Abnormal Fermentation

When the digestion of carbohydrates is slow or ceases, bacteria and yeasts give rise to abnormal fermentation. Bacteria are probably always active to some extent in the small intestine, and when carbohydrate food is eaten in quantities so large that it cannot readily be disintegrated by salivary digestion and the muscular activity of the stomach, it is certain to be a nidus for their growth. Potatoes, fried or stewed, and swallowed in chunks, will be slow to disintegrate. Fresh hot breads usually form masses of dough in the stomach that cannot well be broken up. A large meal of pancakes and syrup will be imperfectly prepared by the stomach for digestion, partly for the same reason that hot breads are, and partly because the excess of sugar that is eaten overtaxes the digestive powers of the organs. These articles of food at the temperature of the body, and mingled with the other contents of the stomach, are especially favorable media for the growth of numerous micro-organisms.

The results of bacterial fermentation of starches and sugars are ethyl alcohol, acetic, lactic, butyric, and succinic acids, carbonic acid gas, and hydrogen. Cellulose, when decomposed, forms marsh-gas and carbonic acid gas. The flatulence and meteorism characteristic of many dyspeptic states are due chiefly to the copious generation of these gases. When carbohydrate food rich in cellulose is fermented, it is especially productive of gases. Sugars are more likely to produce an excess of lactic, butyric, and acetic acids and a moderate amount of carbonic acid gas.

Bacterial fermentation usually lessens from the beginning of the small intestine to its end. When excessive, it continues in the colon. Gases in the small intestine give rise to rumbling noises - borborygmi. These gases rarely find their way into the stomach. They may be passed from the anus, or may in part be absorbed.

An idiosyncrasy present in certain persons is an inability to digest much carbohydrate food. Fever lessens the activity of all digestive processes and increases the tendency to abnormal fermentation. Most chronic diseases that produce great weakness have a similar effect.

Absorption

Carbohydrates are absorbed almost exclusively from the small intestine. A very small amount may be taken up by the walls of the stomach and the large intestine. Cane-sugar and milk-sugar are readily absorbable, but must undergo changes before they can enter the blood. Their conversion into dextrose may occur in the epithelial cells or be produced by inver-tase in the succus entericus.

These processes may be interfered with by extensive inflammation of the small intestine and by those maladies that are characterized by frequent profuse watery stools.

Action Of Liver

The blood in the portal vein may contain as much as 0.3 per cent, of dextrose, but the blood that leaves the liver and enters other tissues of the body does not contain more than 0.1 per cent. It is evident, therefore, that much of the carbohydrate food that is eaten is arrested by the liver before it is distributed to the other tissues. The dextrose of the portal vein does not remain in that form in the liver, but is transformed into comparatively insoluble glycogen. Glycogen is derivable to a small extent from fat and proteins, but carbohydrates are its chief, almost its exclusive, source. Sugar is retained in the liver as glycogen only temporarily. The organ contains an amylolytic ferment that converts it again into dextrose, in which form it is found in the general circulation. Glycogen is also formed and stored to a limited extent in muscles.

Utility

Dextrose is utilized by the metabolic tissues for the liberation of energy. Whether this is accomplished in the blood or in the lymph when it is in contact with active cells, or whether it must first be absorbed by, or form part of, the cells, has not yet been established though most physiologists to-day believe that it is accomplished outside the cells by a ferment which is made active by something derived from the pancreas. When metabolized, the waste is eliminated chiefly by the lungs as carbonic acid gas and water.

All the dextrose in the general circulation is not used for the creation of energy; a part of it is stored as fat in the connective tissues. It is put away, as it were, as a reserve of potential energy.

Pavy contends that many protein molecules contain a carbohydrate element, and that albuminoid matter can be split into protein and carbohydrate matter or, it may be said, better into a nitrogenous and nonnitrogenous portion. This takes place apparently when, in certain diabetics, the ingestion of food has ceased, glycogen has been consumed, and still sugar is excreted. He claims that from 45 to 60 per cent, of the protein molecules is thus transformed into sugar. Not only can albuminoids be decomposed into protein and carbohydrate elements, but also a synthesis can be effected and part of the ingested and absorbed carbohydrate goes to form protein molecules.

In diabetes there is a disturbance of dextrose metabolism that permits it to accumulate in the general circulation until it exceeds the normal 0.1 per cent., when it is eliminated by the kidneys. Individuals are peculiar as to the ease with which they store dextrose as fat. There are many who accumulate fat even upon a poor diet, and many who remain thin upon a habitually generous one. These variations become pathologic in cases of obesity and of excessive emaciation. Emaciation does not necessarily mean an inability to form fat from carbohydrates. The fault lies often in the digestive organs, where food is not properly prepared for absorption or is not retained; or the dextrose that is absorbed is consumed in the production of heat, as in fevers.

Interrelationship Of Foods

The interrelationship of proteins, fats, and carbohydrates is well illustrated by the following diagram. The ability of each to replace measurably one or both of the others is also shown. When proteins are eaten they are in part transformed into tissue, in part directly catabolized, and in small part transformed into carbohydrate matter and fat. When fats are eaten they are in small part stored in the tissues as fat; in large part they undergo combustion directly. A part of the stored fat of the system that may be consumed in case of need is derived from the proteins and carbohydrates. Carbohydrates for the most part undergo direct combustion.

Physiologic Interrelationship Of Foodstuffs

It is evident from this that proteins can very imperfectly replace the functions of fat and carbohydrate. Fat and carbohydrate are closely related in function and may in large degree replace each other, but neither can perform the special functions of proteins.

Vegetarianism

Those who live chiefly upon cereals, vegetables, fruits, and nuts are called vegetarians. These foods are with rare exceptions supplemented by such animal food as milk, cheese, and eggs. A menu made up of these foods can be so planned as to supply both the carbohydrates, fats, and proteins that are needed. A part of the protein is derived from milk and eggs, and a part from the vegetables eaten. The nitrogenous matter obtained from vegetables is less easily digested than that which is of animal origin; a much larger percentage passes from the alimentary tract unutilized. Few persons live entirely upon a vegetable diet. Those who attempt it lose vigor and show languor and disinclination for physical and mental work. They become less able to resist disease. Because a vegetable diet is an economical one, it has sometimes been forced upon bodies of laborers, but uniformly the decrease in the amount of work that they are able to perform more than counterbalances the decreased expense of their food.

In vegetables enough protein can be found to make it possible to substitute them for meat for the purpose of maintaining life and strength. As vegetable protein is very imperfectly digested and absorbed, a sufficient vegetable diet must be a very bulky one. It will maintain strength, and by eating vegetable food only one may be able to lift as much; but one will not be able to work so fast as on a mixed diet. He will lack energy and alertness.

It is quite evident, from man's anatomic structure, physiologic functions, and habits of eating, handed down from the earliest times, that a mixed diet is best adapted to his needs. At the same time it is unquestionably true that too much meat is ordinarily eaten by many individuals.

Effect Of Changes Of Diet

Often a change from a generous mixed diet to a so-called vegetarian regimen improves the health of individuals. It does this chiefly by correcting bad habits, such as eating too much, eating rich foods, drinking little; and by removing such pathologic states as constipation. A radical dietetic change usually diminishes a person's appetite, for fewer things that he enjoys are placed before him. The vegetables, fruits, and cooked cereals contain a larger amount of water than may otherwise be obtained. The coarser cereals, such as bran bread and fruits, as well as the increased supply of water, help to provoke more regular and copious bowel movements.