The Chemistry of Food and Nutrition - A. W. Duncan (latest books to read .TXT) 📗

is alkaline and assists the pancreatic juice in neutralising the acid mixture that leaves the stomach; it also assists the absorption of fats. The digestion of proteids is not completed in the stomach. There are some who look upon the stomach as chiefly of use as a receptacle for the large mass of food, which is too quickly eaten to be passed at once into the intestines; the food being gradually expelled from the stomach, in such quantities as the duodenal digestion can adequately treat. A frequently used table, showing the time required for the digestion of various foods in the stomach, is of little practical value. There is ample provision for the digestion of food, there is a duplication of ferments for the proteids and starch. In health, the ferments are not only very active, but are secreted in ample quantities. The digestive or unorganised ferments must not be confused with the organised ferments such as yeast. The latter are living vegetable cells, capable of indefinite multiplication. The former are soluble bodies, and though capable of transforming or digesting some thousands of times their mass of food, their power in this direction is restricted within definite limits. Another and preferable name for them is enzymes.

The action of saliva on starch is powerfully retarded by tea, this is due to the tannin. Coffee and cocoa are without effect. Tea infused for two minutes only, was not found to have sensibly less restraining effect than when infused for thirty minutes. On peptic digestion both tea and coffee had a powerful retarding effect. When of equal strength cocoa was nearly as bad, but as it is usually taken much weaker, its inhibitory effect is of little consequence.

Bacteria are minute vegetable organisms, which exist in the dust of the air, in water and almost everywhere on or near the surface of the earth. They are consequently taken in with our food. They exist in the mouth; those in carious teeth are often sufficient to injuriously affect digestion and health. The healthy gastric juice is to a great degree antiseptic, but few bacteria being able to endure its acidity. When the residue of the food reaches the large intestine, bacteria are found in very great numbers. The warmth of the body is highly favourable to their growth. They cause the food and intestinal debris to assume its fæcal character. Should the mass be retained, the bacterial poisons accumutate and being absorbed into the body produce headaches, exhaustion, neurasthenia and other complaints. Proteid matter, the products of its decomposition and nitrogenous matter generally, are especially the food of bacteria; this is shown in the offensiveness of the fæces of the carnivora, notwithstanding their short intestines, compared with that of the herbivora. Also in the difference of the fæces of the dog when fed on flesh and on a nearly vegetable diet. On a rich proteid diet, especially if it consists largely of flesh, the bacterial products in the intestines are greater than on a vegetable diet. On the latter such a disease as appendicitis is rare. Professor Elie Metchnikoff, of the Pasteur Institute, thinks that man's voluminous and highly developed large intestine fulfils no useful purpose, and on account of its breeding a very copious and varied bacterial flora, could with advantage be dispensed with. He also has said that man, who could support himself on food easily digestible, has a small intestine which is disproportionately fully developed. Instead of having between 18 and 21 feet of small intestine, man might do with one-third of that length. According to him, there is a disharmony of our food and our digestive system. Referring to such views, and the desire of some surgeons to remove the vermiform appendix and portions of the intestines upon too little provocation, Sir W. Macewin, M.D., F.R.S. (B. Medical Jrn., 1904, 2 p. 874) says:—"Is this human body of ours so badly constructed that it contains so many useless parts and requires so much tinkering? Possibly I may be out of fashion with the times, as I cannot find such imperfections in the normal human body as are alleged. On the contrary, the more one looks into the human body and sees it work, the better one understands it and the more one is struck with the wondrous utility, beauty, and harmony of all its parts." Our food we can change, but not our organs-except by a dangerous surgical operations. Our teeth with our complex and very long intestines are adapted for fibrous, bulky and solid food. On such food mankind has lived for an immense period of time. It is true that there are several theoretical advantages in cooked vegetable foods; but unfortunately there is a want of conformity with our digestive organs. If a flesh diet is taken, the incongruity is greater. Concentrated food causes constipation. An active man, leading an out-of-door life, can take unsuitable food with little or no apparent inconvenience, the movements of his body favouring intestinal action; whilst the same food to a sedentary person will prove distinctly injurious.

