Physiological economy in nutrition, with special reference to the minimal proteid requirement of the healthy man an experimental study

Part 55

Chapter 553,858 wordsPublic domain

Obviously, a lowered proteid intake means, in some measure at least, a decreased consumption of meat and similar products more or less rich in free and combined purin bases. This quite plainly must result in a diminished production of uric acid, but the writer is strongly of the opinion that we do not as yet possess sufficiently full knowledge regarding all the ways in which uric acid results in the body. It is true, we differentiate between endogenous and exogenous uric acid, and further, we understand quite clearly that variations in the intake of free and combined purin bases exercise a potent influence upon the output of uric acid through the urine. We still lack, however, concise information as to the various ways in which uric acid may be produced, and its ultimate fate in the body. This is well illustrated by a recent paper from the Marburg laboratory, in which Kutscher and Seemann[52] point out the possibility of a production of uric acid in the animal body synthetically, and likewise suggest that uric acid may be utilized for the formation of nuclein bases, _i. e_., a reversal of the oxidative process by which uric acid results from the ingestion of free or combined nuclein bases, suggesting indeed the possibility of uric acid and the nuclein bases being produced from each other, according to the circumstances. Thus, when nucleins or free purin bases are taken with the food, the organism may utilize this material at once in the synthesis of nucleins for the use of the body cells. There is no need of a reduction of the formed uric acid to nuclein bases, and consequently there is an increased excretion of uric acid through the urine, but this does not result from a direct transformation of the ingested purin material into uric acid, but is the result of a sparing of the already formed uric acid. The nuclein bases thus act as sparers of uric acid. This view explains, according to Kutscher and Seemann, why feeding with nuclein bases increases the output of uric acid, and feeding with uric acid—a sudden overflow of uric acid into the circulation—is followed, as a rule, by an increased elimination of urea, the uric acid being thus transformed by energetic oxidation. This hypothesis is brought forward not merely because it is an interesting suggestion, but mainly because it illustrates that we do not as yet know fully all the steps in the production of uric acid, nor do we know how far the uric acid we find and determine in the urine is a measure of the formation of uric acid in the body.

Taking our knowledge on these matters as it stands to-day, however, we find by experiment that lowering the intake of proteid food, with its consequent corresponding diminution in proteid katabolism, is followed at once by a marked decrease in the output of uric acid. Let us consider a few of the data obtained in our experiments. The first case I will refer to is that of a college athlete (Callahan). For a period of ten days on his ordinary diet, the average amount of nitrogen in the urine per day was 22.8 grams, equal to the metabolism of 142.5 grams of proteid food. During this same period the average daily output of uric acid was 1.103 grams. For the following four months and a half, on a more restricted diet, with a marked cutting down of the proteid food, but with no exclusion of meat, the average daily output of nitrogen through the urine was 9.04 grams. In other words, for this period of over four months the extent of proteid katabolism was reduced considerably more than 50 per cent. The average daily output of uric acid for this same period was 0.624 gram, equal to a reduction of about 40 per cent from his normal excretion.

Another college athlete (Stapleton), on his normal diet, showed an average excretion of nitrogen through the urine per day, for ten days, of 19.70 grams, while the daily average excretion of uric acid for the same period was 0.893 gram. On a more restricted diet, with diminished proteid katabolism, the daily average excretion of nitrogen through the urine for a period of over four months was 11.06 grams, while the daily average excretion of uric acid for the same period fell to 0.699 gram. In the first of these two cases the average daily ratio of uric acid to total nitrogen during the period of lowered proteid metabolism was 1:14. In the second case the ratio was 1:16.

A third college student (G. W. Anderson), on his ordinary diet, excreted through the urine for a period of nine days 17.17 grams of nitrogen as the daily average, while the average daily output of uric acid for the same period was 0.956 gram. On the more restricted diet of the next four or five months his average daily excretion of nitrogen fell to 9.37 grams per day, while the average daily excretion of uric acid was reduced to 0.632 gram. On his ordinary diet, the ratio of uric acid to nitrogen was 1:18, while later with the diminished proteid metabolism the ratio was 1:14.

Turning to another class, viz., professional men, reference may be made to the writer, whose average daily nitrogen excretion through the urine for a period of nearly nine months was 5.699 grams, corresponding to the metabolism of 35.6 grams of proteid per day. During this same period of nearly nine months the average daily excretion of uric acid amounted to 0.392 gram, the ratio of uric acid to total nitrogen being 1:14. In passing, it may be repeated that the subject of this experiment succeeded in maintaining a constant body-weight, and he further avers that in physical and mental vigor he can find no evidence of deterioration, although the amount of proteid food consumed daily during this long period was less than 40 grams per day. Further, he was in nitrogenous equilibrium during this period, although the nitrogen metabolized daily amounted to only 99 milligrams per kilo of body-weight. Another case in this same group may be mentioned, principally because the subject for over a year became a vegetarian, abstaining from all meat. During the last nine months, this man (Beers) eliminated 8.28 grams of nitrogen through the urine as the daily average, indicating a metabolism of 51 grams of proteid material per day. During this same period, the average daily excretion of uric acid was 0.349 gram, the ratio of uric acid to total nitrogen being 1:23.

