great physiological importance of protein. It was assumed that muscular activity is due to the oxidation of the cells themselves. It was a case of mistaking the "machine" for the "fuel;" yet, on the basis of this assumption Voight, with the aid of his dogs, estimated that the average man requires about 118 grams of protein daily. He seems later to have reduced this standard by nearly one half, but no one took the reduction seriously.
The Voight standard is now known to be much too high. Protein leaves the body through the kidneys in the form of urea. In fact, the composition of the urine depends more upon the protein (nitrogen) intake than upon anything else. By measuring the excretions and comparing these with the food consumed, it is possible to tell whether less protein or more protein is being lost than is being consumed. Examinations of the urine under almost all conceivable conditions of life and activity, have shown that in the healthy adult the nitrogen intake and output is balanced, providing, of course, the intake is not less than the actual needs of the body.
No matter how much nitrogen one consumes above the body's requirements, the organism always responds in the same way. That is, it sets aside for excretion, all surplus nitrogen. So unless the nitrogen intake is less than the body's requirements, the balance is usually struck between income and outgo. Exceptions to this are during growth, following a protracted fast, convalescence after wasting illness, and pregnancy and lactation, during which periods the body excretes less nitrogen than is consumed; and during some diseases in which there is a rapid breaking down of tissue and consequently more nitrogen is excreted than is consumed.
The body does possess the ability to store protein although compared with its ability to store carbohydrates and fats, this ability is very limited. Surplus nitrogen is carried in the blood at all times.
For growth and reproduction, larger quantities of protein are, of course, requisite, and it is even more desirable in that case that the proteins should be of high biological value. In growing children and youths the protein requirements exceed that of the adult by 50% to 100%. Pregnant and nursing women require considerably more protein than adult males or adult non-pregnant and non-lactating women.
Repeated examinations of the urine have disclosed the fact that the proportions and quantities of the urinary constituents are modified by exercise or physical labor very little. This means that protein decomposition is not materially increased by physical effort and leads to the conclusion that the protein requirements of the average healthy man or woman are no greater, while engaged in manual labor, than while engaged in mental effort.
For years the "orthodox" scientific world held tenaciously to the high protein standard set by Voight. Although Hershfeld had, in 1887, by a series of tests, placed the protein standard at 47 grams, the orthodox chemists never accepted his standard and the low protein diet did not attract much attention until Horace Fletcher startled the scientists out of their lethargy some years ago. Since then, much evidence has been accumulated by the progressive members of the scientific world, showing that protein is not so valuable as formerly supposed. In fact, the evidence is strongly in favor of the statement that protein--and certainly excessive protein--is a physiological burden and destroys health.
The experiments of Hirshfeld have already been referred to. He was a young man of 24 years and performed heavy labor, weight lifting, mountain climbing, etc., on a diet containing less than half the protein that was thought to be necessary. He lost neither weight nor strength, while the "nitrogen balance" showed that he did not lose body protein. Dr. Hindhede says of his work: "It is strange, indeed, that Hirshfeld's investigations have been allowed by science to drift almost into oblivion. He was a young man (twenty-four) who could make little impression against the weight of Voight's authority."
In 1913 Berg pointed out that when the conditions are in other respects optimal, the amount of protein requisite to maintain body-weight is far smaller than hitherto has been supposed. Boyd, in America, using meats as the source of protein, estimated the minimal daily amount of protein requisite to maintain body weight as 30 grammes. Berg under more accurately adjusted conditions estimated the requirements to be 26 grammes of meat protein. Rose, providing a better supply of alkalies, found the meat protein minimum to be 24 grammes. Sherman places the requirements at 30 to 50 grammes.
Hindhede raised four athletic and wide-awake children on a diet so low in protein that it has been said, "it would frighten a cooking school teacher into blind staggers." He has proved that a high protein diet is not required by growing children.
