YEAST
From time to time yeast has attained a transitory popularity as a therapeutic agent. Its use in this way in practical medicine has been based essentially on empiric considerations. Yeast is rich in nucleic acid, but this has not found any special applications. The fatlike substances obtainable from yeast have been recommended in certain alimentary conditions, without finding any widespread acceptance.
More recently yeast has acquired interest from somewhat different angles. In these days of food shortage and enforced conservation, it has come to be realized that the minute yeast cells are endowed with a remarkable capacity of synthesizing one of the most valued nutrients, namely, protein. This substance can be built up out of the simplest forms of nitrogenous compounds by yeasts, in contrast with the incapacity of the higher organisms to construct protein out of anything less complex than the ready made aminoacids. It is reported that in Europe yeast has actually been grown on a large scale in solutions of sugar, salt and simple nitrogenous compounds for the sake of securing the much desired proteins. The utilization of yeast protein for cattle feeding is a current practice abroad; and the satisfactory digestibility and availability of the same product by the human organism has repeatedly been announced since the beginning of the war. In this country the yeast which is produced as a by-product of the brewing industry is for the most part discarded as waste; in the distilleries it becomes a part of the distillers’ grains that are extensively employed as feeds in the dairy industry.
Still newer is the indication that yeast is comparatively rich in at least one of the as yet unidentified accessory factors in nutrition now popularly spoken of as vitamins. Hopkins of the University of Cambridge, England, first directed attention to this unique property of yeast. It has been verified by Funk and Macallum, and recently Osborne and Mendel have given substantial evidence of the potency of yeast to render a diet not otherwise capable of inducing maintenance effective in nutrition.
Yeast has been used, like extracts of rice polishings, to cure the experimental polyneuritis induced in birds by a diet of polished rice. From the experiments of Osborne and Mendel it appears that less than 2 per cent. of dried brewers’ yeast suffices to induce small experimental animals to grow on artificial food mixtures on which alone they fail to thrive. How the use of yeast as an adjuvant to otherwise inadequate food mixtures exerts its beneficial effect is not yet made clear. Satisfactory growth in these cases is promoted by liberal eating. Anything which renders food more palatable may stimulate one to eat more liberally of it. This can scarcely be the explanation of the potency of the yeast as it is effective even when fed apart from the rest of the food. It may have a favorable effect on the metabolism and thus improve the general condition so that more food is consumed. Small quantities of milk and extracts of many of the common plant foods, such as the cereal grains, have been found to act in the same way. There seems to be little doubt, therefore, that yeast also contains something comparable with the so-called water-soluble vitamins of the diet. A specific need for yeast can scarcely be predicated on this fact, however; for any well selected human dietary containing the usual variety of animal and vegetable foods is not likely to be devoid of the widely distributed water-soluble type of vitamin. We mention this to check premature enthusiasm for a new vitamin.—(Editorial from The Journal A. M. A., Sept. 8, 1917.)
Yeast and Its Uses
To the Editor:—Is there available information concerning the medicinal use of yeast? How is it taken? I should like to know whether the use of it would cause any digestive disturbance, and whether the flesh gained is normal and permanent.
S. E. L., Bridgeport, Conn.
Answer.—Yeast is one of those remedies that have undergone alternating cycles of use and of disuse; just at present it appears again to be in its ascendency. No doubt, the reason for these cycles has been excessive praise and uncritical use, followed by disappointment and consequent discard.
Hawk and his associates (Hawk, P. B.; Knowles, F. C.; Rehfuss, M. E., and Clarke, J. A.: The Use of Bakers’ Yeast in Diseases of the Skin and of the Gastro-Intestinal Tract, The Journal, Oct. 13, 1917, p. 1243) have recently called renewed attention to its laxative qualities. When from one-half to one cake of yeast was given three times daily before meals, it produced regular bowel movements in a number of patients suffering from constipation. That this result is not due to any vital processes in the yeast is shown by the fact that yeast killed by boiling water was employed with success. It is suggested that such yeast might be preferred for patients troubled with flatulence. Aside from the tendency of living yeast to produce diarrhea, and the possibility that it may aggravate flatulence, no digestive disturbance has been charged against it. Aaron, in his “Diseases of the Digestive Organs,” speaks favorably of its use in atonic constipation.