Some persons have such a vigorous digestion that they can consume almost any food, even that which is obviously unsuitable; not only bad in kind but excessive in quantity. Other persons have to be very careful. Many have boasted that they can take of what they call the good things of life to their full, without bad effect. We know of such men who have been much esteemed for their joviality and good nature, but who have broken down in what should have been a hearty and useful middle life. There are others who were poorly equipped for the battle of life, with indifferent constitutions, never having had the buoyancy and overflowing of animal spirits; but who, by conserving such strength as they had, have outlived all their more healthy but less careful comrades. The errors of the parents are often most evident in the children or grandchildren. There are many persons who cannot eat of some particular food, although it may be quite wholesome to others. Sometimes it is a psychological rather than a physiological disability, which may he overcome by an effort of the will. At other times it seems to have no connection with the imagination, although it is not always possible to give a sound reason for it. In the main, of course, there are principles of dietetics applicable to all alike, but in regard to details, everyone should make rules for himself, according to his experience. When there appears no real reason for an idiosyncrasy, a little humouring of our taste and digestion will often overcome it, to our advantage. It is generally those of delicate constitution who are most sensitive. Some cannot eat oatmeal except in small quantity. Olive and other vegetable oils, even when of good quality cannot be taken by many people, whilst others find them quite as wholesome, or even better than butter. Vegetarians can generally detect lard in pastry both by its taste and its after effects, although those accustomed to this fat do not object to it. It is also surprising how some individual's tastes and habits will vary at different periods of their lives.

One form of dyspepsia is due to undigested starch remaining in the stomach and causing an excessive secretion of hydrochloric acid. As long as proteid food is present, the pepsin and acid expend themselves on it, and are removed together. The undigested starch continues to stimulate gastric secretion, and the acid residuum causes pain, heartburn and flatulence. If there be also any butyric acid, or some other fatty acid, derived from milk, butter, cheese, &c., there will be acid eructations. For this form of indigestion there are several methods of treatment. First; the very thorough cooking of all starchy food, and it is an advantage to take a little good extract of malt, either at the time of eating or directly afterwards. The diastase of the malt has the same action on starch as the ptyalin in the saliva. It is better, scientifically, to have the farinaceous food at about 130° F. (as hot as the mouth can bear will do), and then to add malt extract. On keeping the mixture warm, from a few minutes to half an hour or more, the starch is digested and rendered soluble. Such food is not very pleasant to take. The food known as Grape Nuts has been treated in a similar manner. The use of malt extract, however, seems a clumsy substitute for salivary digestion. Second; the eating of starch in the form of hard and dry biscuits, crusts and other hard food, which demand thorough mastication and insalivation, and the keeping in the mouth for a long while, during which the saliva has time to act. This is the best plan. Third; the taking of sodium bicarbonate towards the end of the period of digestion, in order to neutralise the acid in the stomach. This gives relief, but does not cure, as the dose has to be repeated after each meal; in course of time the quantity of soda has sometimes to be increased to an alarming extent. Fourth; the abstention from starchy foods and the substitution of an exclusive flesh dietary. In the "Salisbury" treatment, raw minced beef is given. This method often gives immediate relief, but its ultimate effect on the kidneys and other organs is very bad.

No hard and fast rule can be laid down as to the number of meals into which the daily amount of food required should be divided. The stomach appears to work to the best advantage when it is full, or nearly so, and the appetite is appeased. Three approximately equal meals seems to be a convenient division. Dr. Dewey and his followers advise only two meals a day, and it seems incontestable that many persons find the plan advantageous. These are generally adults with weak digestions, or elderly persons who, on account of their age and the sluggish action of their assimilative functions, require comparatively little food. Children, on account of their vigorous vitality, rapid growth and hearty appetites, ought not to be restricted to this number. Persons who have got into the pernicious habit of greatly over-eating, and whose stomachs have become distended and unusually large, sometimes find it easier to restrict their daily food to a healthy quantity by taking only two meals. The general objections against two meals are that either two little food is taken, or the ingestion of such a large quantity is bad for the stomach and causes it to press on the adjacent viscera. The large quantity of blood and nerve force drawn to the over-distended stomach, depletes the brain and nervous system, causing drowsiness and incapacity for mental and physical work. The carnivora, whose opportunity for obtaining food—unlike the herbivora—is irregular and often at long intervals, gorge themselves upon opportunity and are in the habit of sleeping after a meal. The frugivora and herbivora, however, are alert and ready to fly from their enemies should such appear. The conveying of so much nourishment to the liver and blood stream at one time, is probably a greater tax on them. A light lunch between the usual full meals has nothing to recommend it. The stomach is burdened to little purpose, often before it has finished with one meal another is imposed upon it, no time being left for recuperation.

Dietaries.—The best proportions of proteids, carbo-hydrates and fats required for the nourishment of the body has not yet been conclusively decided. The common plan is to average the dietary of large bodies of persons, particualrly of soldiers and prisoners. These dietaries have been adjusted empirically (the earlier ones at least), and are generally considered as satisfactory. They are chiefly of English and German origin. Another method is to laboriously analyse the injesta or food consumed and compare it with the dejecta or excretions, until a quantity and kind of food is found which is just sufficient to keep the body