But this was not the end. Hindhede found that the excess proteins, after entering the blood, underwent decomposition and recomposition giving as a result nitric acid, phosphoric acid and sulphuric acid. There was also an excess of uric acid and ammonia compounds. He contended that in order to neutralize the acids formed by the decomposition of excess protein, the body was forced to give up its mineral salts. Thus the teeth, bones, cartilages, nails, hair, etc., were leeched of these elements.
These powerful acids destroy the liver and kidneys to such an extent that one may safely say, no man ever died of uremia whose kidneys had not been, for years, gradually destroyed by the powerful acids resulting from excessive protein intake.
It was long thought that muscular tissues are oxidized or decomposed in the development of muscular power and that they are rebuilt from food, particularly protein. This, if true, would have given rise to even larger protein requirements than the standards called for. Anyway, during these years we have been feeding upon beef steaks, eggs and other high protein foods, all the while claiming that we did not want to suffer from malnutrition and become lean, pale, individuals like the vegetarians, nor did we want to rear dwarfed offspring like the rice-eating Japs and Chinese.
The life insurance companies have discovered that the lean folks (the skinny) live about twenty years longer than they should. Every schoolboy knows that the Japanese Jenrikska men pull beef-fed Englishmen through the hills and mountains of Japan at the rate of about forty miles a day. Several years ago a seventy-mile walking race was staged in Germany. There were eight vegetarians and fifteen meat eaters. The first six men in were vegetarians. Most of the meat eaters never finished the race. Dr. Hindhede says: "A diet low in albumen increases endurance. I have never heard of a great meat eater winning a long distance race."
That the protein requirements of growing animals is not high is shown by the fact that milk, the natural food of young animals, is very low in protein, when compared to meat or eggs. Cow's milk, for example, is about three and one-half per cent protein. The calf is a very active and rapidly growing animal, in fact, of more rapid growth than the human infant. As the calf grows older, it adds grasses to its diet and these are much lower in protein content. The cow will, from grasses alone, secure all the proteins required for her and her calf, both during pregnancy and during the period of lactation.
Milo Hastings says in Physical Culture for March, 1916: "The human youngster grows so slowly, after the first year or two, that the amount of protein needed for growth is so small in proportion to the other elements of the diet needed for heat and energy that the active child eating a diet of cereals, fruits and vegetables in sufficient quantities to keep up childish activity, must of necessity consume more protein than is needed or can be utilized in growth.
"A young pig may gain a pound a day, but a young human rarely gains an ounce a day. In fact it takes him fifteen years to gain a hundred pounds. Eggs are about the same composition as the human body, and if for fifteen years a child ate no protein but that contained in one egg a day he would have eaten six times the protein equivalent of his own body. One sixth of an egg a day supplies the growth protein for the human youngster. On the plan of rearing young America on two pounds of meat, milk, eggs, legumes and cheese and bread a day, which plan our orthodox food chemistry prescribes, the growing child must pass through his liver and kidneys and utterly waste enough protein to build about five thousand pounds of human flesh.
"This thing figured out becomes a farce. The stuffing process of raising children is better suited to make pigs that would gain three hundred pounds of flesh in a year. Nature needs eighteen years of experience to bring a human brain to maturity, and so she provided a trap door through which to dump out the pig diet and keep us human still. How much physiological harm the dumping process works upon the child's organism we do not yet know--probably much less than most of you, after reading these lines, will imagine. The adaptability of our physiological machine is a never ceasing source of wonder."
It is evident that there is no danger of anyone ever consuming too little protein. In fact, this is just what Hindhede found in his studies of the dietetic habits of nations. He found that in the degree to which a nation lived on a low protein diet, in that degree did they suffer less from disease. During World War I, his opportunity came to demonstrate on a large scale, the truth of his findings. He was made food administrator over Denmark. His experiment involved a whole nation of millions of people and covered a period of three years. No other investigator had ever had such an opportunity. He reduced the death rate in Denmark forty per cent in one year's time by diet alone. He employed a low protein diet. He concludes that the average adult human body may require twenty grams of protein daily, but that the requirement may be even less than this. His assistant, Dr. Madsen, used an experimental diet containing but twenty-one grams of protein, with only favorable results.
