AN EXPERIMENT IN FIRST-CLASS PROTEIN

DR. CORRY MANN : AN EXPERIMENT IN FIRST-CLASS PROTEIN

145

consumption of a protein-free diet for a few days. and then, also for periods of a few days, of the same diet plus the protein or proteins under study until the amount of each which will restore nitrogenous BY H. C. CORRY MANN, O.B.E., M.D., M.R.C.P. Lond. equilibrium is determined. Less of a superior and of an inferior protein will be required to more SENIOR PHYSICIAN TO THE EVELINA HOSPITAL FOR SICK CHILDREN, LONDON accomplish this. Such results have a quantitative character, but the experimental periods have usually With an Introduction by been too short and the conditions have often proved Sir F. GOWLAND HOPKINS, F.R.C.P. Lond., P.R.S. trying to the health of the subject, leading to unsatisfactory results. Dr. Mann made the necessary effort involved in Introduction maintaining for long periods that standardisation Dr. Corry Mann has honoured me by his desire that of daily activities which is essential for such an I should comment upon the following description experiment. Always assuming that the amount of a most interesting experiment. of protein eaten is not greatly in excess of current That proteins in different foods vary in their needs, there can be no better method of comparing nutritional or " biological " value is now generally one protein with another than that of simple replaceaccepted as a fact of practical importance. Hitherto, ment during the continuance of routine activities in respect to human nutrition at any rate, the chief conscientiously maintained. The criteria available emphasis has been laid on the relative inferiority for the evaluation of the diets were, it is true, mainly of vegetable proteins as compared with those of animal based on subjective symptoms ; for although the origin ; but Dr. Mann, as the result of careful observa- body-weight was recorded and shown to remain tions on himself, has obtained evidence which suggests constant on the favourable diets, the loss was small that there may be marked differences in value between even on the least favourable. No determinations such proteins as those of milk and meat respectively. were made of the nitrogen balance of the body. The nature of Dr. Mann’s experiment and its Dr. Mann however is a trained observer, and we results, fully described by him in the paper which may be sure that the subjective symptoms were follows, may in briefest fashion be thus summarised : accurately noted and evaluated. In considering the results attention must be given Having proved upon himself the adequacy of a selected basal diet which contained inter alia a ration to the possibility that the favourable influence of the milk ration was due to factors other than a superiority of milk and another of meat, he then omitted half of the former and found that the diet was then no in its proteins. Any suggestion that the milk proteins longer equal to his needs. On the other hand, when, are easier of digestion than those of meat can, I instead of the milk, meat containing almost the consider, be ignored. There is available evidence to show that the difference is very small and same amount of protein was removed from the diet, its adequacy was apparently maintained. inconstant. It might be urged that when milk is He holds that the most likely explanation of these removed from a dietary there will be a greater loss results is to be found in the superior nutritional value of vitamins A and D than when meat of equal protein content is removed, and that this might account for, of the milk proteins. or contribute to, the superiority of milk over meat. If this be so the circumstance is certainly one of I think however that after the removal of either, the much importance, and of special interest just now, when so much effort is being spent to secure a safe residue of Dr. Mann’s basal dietary contained sufficient national milk-supply and its proper distribution. of these vitamins for the adult body, while the Experiments dealing with the biological values of symptoms he describes as following the use of the proteins have been very numerous on animals, but unfavourable diet do not seem to have been those of vitamin deficiency. few have been made on man. Prominent among the latter are those carried out upon himself by Karl One aspect of the results may seem puzzling. In Thomas in 1909. The method used by him measured his classical experiments at Woodford which have the relative powers of various proteins to spare the established Dr. Mann’s high reputation as a student body from a loss of tissue proteins. According to of nutrition, he himself found that the addition Thomas the biological value of meat proteins taking of casein to the institutional diet of boys produced that of milk proteins as 100, is 104 ; that is to say, much less extra gain in weight and growth than did they are practically identical, the difference found a milk ration containing approximately the same being within the limits of experimental errors. Martin amount of protein. It would seem therefore at first and Robison however when describing some very sight that factors other than superiority in its proteins careful observations of their own, pointed out that must have accounted for the highly favourable the figures given by Thomas for milk were open to influence of milk in the Woodford experiment. criticism. They agreed with him however in finding Doubtless this was in part the case, for the basal that wheat proteins have for the human body a diet there was deficient in animal fats, while margarine much lower value than those of milk, but they did replaced butter. It is likely therefore that vitamins A not compare the latter with other animal proteins. and D were deficient and while the milk ration It would appear indeed that on human subjects increased them the casein ration of course did not. no satisfactory comparisons have been made ; Corry Nevertheless the Woodford results with casein do Mann’s experiment on himself is so much the more not make negative other evidence for the superiority welcome. of milk proteins over meat proteins, and as bearing Certain aspects of the experiment and its results on the present experiment it should be remembered call for comment. I think it may be said first of all that the mixed proteins in milk yield together a more that Dr. Mann did well to study the effects of the favourable amino-acid balance than is found in varying diets while continuing his ordinary avocations. casein itself when isolated from its associates. This enabled him to follow their effects during long It is a circumstance worthy of notice that the periods under normal conditions. Experiments in the subject of this experiment, when on the basal diet laboratory have generally involved the subject in the from which meat was withdrawn, maintained his AN EXPERIMENT IN FIRST-CLASS PROTEIN

