||Disease is impairment of any function of person. The term has come to mean the sum total of perception of impairment by the person (symptoms), the disorder observed by the physician (signs), and the discernible biochemical or cellular changes (pathology). The quality and practical value of the description of disease is much improved if the cause is known, and further improved if there is a well-established and proven means to prevent or to treat the disease.
Western medicine has focused upon external causes of disease, such as injury or harmful agents. An early observation, in 19th-century Britain, was the common occurrence of scrotal cancer in chimney-sweep boys, leading to coal tars being called toxic and carcinogenic. The science of microbiology has revealed many causes of disease bacteria, fungi and later viruses. Koch, the discoverer of the cause of tuberculosis also postulated four conditions which must hold in order to link a micro-organism with a disease. One hundred years later, Koch\'s postulates are still valid, but are, of course, disregarded when convenient. Although, for example, the description of the disease tuberculosis includes the means to prevent and to treat the condition, the incidence or commonness of the disease has remained unpredictable and this suggests that factors other than the causal agent need to be taken into account.
Another group of diseases are caused by deficiencies of essential substancesâ€”for example, blood loss can lead to iron-deficiency anaemia, which is treated by stemming the loss and replacing the iron. In pernicious anaemia one fails to absorb an essential substance (vitamin B12)â€”here the absorption defect is difficult to treat and the vitamin can easily be injected to cure the disease. The attribution of diseases to dietary deficiencies is no longer scientifically supportable except in rare circumstances. Dietary disease is most commonly undernutrition or starvation or our very own Western malady, overnutrition. Disordered function of the endocrine glands can cause disease by over- or under-function.
There is still a large proportion of diseases in which the model or description does not include cause, or the means to prevent or to treat.
An examination of diabetes provides a rewarding example in interaction between human thought and doctors\' action. The name of the illness means â€˜siphonâ€™ and it was first known as the â€˜pissing evilâ€™. The frequently passed and abundant urine was found to be sweet tasting by pre-biochemical, 17th-century physicians. (Fortunately for researchers such unsavoury duties have always been well rewarded.) The abundant sweet urine is due to an excess of glucose in the blood which passes into the kidney tubule where it draws water from the person to try to achieve a â€˜normalâ€™ concentration. The excess of glucose is the prime observable phenomenon about diabetes. In the late 19th century, experimental animals whose pancreases had been removed were found to have diabetes. Insulin was discovered by Banting and Best in 1921 and came to be used to treat diabetic people. However, those who survived the acute effects of the disease developed the chronic effects which were also life threatening. Biochemical information accumulated and many Nobel prizes later a most elegant and beautiful picture of metabolic processes emerged. Diabetes proved to be a profound and pervasive metabolic disorder in which the â€˜burnerâ€™ which produces our energy seemed to splutter for many accountable reasons some of which could be set in train by an insulin deficiency. Another aspect of treatment of diabetes is by regulation of diet. Because of the excess of glucose, carbohydrates (the part of diet which includes sugars) were assumed to be â€˜badâ€™ and diabetics had to eat a diet low in carbohydrates, that is to say, a diet high in proteins and fats. This diet is similar to what was eaten by people reacting to the privations of the war and in whom a rise in heart attack rate was observed. It is also the diet which was experimentally fed to rabbits, with the same result.
The next change in thinking came with the recognition of the value of vegetable fibres in diet, derived from the observation of a low bowel cancer rate in Ugandan people who ate a high-fibre diet. This led to clinical trials of high-fibre and whole-grain-based diets as part of the treatment of diabetes. The trials proved the preventive effect of such a diet on many complications. Thus, after the discovery of insulin, the evolution of the rational treatment for diabetes was influenced only minimally by the elegant biochemical model explaining the disease. The clinical trials which revealed the information of fundamental importance were intuitively derived from the distantly related information about high-fibre diets which influenced the fashion of thinking about the effect of what we eat. Much effort has been expended on futile efforts to isolate the protective factors in grain. The high, whole-grain diet has a clearly proven therapeutic value, but the way in which it works is not known.
Western medicine has tended to emphasize external causes of disease. When, for example, the emotions are assumed to have a role in the cause or manifestation of disease there is still a trend to group such situations under a â€˜stress-related diseaseâ€™ or external heading. By contrast the classical Chinese system lists 14 causes of disease, seven external (heat, cold, dryness etc.) and seven internal (the emotions). TG
See also epidemiology; health; medicine.