Both Berg and Abderhalden have shown that the assertion that meat protein is the most valuable of all forms of protein cannot be accepted as a positive fact as regards the protein of individual muscles, but only as regards the aggregate proteins of the animal body used as food. Berg showed that the aggregate protein of eggs, cow's milk and to some extent that also of potatoes, are more efficiently utilized than meat protein. It is only fair to add that in Berg's experiments the meat was given with an excess of acids, whereas, Rose found that when an excess of alkalies is supplied the proteins of meat are approximately as valuable as those of milk.
Turning now to carbohydrates, let us state in a general way their uses in the body. They are used chiefly in the production of heat and energy. At least this is the orthodox theory. Instead of, as formerly held, the muscle cells being consumed in muscular activity, it is now asserted that sugar (glycogen or muscle sugar) is oxidized in the cells giving rise to energy. Fat is an available second choice. The monosaccharides are converted into glycogen in the liver.
The body stores up carbohydrates and does not eliminate all of the excess supply, as is the case with proteins. Some of these are stored in the liver as glycogen, some in the muscles as muscle sugar, while some is converted into fat and stored as such. It is only after this is done that any excess is eliminated.
We hear much of starch poisoning these days. Hindhede found that starch poisoning was seldom, if ever, met with among those people whose diet is predominantly carbohydrate, if they lived on natural instead of denatured starches and sugars. Starch poisoning, by denatured carbohydrates is due to the fact that these have been robbed of their minerals and vitamins and this causes them to leech the tissues of their salts. It also leads to carbohydrate fermentation.
To illustrate what we mean by denatured carbohydrates leeching the tissues of their mineral constituents, let us look for a minute at the process of sugar manufacture. Nature has placed in the natural sweets enough of the organic mineral elements, and water and oxygen, to satisfy their "desire" for these elements. In the process of manufacture of commercial sugar, these other elements are extracted, giving "free" and "unsatisfied" sugar. So great is the affinity of sugar for iron that it must be made in copper kettles, as it abstracts the iron from kettles and literally "eats" holes in them. In the body the denatured starches and sugars do likewise. They leech the tissues of their mineral salts. "Free" sugar also has an almost insatiable "desire" for oxygen and calcium.
Carbohydrate fermentation gives rise to carbon dioxide, alcohol, acetic acid and water and results in chronic auto-intoxication, which resembles, in every way, the symptoms of chronic alcoholism. The alcohol produces chronic irritation in the system and results in the formation of scar tissue. Previous to the formation of the scar tissue there are the usual disturbances caused by irritation. It also causes capillary congestion which result, in turn, in atrophy of brain and muscles. The irritation of the mucous surfaces results in the overproduction of mucous giving rise to catarrh.
Fats follow about the same course in metabolism as carbohydrates. These are oxidized to supply heat and energy.
The body is said to have no method of storing mineral salts as in the case of carbohydrates. Yet a fixed amount is kept suspended in the blood. After a fresh meal, there may be an excess in the blood, but this excess is promptly eliminated. The body can and does conserve and save its minerals when there is a scarcity of these. For example, the iron in the seven million cells that perish every second, from wear, is recovered, stored in the liver and spleen, and used in rebuilding the blood.
Vitamins are not employed as foods, but as aids in assimilating foods. A reserve of these is stored in the liver and other glands, fat, etc.
After foods have been metabolized they are excreted from the body through the lungs, liver, kidneys and the walls of the colon. Each organ of elimination has its own peculiar work to perform although reciprocity is not lacking. Acids are eliminated chiefly by the kidneys and lungs, carbonic acid gas being the principle excretion of the lungs. Alkalies are eliminated through the kidneys and walls of the intestinal canal. Calcium, magnesium and an increased acid-intake results in increased acid-elimination by the kidneys; whereas an increased alkali-intake results in an increased alkali-elimination by the colon. Insignificant quantities of salts and urea are eliminated through the skin.