Dietary fibre and large bowel cancer

There are a number of 'cancers of western civilization' common in North-West Europe, North America and Australasia which are rare in Africa, Asia and South America. The incidence of these cancers in migrant populations from Japan, South-East Asia or Eastern Europe to North America or Australia is similar to that of their newly adopted home rather than to that of their country of origin, indicating that environmental factors are more important than genetic factors in determining the incidence of these diseases. Environmental factors can be divided into those associated with culture (e.g. diet, smoking and the use of other drugs, personal hygiene) and those associated with the physical environment (e.g. climate, air pollution, geographical location) and these can be dissociated by studying groups with different cultures living in the same city. When this is done it is found that in Bombay these cancers are more common in Christians and Muslims than in Hindus and Buddhists whilst in Johannesburg they are more common in white than in Indian or black people. From information of this sort it has been concluded that cultural factors, particularly diet, are of major importance in the aetiology of these cancers.