Dietetics for Nurses

by Fairfax T. Proudfit

Types of Bacteria.—It would be impossible and unnecessary to consider the action of all of the bacteria in the body in this text, but it is necessary to consider those which are prominent in bringing about decomposition of the foods in the digestive tract. Sherman holds that there are three main types having this property: “(1) the bacteria of fermentation, such, for example, as the lactic acid bacteria; (2) the putrefactive bacteria, such as the anaërobic B. aërogenes capsulatus; (3) bacteria of the B. coli type, showing the character of both the fermentative and putrefactive organisms but tending in general to antagonize the putrefactive anaërobes.”[57]

Fermentation in the Stomach.—In the stomach, fermentation of the carbohydrates with the production of organic acids, and at times alcohol, occurs. The types of fermentation taking place in the stomach are alcoholic, lactic, butyric, acetic, formic, oxalic, and cellulose. The bacteria inhabiting the gastric organs are dependent upon air for existence, while those in the intestines are not.

Factors Influencing Excessive Fermentation.—The factors influencing excessive fermentation in the stomach are lack of “tone” and motility in the organ, insufficient amount or absence of free hydrochloric acid in the gastric secretion, dilatation of the stomach, and an excess of carbohydrate foods in the diet. Of the latter, sucrose and glucose are especially susceptible to the action of fermentative bacteria. Under normal conditions, that is, in health, the conditions prevailing in the stomach are very unfavorable to the development of bacteria of the putrefactive type, the gastric juice exhibiting decided germicidal properties. Then, too, the presence of air acts against their development. Much of the so-called gastric fermentation does not occur in the stomach but rather in the duodenum.

Bacterial Action in the Intestines.—In the lower part of the small and in the large intestines, the bacteria of the anaërobic type increase, conditions more favorable to their development existing there than farther up in the intestinal tract. However, there are a great many bacteria in the whole of the small intestine. Those producing decomposition of the unabsorbed proteins are especially prominent in the colon.

Herter[58] states that “the presence in the colon of immense numbers of obligate micro-organisms of the B. coli type may be an important defense of the organism in the sense that they hinder the development of that putrefactive decomposition which, if prolonged, is so injurious to the organism as a whole. We have in this adaptation the most rational explanation of the meaning of the myriads of colon bacilli that inhabit the large intestine. This view is not inconsistent with the conception that under some conditions the colon bacilli multiply to such an extent as to prove harmful through the part they take in promoting fermentation and putrefaction.”

Effect of Bacterial Activity in the Body.—In summarizing the effects of bacterial action in the body it is found that with the exception of oxalic acid, which is exceedingly injurious, and which, according to Herter, results from the eating of large quantities of meat and sugar, the products of fermentation are simply irritating in character, while those resulting from putrefaction are distinctly toxic. Among the substances deserving mention under this head we have indol, skatol, cresol, and phenol. These substances are very soluble and upon absorption combine with the sulphuric acid formed in the body and are excreted by way of the kidneys where they appear in the urine as “conjugated sulphates,” the chief of which is indican. The amount of indican in the urine is taken as a measure of the intensity of the putrefaction taking place in the body.

Metabolism.—Under the term metabolism we understand the series of processes through the foodstuffs and carried (a) in the conservation of the tissues of the body and (b) in the maintenance of body temperature and physical work (Taylor). The processes concerned in metabolism are chiefly those of building up, “anabolism,” and breaking down, “catabolism.” In the processes of anabolism the products absorbed are built into the tissues and cells of the body. In catabolism, the worn particles from the cells, and the dead cells no longer useful are broken up and thrown out of the body. According to Taylor, “side by side with these processes are the reactions of combustion, whereby the temperature necessary for the life of the cells is maintained, and the energy needed for external work furnished.”

Behavior of Carbohydrates in Metabolism.—As Sherman[59] has said: “At least two kinds of enzymes are believed to be involved in the combustion of glucose in the tissue cells, (1) cleavage enzymes, which split the molecule into fragments more easily oxidized, and (2) oxidizing enzymes or oxidases which stimulate the oxidation of the cleavage products. Both kinds of enzymes are widely distributed through the body and are believed to be normal constituents of all active cells.”

Production of Energy.—It has been proved that the energy for external and internal work is produced largely from the glucose brought by the blood and oxidized in the muscles.

When a surplus amount of carbohydrate food is eaten, over and above the immediate needs of the body for fuel, it is stored in the liver and muscles as glycogen, which can be readily reconverted into glucose. When the supply of carbohydrate food is greatly in excess of the body’s needs, that is when the liver and muscles cease to store glycogen, it is built up into adipose tissue and furnishes a readily available source of emergency fuel.