Growth and health

A general introduction to a discussion on growth and health might take either of two main forms. It might review what we know about the material requirements for growth: the total energy needs, the grams of protein required to give this or that amount of soft tissue growth, the grams of calcium and phosphorus required for growth of the skeleton; it might discuss the functional importance of substances that make little material contribution to growth, and finally, sum up what we know about the inter-relation of diet and resistance to infection. These are the subjects with the details of which most of the observational and experimental work in nutrition is, at the moment, concerned. It would take days to sum up the information; and, when that had been done, I doubt whether we should be able to do more than reaffirm general principles. These general principles are already well known. The concept of a balanced diet has become part of our ‘common knowledge’. Perhaps partly because I shirked that major task, and partly because I think it is good, now and then, to lay aside the microscope and look at things with the naked eye, I have chosen the second approach. In very general terms I am going to ask what we mean by good growth and health and what the one has to do with the other. In experimental work with animals most often weight increase is taken as if it were synonymous with growth; less often growth is defined as increase in one or more linear dimensions. Obviously increase in weight may be increase in bone or muscle or fat or merely water or some combination of any or all of these; and some linear dimensions may be just as difficult to interpret. But suppose we had some complicated technique combining weights and measures and isotope studies and specific gravity of the body, what would it tell us about growth? It would be no more than a means to a crude chemical analysis without killing the subject, and, by itself, it would be just as interesting or as sterile as any other chemical analysis. Before we can get up any real interest in the result we must know what changes in the structure and composition of the body mean in terms of some standard of value. What is value in growth? Why do we say this animal or person is well grown and that is not? We mean a great deal more, I think, than merely that the one is bigger or heavier than the other. The term well grown and the attitude of mind behind it imply some target of performance which we consider to have been approximated or missed. In an attempt to clarify that idea, I have built up an argument in picture form. In the first place we must go back to the basis of growth, which depends on nature and nurture, but we should not require either complex genetical concepts or the refinements of chemistry to make the argument plain. The fundamentals of genetics, or all of them that need concern us here, have been known for thousands of years; they are part of everyday language, everywhere. ‘Like begets like’; ‘like father, like son’; ‘what is bred in the bone …’; ‘you cannot make a silk purse out of a sow's ear’: these and similar clichés exist in all languages, sometimes in quaint forms, but with the same meaning. Even primitive man must have recognized the sometimes astonishing resemblance of child to parent, and even so-called primitive races of mankind have long practised systematic selection and breeding of their domestic stock. It is equally true that there has long been an awareness of merit in human reproduction. The ancient Greeks, and even earlier civilizations, had clear views on eugenics; and the same awareness, the same urge to ‘good breeding’ certainly persists in full force, and sometimes in strange forms, at the present day. I do not know whether, or to what extent, Plato's plans for human stud farms materialized, but modern and better informed people accept similar ideas. We have no galaxy of clichés about nurture, which is not difficult to understand. It is still impossible to disentangle the effects of different components of the environment, especially in human populations where they can seldom be varied or controlled independently, and where cause and effect are so liable to be confused. For instance, tailors were, at one time, perhaps still are, accepted as of poor physique. But that is not because tailoring interferes with growth that is, in any case, already past, but because the relatively unfit gravitate to occupations that require relatively little physical strength. But better and worse diets were certainly distinguished and are, to some extent, embodied in racial beliefs of one kind and another. Perhaps the attribution of the peculiar virtues of the English to the eating of roast beef may enjoy a scientific rebirth with the ascent of the ‘animal protein factor’ to its present prominence in experimental work. The effect of nurture on the concrete and visible expression of nature has, in the past, received too little attention at the hands of geneticists and plant and animal breeders. Let us review briefly what nurture can do to inhibit the expression of nature and what the significance of that inhibition may be. Baur (1911) has described two dandelion plants, one grown high in the Alps on poor soil and in the cold, the other in the warm and fertile plain. If the dandelion were an important food plant, the verdict would be that the big, succulent plant is the better. But consider a different plant. Exactly the same occurs if edelweiss is transported to a warm and fertile garden. It loses its grey colour and white hairs; it stretches out and becomes green and leafy, the flower looks different; in fact an uninteresting plant. The Alpine is the plant that is prized. This little story has two morals. The first is that if one has seen a plant, or animal, only in one environment, all one knows about its genetic constitution is what it can do in that environment and not what it may do or not do in any other. The second is that the terms good and bad, better and worse, as descriptions of plants or animals, are not absolutes, but are valid only in relation to environment, and that they imply some criterion of value which may be utilitarian or aesthetic or both. This is now, of course, well recognized in relation to crop production. For instance, a very large chapter in the history of Canadian agriculture is the story of the search for varieties of wheat that would survive the dry, cold climate of the prairies, that would grow