"This is the first time researchers have conducted a systematic survey of a woman's diet and linked it to the risk of childhood leukaemia," said Dr. Kenneth Olden, director of the US National Institute of Environmental Health Sciences, the body that funded the study.
Researchers at the University of California, Berkley compared 138 women who each had a child diagnosed with acute lymphoblastic leukaemia (ALL) with a control group of 138 women whose children did not have cancer. The children of all the women in the study were matched by sex, age, race, and county of residence at birth.
After comparing the women's diets in the 12 months prior to pregnancy, researchers found that the higher the intake of vegetables, fruit and protein-rich foods, the lower the risk of having a child with leukaemia.
"The health benefits of fruits and vegetables have been known for a long time," said principal investigator Gladys Block, professor of epidemiology and public health nutrition at U.C. Berkeley. "We found in this study that the protein foods group is also very important."
After further studies, the researchers discovered that glutathione - an antioxidant found in meat and legumes - was the nutrient in the protein group that had a strong link to lower cancer risk.
Moreover, the fruits and vegetables that seemed to be the most closely associated with a lower cancer risk were those that are high in carotenoids, such as carrots, string beans and cantaloupe.
Researchers also studied the use of vitamin supplements, but did not find a statistically significant link to childhood leukaemia risk.
A conference held in London earlier this month similarly drew attention to the potential importance of diet during the early years of a child's life. Organised by the charity Children with Leukaemia heard that plant foods as well as the spice turmeric may have a protective effect against leukaemia.
Dr Marilyn Kwan and her colleagues from U.C. Berkeley 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.
Leukaemia kills more children in Britain than any other disease and cases of this and some other childhood cancers in developed nations has been rising at around 1 to 3 per cent each year for the past 50 years.