The main point to be emphasized in these results is that they show quite conclusively how greatly the daily output of uric acid may be reduced by diminishing the intake of proteid food, and thereby restricting the extent of the proteid metabolism. The ratio of uric acid to the total nitrogen excreted may or may not be altered; this will depend in large measure upon the character of the diet, the relative proportion of free and combined purin bases introduced with the food, etc. As already stated, we do not know with certainty how far the excreted uric acid represents the formation of uric acid in the body, but presumably there is a more or less close relationship, and hence we are doubtless warranted in saying that the formation of uric acid is diminished, in essentially the same proportion as its excretion is reduced, with a lowered proteid intake. Certain it is that several of the persons under observation, who had troubles of a gouty and rheumatic nature in the past, have during the course of the experiment experienced relief, with complete and permanent abeyance of all symptoms. The writer is firmly of the opinion that ordinary gout and rheumatism are entirely preventable by reasonable care and judgment in the matter of diet. Whether, when once firmly established, in aggravated form, they will prove amenable to dietetic treatment is not so certain, but undoubtedly mild cases will respond to the beneficial influences of a rational diet, reinforced by treatment adapted to the removal of urates already deposited. In any event, due regard for the well known deleterious effects of purin-containing foods as a source of exogenous uric acid, and with restriction of proteid metabolism to the true necessities of the body, should serve as an effective means of preventing all those troubles for which uric acid is generally held responsible.

The two following tables give a summary of results bearing upon the excretion of uric acid and its relation to nitrogen and body-weight, for all the subjects belonging to the “professional group” and the “student group.” Emphasis should be laid upon the fact that these figures represent the average daily excretion for the different individuals through the entire period of the experiment.

AVERAGE DAILY EXCRETION THROUGH THE URINE FOR SEVEN-NINE MONTHS.—PROFESSIONAL GROUP.

AVERAGE DAILY EXCRETION THROUGH THE URINE FOR FOUR-FIVE MONTHS.—STUDENT GROUP.

+---------------+-------+---------+------+---------+---------+----------+ | | | | |Ratio of |Uric Acid| | | Name. |Body- |Total | Uric |Uric Acid| per kilo|Phosphoric| | |weight.|Nitrogen.| Acid.| to |of Body- |Acid | | | | | |Nitrogen.| weight. |P₂O₅. | +---------------+-------+---------+------+---------+---------+----------+ | | kilos | grams | gram | | grams | grams | |Anderson, G. W.| 71.0 | 9.37 | 0.632| 1:14 | 0.0089 | 1.75 | |Anderson, W. L.| 61.0 | 10.41 | 0.516| 1:20 | 0.0084 | 2.14 | |Bellis | 78.0 | 8.88 | 0.531| 1:16 | 0.0068 | 1.98 | |Callahan | 83.0 | 9.04 | 0.624| 1:14 | 0.0075 | 1.74 | |Donahue | 62.0 | 7.47 | 0.395| 1:19 | 0.0063 | 1.79 | |Jacobus | 56.0 | 7.58 | 0.423| 1:17 | 0.0075 | 1.67 | |Schenker | 73.0 | 10.09 | 0.624| 1:16 | 0.0085 | 2.20 | |Stapleton | 75.0 | 11.06 | 0.609| 1:16 | 0.0093 | 2.64 | +---------------+-------+---------+------+---------+---------+----------+

Turning now to the third group of men, _i. e._, the soldier detail, under observation for a period of six months, during five months of which time they lived on a prescribed diet with diminished content of proteid food, but with no exclusion of animal food, the following average results are to be noted:

AVERAGE DAILY EXCRETION THROUGH THE URINE FOR FIVE MONTHS—SOLDIER DETAIL.