146

DR. CORRY MANN : AN EXPERIMENT IN FIRST-CLASS PROTEIN

health, and activities, which though

equal to those of a large section while consuming some 60 g. of protein were

not strenuous of the public,

of which only of the so-called first-class variety. It may be asked whether this is because so much of the latter was composed of milk proteins. It should be noticed further that this apparently adequate diet contained little more than 2000 calories. In conclusion I would like to express the opinion that Dr. Corry Mann’s experiment on himself should direct attention to what may well be a very important point in practical dietetics. All will agree, however, that a final proof of the superiority of milk proteins for human nutrition must ultimately be based upon a fully controlled experiment on numerous individuals, and best on young individuals, such as that carried out so admirably at Woodford by Dr. Corry Mann It is on behalf of the Medical Research Council. much to be wished that he who conducted that investigation might be given the opportunity of extending it in circumstances equally favourable. 42 g.

Diet, experimental. Kensington, 1931, 1932, Weight 145 Ib.

1933.

_

were

The Observations of was planned with the idea value to the minimum requirements of first-class protein for an adult, with a secondary aim of comparing the protein of milk with that of another common item of an ordinary diet. Anyone who has undertaken research in experimental dietetics will realise that in an investigation of this sort the first consideration is to schedule a " basic diet " which suits the particular occupation of the person who forms the subject of the test and also that person’s basic metabolism. The basic diet so chosen must maintain the nutrition of the individual without deterioration in health, and at the same time allow him to carry out his daily occupations whether in pursuit of a livelihood or in satisfaction of recreational activities. Such a diet will vary much, both in calorie value and in composition, with different persons. The basic diet here detailed had been tested at intervals, for varying periods, during ten years and it had been found to be adequate between the years 1921 and 1931. The subject of experiment was a man of middle age. His weight was 145 lb. with a constant summer-towinter and winter-to-summer swing. His medical history for some 30 years, even under active service conditions, had been singularly uninteresting from a doctor’s His standpoint. occupation-partly sedentary-was of a routine nature for about half of each week. During the remainder of the week his work was of a more varied type and involved travelling by car or train but with little expenditure of muscular effort. With the start of the experiment in 1931 a definite amount of walking exercise was introduced. Certain distances were plotted out on the map and time-distance was logged weekly, any excess or deficiency of exercise during one week being immediately corrected in the following week. In this way an average of 15 miles timed walking exercise was maintained, while the experiment was in progress, during each week.

This experiment

setting

a

THE EXPERIMENT DESCRIBED

1. The basic diet was taken, with the additional scheduled weekly exercise, for a period of four months (Diet No. 1). Result : similar to previous experience. General health remained normal with body-weight showing a normal daily swing.

7 ,44 g. milk fat.)

(d) Contains butter. (e) Or mutton chop or minced mutton. (/) Or cabbage, or lettuce.

of milk were deducted from the diet, from each of the first two meals and 4 oz. from the 4.30 P.M. meal. This may be called Diet No. 2. 2. Ten 3

taking

ounces

oz.

147

DR. J. H. WILLIAMS : REDUPLICATION OF SECOND TRICUSPID SOUND

The

new

if only Ioz. of milk remained in the diet in addition to the small quantity of boiled milk above mentioned. In other words, the protein of milk appears to be of more value for purposes of nutrition than the protein of meat.

values may be tabled thus :-

FURTHER NOTE

Note.-The

animal protein is thus reduced from 52-88 to

438g.

