A recent US study finds that dietary carotenoids and the antioxidant glutathione appear to be important contributors to this effect.
Acute lymphoblastic leukemia (ALL) is the most common childhood cancer, and the second most common cause of mortality in American children aged between 1 and 14 years, with between 2,000 and 2,500 children nationwide diagnosed with the disease each year. The cause of the disease, in which the bone marrow produces too many white blood cells, is largely unknown.
But recent research suggests that the disease can originate in utero.
As such, scientists at the University of California, Berkeley in California set out to investigate whether the maternal diet may be an important risk factor for ALL.
Some 276 Northern California mothers answered a questionnaire on 76 food items to reveal their overall diets in the year prior to their pregnancies.
After comparing the responses, researchers found that the higher the intake of vegetables, fruits and foods containing protein, the lower the risk of the women's children developing leukaemia.
"Among nutrients, consumption of provitamin A carotenoids and the antioxidant glutathione were inversely associated with ALL," report the researchers led by Christpher Jensen, who published their findings in the August issue of Cancer, Causes and Control, (vol. 15, no. 6, pp. 559-570(12).
Protein, including red meat, poultry and beans, can also have a protective role, the study shows. A protein called glutathione in these foods is an antioxidant and plays a role in the synthesis and repair of DNA, as well as detoxification of certain harmful compounds.
This latest study builds on mounting evidence that regular consumption of fruit and vegetables can help prevent the onset of a raft of chronic diseases in humans.
The fruit and vegetables that appear to do the best job are dark green leafy vegetables, yellow/orange fruits, citrus fruits and cruciferous vegetables.
With obesity and heart disease rates rising - according to the World Health Organisation (WHO), heart disease kills more people around the world than any other disease - governments are finding themselves weighed down by rapidly mounting health bills.
Looking for strategies to improve the health of populations, many have launched a series of national health guidelines reaching out to the consumer to encourage them to consume '5 a day' fruit and vegetables.
Advice to eat a specific quantity of fruit and vegetables has its roots in the UN agency WHO that in 1991 started recommending a minimum intake of 400g fruit and vegetables a day. One portion of fruit and vegetables is 80g, so five portions add up to 400g.
The WHO advice - adopted by several national governments - is based on a wide range of international different studies that have shown consistently that populations with a high intake of fruit and vegetables have a lower incidence of heart disease, some cancers and other health problems.