Nutrition and cancer - global and African perspectives: a focused update.

The burden of cancer worldwide is predicted to almost double by 2030 to nearly 23 million cases annually. The great majority of this increase is expected to occur in less economically developed countries, where access to expensive medical, surgical and radiotherapeutic interventions is likely to be limited to a small proportion of the population. This emphasises the need for preventive measures, as outlined in the declaration from the United Nations 2011 High Level Meeting on Non-communicable Diseases. The rise in incidence is proposed to follow from increasing numbers of people reaching middle and older ages, together with increasing urbanisation of the population with a nutritional transition from traditional diets to a more globalised 'Western' pattern, with a decrease in physical activity. This is also expected to effect a change in the pattern of cancers from a predominantly smoking and infection dominated one, to a smoking and obesity dominated one. The World Cancer Research Fund estimates that about a quarter to a third of the commonest cancers are attributable to excess body weight, physical inactivity and poor diet, making this the most common cause of cancers after smoking. These cancers are potentially preventable, but knowledge of the causes of cancer has not led to effective policies to prevent the export of a 'Western' pattern of cancers in lower income countries such as many in Africa.