The much debated question whether yeast may serve as a food can be answered in the affirmative in view of such work as that of the Germans on “Nährhefe”—yeast food (Schottelius, Deutsch. med. Wchnschr., July 8, 1915, p. 817) and Boruttau (ibid., July 29, 1915, p. 924) and of Hawk and his associates. There is no reason to assume that weight gained under its use would be more readily lost than weight gained from any other food. However, in view of its laxative action, the average individual can ingest only from 1 to 2 gm. of nitrogen a day in this form. This obviously greatly limits its value as a food. Owing to its high nuclein content, it is contraindicated in gout.
As a source of water soluble growth promoting as well as antineuritic vitamin, yeast has become thoroughly established as the result of the recent works of numerous investigators. However, as such common foods as milk, rice, wheat, oats and beans also contain such vitamin, there is little likelihood of its proving of therapeutic value on that account. In other words, yeast and other vitamin containing foods have specific growth promoting qualities only when the stunting is due to lack of vitamin. A minute amount of this substance suffices to produce maximal results. More is of no use. Hess (Proc. Soc. Exper. Biol. & Med. 13:145, 1916) found yeast of no value in infantile scurvy.
The most important question in connection with yeast therapy is to what extent it is endowed with “antibiotic” power, that is, to what degree it is capable of inhibiting the growth of other organisms. That this frequently occurs in cultures in vitro is shown by the fact that yeast contamination may practically eradicate the growth of certain other organisms. That, on the other hand, this is not true for all forms of bacterial life is shown by the fact that there is definite symbiosis between yeast and lactic acid bacilli (Northrup: Soc. Tech. Bull. 15, Mich. Agr. Expa. Sta., 1912).
That its “antiseptic power is, on the whole insignificant” has been shown by Palier (Diet. & Hyg. Gaz., March, 1906), who found commercial yeasts commonly contaminated with numerous bacteria, the most frequent being Bacillus coli-communis or one of its congeners. An antagonistic action by yeast is claimed against Staphylococcus pyogenes, and on the strength of this, Buchholtz (Ueber Acne und eine neue erfolgreiche Behandlung derselben, Berl. klin. Wchnschr., Feb. 2, 1914, p. 215) employed it locally in the treatment of acne and obtained a positive but temporary effect. He believes that the effect is improved by the combination of yeast with an equal quantity of boric acid. He employed this as a dusting powder applied freely to the skin once daily, after the application of a thin layer of a boric acid salve (boric acid powder from 40 to 50, glycerin and water, of each 100) to make it stick better. In cases in which the nose was markedly involved, he also used this as a snuff. Yeast poultices have been employed with asserted great benefit in the treatment of wound infection of all kinds (Kempf, E. J.: Ind. M. J., September, 1904, p. 97).
The use in leukorrhea was recommended by Hippocrates Abraham (Mon. Geb. Sym., 1910) and many others report favorable results from yeast in the treatment of gonorrheal vaginitis. In various gastro-intestinal infections, yeast has been lauded by many, among others, Thiercelin and Chevrey. It has been given by mouth, but most especially in high rectal enemas.
Still more from a theoretical standpoint is the reassertion of the curative value of the oral administration of yeast in various cutaneous disorders. Thus Hawk and his collaborators report cure or improvement in all of seventeen cases of acne vulgaris and eight cases of acne rosacea. They also report seventeen cases of furunculosis, in all but one of which there was cure or improvement from yeast treatment. They are unable to decide whether the result is due to the laxative action, the production of leukocytosis, or to other influences.
Yeast is probably best taken incorporated in food. Hawk and his associates found that yeast may well be incorporated in wheat biscuits, and that in this way a yeast-wheat combination of most agreeable flavor was produced: that, in fact, the biscuits with the yeast tasted better than those without it. They found by tests that in bread making as much as 20 per cent. of the flour might be replaced by dry yeast, and that thereby a loaf would be produced that was excellent in every way and possessed of an attractive flavor. The dry yeast was prepared by desiccating compressed yeast at 105 C. in a current of air, and then milling it to produce a flour of the approximate fineness of ordinary wheat flour. They also found that yeast may be added to meat preparations, such as Hamburger steak, to the extent of 2.5 per cent., yielding a preparation of very satisfactory taste.—(Query in The Journal A. M. A., Aug. 23, 1919.)