The Dietetic Factor in Disease.

NZMJ, 1924.

A paper read at the Otago Division of the British Medical Association in April, 1924, by STUART MOORE, B.A., M.D., M.R.C.P., Lecturer on Clinical Medicine, Otago Medical School.

Most diseases to-day are regarded as due to bacteria and other living causes. We have studied these so intently, and know so much about them, that we naturally regard them as the most important causes of disease. I would remind you that it is claimed that there is really no such thing as a cause—phenomena which result are due to constellations of earlier conditions. We should remember this, even while we continue for convenience sake to speak of causes. Medical men are asking to-day which is the more important—the soil or the seed? Certain it is that if we are to study the beginnings of disease we must study the soil, for the study of disease merely from the viewpoint of living causes cannot bring us to a period earlier than the moment of infection. The importance of the soil, however, is well known. Witness racial and individual immunity, and the manner in which healthy dogs and certain men, tend to be immune even to vermin. Witness also the wide-spread distribution of pathogenic germs, etc., within and without the bodies of the healthy.

The drift of medical opinion is to study the soil. In this, which is more important, heredity or environment? Man has been subjected to a process of natural selection through biological ages, and should therefore, in the absence of sudden and violent changes in environment, be fitted by heredity to hold his own. Therefore, though both health and disease result from the interaction of heredity and environment, we should study environment, and, particularly, we should ask what, if any, are the sudden and violent modifications of environment to which man has recently been subjected? The answer to this question is “civilisation”.

Civilisation and social organisation have been described by Spencer as super-organic evolution. In social evolution we see development from the simple to the complex at work. The same thing can be seen in the development of the mind of the individual, for civilisation is not hereditary. (Nevertheless it must be admitted that the greatest hope of proving the possibility of acquired characteristics being hereditary lies in a study of the mind.) Each one of us is born into the world at a stage of civilisation which is lower than that of any savage tribe to-day, and each one of us has to acquire during his own life-time the civilisation into which he is born, and which is developing around him. It is here we have the growing point of organic evolution. Lower in the scale of development the organism has very largely lost its plasticity and primitiveness and become rigid through specialisation. Our civilisation is a recent thing, for I would remind you that civilisations have waxed and waned on this world. We have had a succession of biological experiments made, and this succession of experiments has been rendered possible only through the fact that civilisation is not hereditary. The acquirement of civilisation by the individual is a delicate and complex process, and many of us suffer as a result from some degree of neurosis. So common is this that it is said that no one is perfectly sane.

Modern civilisation—the development of the industrial era—has exposed us to sedentary occupations, to fatigue, poisonous exhalations, overcrowding, monotony of employment, etc., but, in addition, we have experienced what is probably the most violent, sudden and unnatural modification of diet to which man has ever been subjected in the course of his evolution.

I would suggest the following list of the more important causes of disease in order of merit:—(1) Dietetic error (and errors in dress); (2) educational errors, and emotional stress and strain; (3) poisons of industry; (4) errors in exercise, of deficiency, of excess, fatigue; (5) erros in ventilation, lighting, climate; (6) heredity; while (7) vice, and (8) filth determine exposure to infection.

One and two are specially related, for dietetic errors can cause neurosis, and neurosis often causes dietetic error. It is perhaps a question which of these two results of civilisation is the more important. Heredity is rendered more important than it would otherwise be by the interference of civilisation with natural selection both by preserving the unfit, and destroying the fit.

The thesis I would lay before you for consideration to-night is that the most important factor in the preparation of the soil for disease, and in the production of disease is dietetic error.