Giving infants oranges and bananas regularly may halve their risk of developing childhood leukaemia, 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 leukaemia 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,” says Marilyn Kwan, an epidemiologist at the University of California, Berkeley.
However, she cautions that without carrying out a randomised controlled trial, it is difficult to predict exactly how protective eating these fruits may be, or to make firm public health recommendations. But she notes that in her study “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.
Kwan and colleagues studied 328 children under 15 who had developed leukaemia and matched controls. Questionnaires were given to each child’s mother on the child’s eating habits between birth and age two. Nine food groups were discussed, including: hotdogs, hamburgers, vegetables, apples and grapes, oranges and bananas, and carbonated drinks.
Two previous studies have found that eating cured meats like hotdogs or luncheon meats increased the risk of brain tumours and, to a lesser extent, leukaemia in children. However, the new study did not confirm this link.
Kwan believes that diet between birth and two could be crucial. “We think it might be a critical window of exposure,” she told New Scientist. “There are a lot of developmental processes occurring during that time.”
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.
Turmeric may also protect against childhood leukaemia, suggests Moolky Nagabhushan, a cancer research scientist at Loyola University Medical Centre in Chicago, US. He and colleagues in India have shown protective effects of the yellow spice’s main active component – curcumin – in a long-running series of studies. And curcumin is now undergoing initial safety testing in humans.
Childhood leukaemia rates are much lower in Asia than in western countries – and this could be due to differences in diet. The cancer is the most common childhood cancer in the west, afflicting at least one child in every 100,000. But in India, if affects only 1 child in 1,000,000. The consumption of turmeric is high in India – some estimates suggest each adult eats an average of 3 to 5 grams a day.
Nagabhushan’s work has shown that curcumin and other turmeric extracts can block the mutagenic effects of cancer-causing agents called polycyclic aromatic hydrocarbons from smoke emissions. In animal studies, it inhibited the formation of stomach and skin tumours. And curcumin can also mop up cellular molecules involved in tumour development.
Curcumin is a powerful antioxidant he says. “They put so many antioxidants in food – but instead of artificial antioxidants, they could use this,” he told New Scientist. He suggests it could even be used in baby foods after strict safety testing.
Kwan’s work has been accepted for publication in the November issue of the American Journal of Epidemiology.