+---------------+-------+---------+------+---------+---------+----------+ | | | | |Ratio of |Uric Acid| | | Name. |Body- |Total | Uric |Uric Acid| per kilo|Phosphoric| | |weight.|Nitrogen.| Acid.| to |of Body- |Acid | | | | | |Nitrogen.| weight. |P₂O₅. | +---------------+-------+---------+------+---------+---------+----------+ | | kilos | grams | gram | | grams | grams | |Oakman | 62 | 7.42 | 0.405| 1:18 | 0.0065 | 1.39 | |Morris | 59 | 7.03 | 0.450| 1:15 | 0.0076 | 1.25 | |Broyles | 60 | 7.26 | 0.398| 1:18 | 0.0066 | 1.41 | |Coffman | 58 | 8.17 | 0.379| 1:21 | 0.0065 | 1.23 | |Sliney | 60 | 8.39 | 0.647| 1:13 | 0.0107 | 1.32 | |Steltz | 53 | 7.13 | 0.416| 1:17 | 0.0078 | 1.24 | |Henderson | 71 | 8.91 | 0.488| 1:18 | 0.0068 | 1.42 | |Fritz | 72 | 7.84 | 0.642| 1:12 | 0.0089 | 1.58 | |Cohn | 62 | 8.05 | 0.512| 1:15 | 0.0082 | 1.28 | |Loewenthal | 59 | 7.38 | 0.372| 1:19 | 0.0063 | 1.28 | |Zooman | 55 | 8.25 | 0.457| 1:18 | 0.0083 | 1.19 | |Bates | 65 | 8.08 | 0.387| 1:20 | 0.0059 | 1.23 | |Davis | 57 | 8.61 | 0.414| 1:20 | 0.0072 | 1.42 | +---------------+-------+---------+------+---------+---------+----------+

These figures are interesting in many ways. First, they make clear that on the diet prescribed, these men were manufacturing or excreting about the same amount of uric acid per kilo of body-weight as the men of the two preceding groups, living more or less with free choice of food. In other words, all these men, with one and possibly two exceptions, were practically throwing out only uric acid of endogenous origin, _i. e._, that which came from the breaking down of the man’s own tissue cells. Second, it is to be noted that the ratio of uric acid to nitrogen in the men of this group varies only within narrow limits.

It is very evident from these figures, reinforced by those of the previous groups, that we can diminish greatly the output of uric acid by simply restricting the extent of proteid katabolism, through reduction in the amount of proteid food. Further, we now know that this general lowering of proteid metabolism can be accomplished not only without danger to the body, but with a distinct betterment of the physical condition.

Just here I should like to emphasize one point that appears to me of primary importance in any consideration of the influence of diet in gouty affections, and in so doing I merely echo a statement made by Sir Dyce Duckworth[53], viz., “that the subject of gout, either by inheritance or acquirement, is so far peculiar in his constitution that he reacts differently to various agencies, such as climate, food, etc., from persons not so disposed.” In this connection, let me refer again to the foregoing table of results obtained with the soldier detachment, remembering that these thirteen men were living under exactly the same conditions and consuming the same kind of food each day, and in essentially the same amounts. Yet notice the striking variation in the output of uric acid by one of these men (Sliney),—a variation which shows itself especially when the uric acid is calculated per kilo of body-weight. How can this variation be accounted for except on the assumption that there may be personal idiosyncrasies, personal coefficients of nutrition, natural or acquired, that modify to some extent the production of uric acid, the oxidation of uric acid, or the elimination of uric acid from the body?

Lastly, in advocating the possible systemic value of a lowered proteid metabolism as of value in the prevention of gout, and of other disorders which have their origin in perverted nutrition, I am inclined to emphasize the desirability of using common-sense in the application of dietetic rules, remembering that man is an omnivorous animal, and that Nature evidently never intended him to subsist solely on a “cereal diet,” or on any specific form of food to the exclusion of all others. On matters of diet every man should be a law unto himself, using judgment and knowledge to the best of his ability, reinforced by his own personal experiences. Vegetarianism may have its virtues, as too great indulgence in flesh foods may have its serious side, but there would seem to be no sound physiological reason for the complete exclusion of any one class of food stuffs, under ordinary conditions of life. Far more rational is temperance in place of prohibition, and I am inclined to emphasize the systemic value of a daily diet so reduced in quantity that the metabolic processes may be largely decreased, in closer harmony with true physiological needs, especially those which involve the breaking down of proteid matter; and in making this suggestion I can add the assurance, based upon these observations on many individuals, that there is not only perfect safety but gain to the body, in diminishing proteid metabolism to a level somewhere near the actual requirements of the individual.

V. ECONOMIC AND SOCIOLOGICAL IMPORTANCE OF THE RESULTS.

The importance of the foregoing results from an economic and sociological standpoint is perhaps worthy of a brief consideration. We have learned that a much smaller amount of albuminous or proteid food than is ordinarily consumed will suffice for the daily needs of the body. It remains to be seen whether this fact will gain the popular recognition it would seem to deserve. Ignoring for the time the matter of physiological economy and its possible bearing upon health and strength, it is a fair question to ask why should people indulge in such wasteful extravagance in the matter of diet when there is no real physiological need for it? Why not accustom the body to a smaller consumption of food, thereby saving for other purposes the expenditure which this excess of food involves?

