Giving infants oranges and bananas regularly may halve their risk of developing childhood leukemia, suggest the results of a new study.

And a diet containing the curry spice turmeric may also be protective - accounting for the differences in childhood leukemia rates between east and west - says a leading scientist.

Children who ate oranges, orange juice or bananas between four to six times a week during their first two years of life had a significantly reduced risk of developing the cancer, revealed the observational study by US researchers.

Previous studies on childhood leukaemias have not examined the effects of the overall diet in this way, focusing more on possible risk foods like cured meats.

"Our study is unique, and we have elucidated a significant protective association with the consumption of oranges, bananas and orange juice," said Marilyn Kwan, an epidemiologist at the University of California, Berkeley.

However, she cautioned that without carrying out a random controlled trial, it is difficult to predict exactly how protective eating these fruits may be, or to make firm public health recommendations. But in her study, she said "there was a 50 per cent reduction in risk".

The evidence for oranges and bananas, and turmeric in preventing leukaemia was presented at Children with Leukaemia's international leukaemia conference in London, UK, on Thursday.

Oranges and bananas may protect against childhood leukaemia because they are a rich source of vitamin C, which is an antioxidant. They could act by reducing oxidative DNA damage, and so stop the initiation of cancerous processes.

Bananas are also rich in potassium. Animal studies have indicated that potassium stabilises DNA and can reduce rates of mutation.