and ripen in the short growing season, and that would resist indigenous diseases. This is not yet so well realized in regard to animals, so let us look at what the wrong nurture can do to animal nature. McMeekan^apos;s (1940a-c, 1941) papers on the growth of pigs show (Pl.1, fig.1) how a well-bred or ‘improved’ pig grows. One can see the change in shape as the animal grows from birth to the approved 200 lb bacon pig. In shape, the original wild pig at the fully grown stage is much more like the improved pig at birth than at maturity. The important thing is that the characteristics that are valued by the pig farmer, who is going to sell pork or bacon, are those which develop last. The most prized parts of the pig are the loin and hind-quarters. And the quality of the joints depends on the distribution of lean and fat. The same is, of course, true of beef and mutton. A series of most important experiments, started in Dr Hammond's laboratory in Cambridge and continued in New Zealand, was made to test the effect of feeding on the development of the carcass of pigs and lambs. They showed in the most striking fashion that poor feeding not only stunts, but also delays indefinitely and, if continued long enough, permanently prevents, the full development of the later-developing and best parts of the carcass. If a bacon pig is underfed for half its short life and then given a full ration, this ‘low–high’ pig will certainly put on weight. But the important point is that skeleton and muscle will not grow as they would have done if they had had the opportunity at the right time, and the extra food will be used mainly to lay on fat (McMeekan, 1940c, Pl.27). The moral of this is that growth potential is not a thing that one can speed up and slow down, as one can accelerate or retard a chemical process, and get the same result in the end. If one does not use the full potential all the way along one does not get full development. One may get the same ultimate weight but one will get a carcass that is different in shape and in composition. Now we have an idea of what is implied by a well-grown pig. If it is also fat, that should be ‘finish’ added when the correct framework of bone and muscle has grown to the desired size. It may seem that it is a long step from bacon pigs and prime beef or mutton to man. Not so long a step perhaps. An old diagram, drawn by Stratz and widely reproduced, e.g. by Brody (1945), of the change in shape that occurs in man during growth shows that, in essentials, the change is the same as in the pig. Development is from the cephalo-thoracic region forwards and backwards and the hind-quarters mature last. If the rate of growth is sufficiently slowed the adult is not only small but underdeveloped, with normal or nearly normal size head, moderately retarded trunk and relatively short legs. Let me make quite clear at this stage that this does not necessarily mean that all small adults are underdeveloped. There are still all too many whose small total height is attributable to rickets in infancy. Often they are people with a high growth potential whose parents were quite simply ignorant of any special need for material for calcification of bone. But, apart from these, and possibly differences of build due to variations in endocrine balance, it would be expected on general principles that children continuously underfed would grow into underdeveloped adults. If this is so, a difference in body proportions should be demonstrable in association with differences in height wherever persistent differences in nurture are known to exist. And that, I submit, can even now be confirmed by observation in any city in this country, if one looks for it. The graph depicting social gradient in height of schoolchildren between 1927 and 1935 which is to be found in Food, Health and Income (Orr, 1937) does not represent the extreme difference at that time. Selection of data for poor urban council schools gave a curve that was still lower. I tried to find recorded data to test my hypothesis about difference in shape, but unfortunately leg length is a measure not often recorded. At that time I found only one set of data (Hansen, 1932) from which similar conclusions had been drawn and which quoted, from an earlier observer, that ‘Full typical development in man implies, relatively to body length, short torso, long arms and long legs’. It is a set of measurements of Copenhagen school children, which included not leg length but sitting height, and deduced that taller children had relatively longer legs and were relatively heavier. (The difference would probably have been more obvious if leg length had been measured.) Anyway, when the Carnegie U.K. Dietary and Clinical Survey was planned at the Rowett Research Institute in 1937, cristal height (height from the floor to the highest point of the iliac crest), as a measure of leg length, was included in the measurements to be made. Statistical analysis of the data, divided into groups according to expenditure on food, has only recently been completed and the gist of the results is as follows. I am indebted to Mr Quenouille of the Statistical Department, University of Aberdeen, for the information. The three measurements, height, cristal height and weight were analysed to find out which predicted most reliably the expenditure group to which a child belonged. It was found that cristal height was consistently better than total height for indicating expenditure group and, for age groups under 12, height was better than weight. In other words, the difference in leg length was relatively greater than that in either total height or weight. That is to say, this idea was statistically confirmed as far as social gradient is concerned; and confirmed at a time when that gradient was already rapidly diminishing. But I shall not transgress into Dr Weir's field and talk of secular changes in growth at this stage. Instead, I am going to suggest that the consciousness of this difference is universal and so fundamental that it colours both our literature and our art. In romantic literature, the hero and heroine are always long limbed. If the heroine is small, and of course some readers like her that way, it is always expressly stated that she is ‘perfectly proportioned’. Conversely, if the villain has to be large, he is also coarse, brutish or gorilla-like. The same is true in art. One will admit I suppose that advertisements, because they aim to use the most popular imagery, might be a good