DIETICAL PROPERTIES.
That the universal employment of tea has displaced many other kinds of food is certain, and regarding its dietical properties much has been written for and against. While some physicians have praised its value as an article of food, on account of the large proportion of nitrogen which it contains, others have as strenuously maintained that it is non-nutritious, and does not serve as a substitute for food, and that the only beneficial properties it contains are due to the milk and sugar added in its use. So that in considering the nourishing effects of tea, the nutriment contained in the milk and sugar certainly must not be overlooked, neither must the powerful influence of the heat of the steaming draught be forgotten. According to the chemical classification of food, the “flesh formers” contained in tea of average quality is about 18, and the “heat givers” 72 per cent., water and “mineral matter” being divided between the residue, the several constituents as they are found in one pound of good tea being as follows:—
The use of theine as an article of diet has not so far been satisfactorily determined; but that it is a question of no mean interest is obvious when we consider that it is found to exist in so many plants, differing widely in their botanical origin and yet all instinctively used for the same purpose, by remotely situated nations, for the production of useful, agreeable and refreshing beverages.
By taking the normal temperature of the human body at 98°, it follows that where food is taken into the stomach of a lower temperature than that of the body it must necessarily abstract heat from the stomach and surrounding tissues, so that where the practice of taking cold food becomes habitual depression occurs and the stomach is consequently disordered, and the system must make good this heat lost in raising the temperature of cold food or else suffer. The body demanding food when in an exhausted state, cold food or drink makes an immediate drain upon the system for heat before it can supply material for producing combustion, and the body is thereby taxed to supply heat at a time when it is least fitted for it. It is natural, therefore, that there should be a craving for warm food, and as liquid food is deficient in heat-giving matter, the use of cold drink is more injurious than that of cold food. From other experiments it appears that the introduction into the stomach of three or four grains of theine, which is the quantity contained in the third of an ounce of good tea, has the remarkable effect of diminishing the daily waste or disintegration of the bodily tissues which may be measured by the quantity of solid constituents contained in the many secretions, and if such waste be lessened the necessity for food to repair that waste will obviously be decreased in corresponding proportions. In other words, says Professor Johnstone, “by the consumption of a certain quantity of tea daily the health and strength of the body will be maintained to an equal degree upon a smaller supply of ordinary food.” Tea, therefore, saves food; stands to a certain extent in place of food, while at the same time it soothes the body and enlivens the mind. While tea, according to Dr. Sigmond, “has in most instances been substituted for spirituous liquors, and the consequence has been a general improvement in the health and morals of the people, the time, strength, and vigor of the human body being increased by its use. It imparts greater capability of enduring fatigue, and renders the mind more susceptible of the innocent and intellectual pleasures of life, as well as of acquiring useful knowledge more readily, being not only a stimulant to the mental faculties but also the most beneficial drink to those engaged in any laborious or fatiguing work.” Dr. Jackson testifying “that a breakfast of tea and bread alone is much more strengthening than one of beefsteak and porter.”
In his admirable work on hygiene Dr. Parker remarks that “tea possesses a decidedly stimulating and restorative action on the human system, no depression whatever following its use, the pulse being a little quickened, and the amount of pulmonary carbonic acid accordingly increased.” From this experiment he regards “tea as a most useful article of diet for soldiers, the hot infusion being potent against heat and cold, and more useful still in great fatigue in tropical countries by its great purifying effect on brackish and stagnant water.” Adding that “tea is so light, easily carried and so readily prepared, that it should form the drink, par excellence, of the soldier in service or on the march, above all its power of lessening the susceptibility to malarial and other influences.” And Admiral Inglefield is quoted as strongly recommending the use of tea to Arctic travelers and explorers, as seamen who surveyed with him in the polar regions after an experience of one day’s rum drinking came to the conclusion that tea was more beneficial to them while undergoing the severe work and intense cold. Under the infirmities of advancing age, especially when the digestive powers become enfeebled and the size and weight of the body begin perceptibly to diminish, the value of tea in checking the rapid waste of tissue is particularly observable, and persons, when very much fatigued, will be sooner refreshed by drinking a cup of moderately strong, good tea, than by drinking wine or spirits of any kind. In allaying or satisfying severe thirst, no beverage will be found as efficacious as a draught of cold tea.
Lettson furnishes a calculation, partly his own and partly from other sources, in which he endeavors to prove how much is, in his view, unnecessarily expended by the poor for tea. But the observations of Liebig, if correct, and in all probability they are, offer a satisfactory explanation of the cause of the partiality of the poorer classes, not alone for tea, but for tea of an expensive and therefore superior quality. “We shall never certainly,” he says, “be able to discover how people were led to the use of hot infusions of the leaves of a certain shrub (tea) or a decoction of certain roasted seeds (coffee); some cause there must be which would explain how the practice has become a necessary of life to whole nations.” But it is still more remarkable that the beneficial effects of both plants on the health must be ascribed to one and the same substance, the presence of which in two vegetables belonging to natural families, the product of different quarters of the globe, could hardly have presented itself to the boldest imagination, recent research having shown in such a manner as to exclude all doubt that the caffeine of coffee and the theine of tea are in all respects identical. And without entering into the medical action of this principle, it will surely appear a most startling fact, even if we deny its influence on the process of secretion, that this substance, with the addition of oxygen and the elements of water, can yield taurine, the nitrogenous compound peculiar to bile. So that if an infusion of tea contain no more than 1-10 of a grain of theine, and contributes, as has been shown, to the formation of bile, the action, even of a such a small quantity, cannot be looked upon as a nullity. Neither can it be deemed that in the case of non-atomized food or a deficiency of the exercise required to cause a change of matter in the tissues, and thus to yield the nitrogenized product which enters into the composition of bile, the health may be benefited by the use of compounds essential to the production of this important element of respiration. In a chemical sense, and it is this sense alone that theine is in virtue of its composition better adapted to this purpose than all other nitrogenized vegetable principles yet discovered. To better prove how the action of tea may be explained, we must call to mind that the chief constituents of the bile contain only 3.8 per cent. of nitrogen, of which only one-half belongs to the taurine. Bile contains in its natural state water and solid matter in the proportion of 90 parts of the former to 10 parts of the latter, and if, we suppose, these 10 parts of solid matter to be cholenic acid with 5.87 per cent. of nitrogen, then 100 parts of bile must contain 0.171 of nitrogen in the form of taurine, which quantity is contained in .06 parts of theine, or, in other words, 272 grains of theine can give to an ounce of bile the quantity of nitrogen it contains in the form of taurine. The action of the compound in ordinary circumstances is not obvious, but that it unquestionably exists and exerts itself in both tea and coffee is proven by the fact that both were originally met with among nations whose diet was chiefly vegetable. These facts clearly show in what manner tea proves to the poor a substitute for animal food, and why it is that females, literary persons and others of sedentary habits or occupation, who take but little exercise, manifest such a partiality for tea, and also explain why the numerous attempts made to substitute other articles in its place have so signally failed.