This diet was given in all for six weeks. During the first five weeks there was a slow steady fall in weight, with a general deterioration in physical condition. The subject of experiment, who was quite accustomed to spend a busy day without fatigue, found that after a morning’s routine he became unusually tired by 1.30 P.M. These symptoms of deterioration becoming more troublesome in the sixth week the Diet No. 2 was discontinued. 3. The basic diet-No. 1-was resumed and continued for three months. During the second week there was a definite improvement in physical condition and normal health was rapidly regained. 4. Diet No. 3 was then substituted for the basic Diet No. 1. The items deducted to form Diet No. 3 were selected to give a value equivalent in calories to the milk deducted to form Diet No. 2, and containing about the same amount of animal protein and animal fat. The new values may be tabled thus :Deductions

,

fact

:

.

Note.-The 41-80 g.

animal protein is thus reduced from 52-88 to

was given for several weeks. The subject experiment remained fit without unusual fatigue, the physical condition remained good and the diet

This diet of

satisfied. 5. It was decided to repeat the experiment with Diet No. 2, in order to exclude neurosis. For this purpose the basic Diet No. 1 was again resumed and was maintained for three months, the general health remaining normal with a steady body-weight at the average level. 6. Diet No. 2 was resumed (vide supra). On this occasion 10 oz. of hot water were taken every night in order to exclude any possibility that the symptoms of physical deterioration, which had been previously experienced, were due to diminution of fluid intake. Result : physical deterioration, after four weeks, was again obvious. The diet-No. 2-was maintained for a full six weeks with symptoms of lassitude increasing and a total fall in weight of 2-25 lb. 7. Return to basic Diet No. 1. Slow progress for a fortnight, followed by steady recovery. SUMMARY

therefore that, for the individual the presence of a full ration of 21 oz. of milk in the diet described, which contained a small additional quantity of boiled milk in a helping of milk-pudding, enabled general health to be maintained without deterioration, even when the total protein had been reduced to 60’65g. daily and the total animal protein to 41-80 g. daily (Diet No. 3). On the other hand, a reduction of total protein to 64-33 g. and of animal protein to 43-48 g. was followed by progressive deterioration in physical condition It would

in

question,

seem

Attention is drawn to the fact that the most this schedule is the breakfast, not only from these observations but from others which have been made with diets employed during conditions of most strenuous physical exertion, that fatigue in industry would be less marked if employers of labour could offer facilities for a breakfast which is something more than a hasty and insufficient meal. Such a breakfast would contain well-balanced rations including first-class protein, adequate fat, and vitamins, without undue loading with carbohydrate, having regard to the fact that carbohydrate alone-even as dextroseis insufficient to prevent the after-effects of fatigue. There are also the considerations of climate in this country, which for the greater part of the year is colder and more moist-more productive of rheumatic infections-than the climate of those more southerly European countries where an English breakfast is considered unnecessary. that the Lastly, I would lay stress upon the milk which was used for the purpose of the experiment was milk which had been pasteurised by the low-temperature process-a process which implies adequate thermostatic control. The milk was a daily sample of the milk-supply in Kensington from the local pasteurisation plant. The source of the milk was not selected for the experiment, nor had the firm supplying the milk any knowledge at all of the

important meal in and it is suggested,

test. I know of no evidence in support of the contention that the nutritive value of milk, as a whole, or of its vitamins or of its protein, is damaged by pasteurisation to an appreciable degree. Experimental work in human nutrition is against such a claim. Many of

the wild statements, which have been made, that irreparable damage is done to the nutritive value of milk by the process of pasteurisation are prompted by an ulterior motive-to lower the charges of milk distribution. No milk is really safe that has not been pasteurised. The best milk is that which comes from a tuberculin-tested herd and which is subsequently pasteurised by the low-temperature process.

TRANSITORY REDUPLICATION OF THE SECOND TRICUSPID SOUND AS A SOLE SIGN OF CORONARY THROMBOSIS BY J. H.

WILLIAMS, M.B., B.Sc. Wales

THE patient is a well-built, very healthy looking of 54. He is a caretaker at a large institution, where his work is not heavy, consisting mainly of attending to furnace fires and the lawns and gardens. man

Before he came under my told that his blood pressure

in 1928 he had been higher than normal, and so he used to come to see me periodically to have it checked. He did not complain of any ill-health, and there was no evidence of any organic disease. The blood pressure was usually 150/90 when he came to see me, though once or twice I found it as high as 160/90. On these occasions a short period of treatment by the administration of potassium iodide brought it down to 140/90, though it had a tendency to rise again slowly. care

was