mirror of popular taste. High-class fashion journals with an extreme length of and does the same for both and One may think some of the with of and there is, in no great difference in A very small increase in the of leg length to total height has a effect on Conversely, a may be also by the of the to the as or the he people with short legs and them fat, with results which suggest the ‘low–high’ pig. to my that there is a general awareness of a growth target which is because it means full development. quite no because the later-developing the most in their and of shape become the of The is whether this is aesthetic a of or whether it has some other And that us to It would of course be to suggest that all people are necessarily or that all small people are It might and it is, that there is no adult than the from the of some of our But that is an argument that both If they have the of the because they are then it a that so many of the and that they are not as well as when they do grow If I on these I am given one of two The first is that, of course, they are the of and the of the of the The that for mankind was to this association of between selection and The it with as from the idea that of the some and not merely to survive in a given environment, it may have done much to and to either agriculture or human in any of means this is true from the of the soil to the of the to be to a large of the to the of a environment is so to have quite about it. The second I get is that size has no in and that what we is It is difficult to this school of to an of strength. If they mean in the general of to and or similar that, I should think, is of and rapidly social and, in any in that is so on that it is I am of an attempt to physical by The of in of with and with and The idea in the of at of these to be that the child is of a a and Obviously if one plants out into a cold and they will more than plants in the if they can be so But that does not mean that they are or less It simply means that the is a more environment, for a than the garden. We full to the dandelion and the It all depends on whether we them well grown or and if they are when Before we this of it is perhaps to ask whether height, is of any in work. An of it is in and that a high of have from It would be of great interest to have of the and weights of distinguished I have been able to find only one a very one of the and their There are three the the and the and The of weight in the first two is on the about one and a half and in the about In the performance is with and weight and height are also with weight is the is by height, but in the height has a but not effect on as far as this height is a where the is and the performance relatively but where speed and are required in to muscle then height is with much for of strength. also there is that height, weight and performance are For instance, the for of to the has been consistently than that for the and that for the at to still That of course, that these were from of these of and as height and weight the other way those who the height test and were on were, on the than those and, in of when the of the the same is We have then, so no the that better development greater physical What other in the present of can be data are for the general and it is difficult to disentangle the of all the social of and to as well as and, on the for and at about the same rate growth, it is difficult to whether inhibition of growth, has any effect on I think be from animal but I to as may be from human is by the history of In both where diet to the of the growth of children, the of in an increase might be to in and as If we take the two the of the environment by of and of were greater in the second than in the but the effect on especially in was much Not only was the but the from the and to the the of racial not in the general but was seen only and It looks as if which underdeveloped also interferes with the which or to The of this is by the of both rate and and when we have we so often do not have age and that may have a effect on For instance, during the as often in as in but in was that in were similar and, if only rate and not also were it might be that there was no difference between the two populations at But the rate was probably by and the by the probably the of the It that similar of for much in poor children to and of the in Let us look at rate for the same children in the Carnegie U.K. Dietary Survey on the physical measurements were made We find the children less than the short at all there is specific for we might that the constitution built up when the of growth is is, in some way, to that with inhibition of growth, The of then is that the and children and adults are by and health by of where we can get a picture in which the can be at partly We cannot go much in this analysis at It would be of the interest to be able to the history of and people in terms of and and of I can sum up the general picture in terms of social which a general difference in standard of This shows that, for those who have in there is a difference of in mean age at between the highest and social An analysis of the in terms of of is not to this and I will the argument with one The ‘low–high’ first in growth and, when it is then well than will be I think, has its human when with size of and some of is only growth has It is, of course, most obvious where adult is not That is one of The other is that of the well-grown person who is and in and then back into the physical of an and the of a but to about as much as he when and shows the of in terms of the of life The moral is not quite the same for both The of the well-grown can no doubt be to and but I doubt whether that of the can be by the of a which a The real is good feeding in eating and in sum up we have seen that there is a basis for and people in that of growth and to a of I have that there is an awareness of merit in this which is in literature and art. It is also in the utilitarian of selection for This is up to a but even where and are of little or no there is still a to the and still more the small person he is If one is one may get by on the basis of a but that may have its This may be of social importance and it would be interesting to have an analysis of or of in relation to physical of data of the Carnegie U.K. Clinical and Dietary of data of the Carnegie U.K. Clinical and Dietary age at of who have completed of life from age at of who have completed of life from The of The of