The question of the daily diet is one of the most important for the family of small means, and there is no reason why the family treasury should be so heavily drained for this imaginary need. Simplicity of living might well be given more careful consideration, and now that we have convincing proof of much smaller dietetic requirements on the part of the body, it might be well to consider the practical application these results naturally suggest. It is obvious from our data, that it is quite safe to diminish by one-half the amount of albuminous or proteid food ordinarily consumed, and this without any apparent detriment to health, and with even gain to the economy. The ordinary forms of proteid food are, as a rule, the most costly of dietetic articles, and since this restriction of albuminous food calls for no great increase in the amount of non-nitrogenous food, it is quite apparent that a great saving in the daily expenditure can be accomplished.

Obviously, however, there must be a decided change in the attitude of the public on this question before any great improvement can be hoped for. Habit and sentiment play such a part in our lives that it is too much to expect any sudden change of custom. By a proper system of education commenced early in life it may, however, be possible to establish new standards, which in time may prevail and eventually lead to more enlightened methods of living, whereby there will be less drain upon the resources of the people. With habits firmly fixed and palates calling for new sensations, reinforced by the prevalent opinion that by hearty eating lies the road to health and strength, it is easy to foresee difficulty in the advance of new doctrines along the lines indicated. The pleasure of eating is not to be minimized. The palate serves as the gateway through which food passes, and its sensitiveness and power of appreciation are not to be despised.

Simplicity of diet, however, does not diminish but rather increases the pleasure of eating, especially when daily restriction in diet—indulged in until a new habit is formed—has created a greater keenness of appetite, since under such conditions the palate takes on a new sensitiveness, and manifests a fuller appreciation of the variations of even a simple dietary. There is therefore no hardship, nor curtailment of the pleasure of eating in the restriction of the diet to the real needs of the body. Neither is there implied any cessation of that kindly hospitality that delights in the ‘breaking of bread’ with one’s friends. With enlightened methods of living, on the other hand, will come a truer appreciation of the dignity of the body, and a lessened desire to manifest one’s feelings of hospitality by a lavish intemperance that is as unphysiological as it is wasteful.

For the rich, as well as for the poor, there is need for careful consideration of this question of intemperance in the daily dietary. Were this the proper place, it would be easy to adduce figures showing the great waste which the consumption of food beyond the physiological requirements of the body entails. It needs no great imagination to picture the enormous saving per capita, in dollars and cents, by a reduction of the daily food to a true physiological basis. The saving to the community, to the family, might well amount to enough to constitute the difference between pauperism and affluence. The resources of a community, as well as the resources of the family, are not to be lightly thrown away. We count the cost of this or that necessity, of this or that luxury, with careful consideration of the relative need and expense, but in the matter of living we pay little heed except it may be to exclude certain dietetic luxuries which seem beyond our purse. We are prone to fancy that health and strength are fostered by great liberality in the amount and variety of the daily food provided, and we are apt to express great concern if all the family and our guests do not avail themselves to the utmost of the foods so lavishly spread before them. The poorer man emulates his richer neighbors as soon as his circumstances will permit, and resources that could be much more advantageously expended for the good of the family and the home life are practically wasted—to say nothing of possible injury to health—under the mistaken idea that this more generous method of living is the surest road to health and strength.

Further, there is ground for thought in the possible economy of time which an improved condition of health would result in for the working members of the family. If greater economy in diet will diminish the number of sick days in the year, thereby increasing the working power of the wage earner, and if greater strength and efficiency can be acquired at the same time, the economic value of the proposition is at once apparent.

Finally, happiness and contentment, which usually appear in direct proportion to the health and prosperity of the individual, may be counted upon as becoming more conspicuous in the life of the community. So we see suggested various ways in which the application of the principles herein laid down, if consistently adopted and followed, may lead to a betterment of economic and sociological conditions. The writer, however, leaves to others, more familiar with sociological problems, the fuller development of this line of thought.

VI. GENERAL CONCLUSIONS.

When this investigation, the results of which have been detailed in the foregoing pages was first planned, it was intended to be simply a physiological study of the minimal proteid requirement of the healthy man, extended over sufficient time to render the results of scientific and practical value. There were no special theories involved, no special system of dietetics in view, but the object was simply to ascertain experimentally the minimum amount of proteid or albuminous food necessary for the maintenance of health and strength, under ordinary conditions of life. The impression in the mind of the writer was that there was no satisfactory scientific evidence to support the views held by most, if not all, physiologists regarding the needs of the body for food, especially nitrogenous or proteid food, and that the dietary standards universally adopted by scientific men were of very questionable accuracy, being founded mainly upon the customs and habits of mankind rather than upon any systematic study of what the actual necessities of the body are.