Incidence rates of childhood leukaemia are significantly lower in Asia than in Western countries.
The incidence of childhood leukaemia in Britain increased dramatically during the twentieth century. The increase has mainly affected the under-five age group, in whom the risk increased by more than 50 per cent during the second half of the century alone.
Although the causes of leukaemia in children are poorly understood, modern environmental and lifestyle factors are thought to play a major role in the rising incidence. If this is the case, it should be possible to take preventive measures. But first we need to identify the factors responsible.
This is the motivation behind the conference – Childhood leukaemia: incidence, causal mechanisms and prevention – which is being hosted by CHILDREN with LEUKAEMIA, Britain's leading charity devoted to the conquest of the disease.
Professor Moolky Nagabhushan of the Loyola University Medical Centre, Chicago will present evidence that the low incidence of leukaemia in Asia is due in part to the protective effect of turmeric, a spice used widely in Asian cooking. "Some of the known risk factors that contribute to the high incidence of childhood leukaemia are the interaction of many lifestyle and environmental factors," says Nagabhusan. "These include prenatal or postnatal exposure to radiation, benzene, environmental pollutants and alkylating chemotherapeutic drugs. Our studies show that turmeric - and its colouring principle, curcumin - in the diet mitigate the effects of some of these risk factors."
In a long-running series of studies, Nagabhusan has shown that turmeric has the potential to protect against leukaemia in a variety of ways – it can inhibit the mutagenicity of cigarette smoke polycyclic aromatic hydrocarbons, radiation induced chromosome damage and it can prevent the formation of harmful heterocyclic amines and nitroso-compounds which can result from eating certain processed foods. He has also shown that curcumin irreversibly inhibits the multiplication of leukaemia cells in cell culture.
Nagabhusan says these results are confirmed in humans.
Dr Marilyn Kwan of the University of California, Berkeley will be presenting the results of another study looking at the effects of food on the risk of leukaemia. As part of the Northern California Childhood Leukaemia Study, Kwan and her colleagues set out to determine whether the foods consumed by children in early life affect their risk of developing leukaemia. They collected information on the diets of 328 children diagnosed with leukaemia and compared them with matched controls.
"We found that regular consumption of oranges and/or bananas during the first two years of life was associated with a reduced risk of childhood leukaemia," Kwan reports.
"These findings are consistent with the protective role of fruits and vegetables observed in adult cancers."
The association is thought to be due to the high vitamin and mineral content of both oranges and bananas. Oranges are rich in vitamin C, an antioxidant that may prevent oxidative damage to DNA, thus protecting against carcinogenesis. Bananas are rich in potassium, the anti-carcinogenic potential of which has been speculated upon by epidemiologists.
Whilst these papers do not address the rising incidence of childhood leukaemia in Britain, since dietary intake of both turmeric and fresh fruit are higher today than 100 years ago, they do provide important clues as to the aetiology of the disease, as well as offering up possibilities for prevention.
The increasing incidence combined with emerging concerns about the long-term effects of leukaemia treatments, make prevention a top priority.
It is hoped that out of the conference – which has attracted top international experts from Europe, America, Asia and Australia - will be born an agenda for future research. CHILDREN with LEUKAEMIA will be launching a £1m fund to support research in priority areas.