Cancer isn’t a single disease like whooping cough or mumps. The causes of cancer will therefore vary depending upon which organ is affected and which of the many different types of cells within that organ have undergone abnormal and uncontrolled division so that they invade the rest of the tissue, and later spread to other tissues within the body. The causes of cancer in a particular cell type are usually multifactorial and may well have been triggered by the interaction of more than one factor.

As the world becomes more complex so do the factors in the environment which may cause cancers. Over exposure of a group of people to some particular aspect of the environment may cause a higher incidence of the cancer.

Often co-carcinogens, two or more factors working together, multiply the effect of any one of the carcinogens considered separately. Thus cannabis increases the incidence of oral cancer, cannabis plus tobacco makes the risk considerably greater and cannabis plus tobacco plus alcohol makes the risk quite unacceptable.

A bad diet may well be a co-factor for many types of carcinoma without it necessarily being the principal cause or even such an important cause that its correction would alter the disease. For instance breast cancer is more common in the better fed, and the better fed tend also to have the opportunity and means to drink more alcohol. The underlying cause of the cancerous change in the breast cells is not the bacon and eggs, nor the double whisky but these factors play on her oestrogen levels and her genetic susceptibility of her cells to the oestrogen.

By all means encourage people to have a healthier diet. It will reduce heart disease in an appreciable number. It is likely to lessen the incidence of some carcinomas, but it is not going to empty our cancer wards.

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