Women who eat more fruits, vegetables and protein before pregnancy may lower the risk of their child developing leukemia -- the most common childhood cancer -- according to a new study by University of California, Berkeley, researchers.

Some 276 Northern California mothers answered a questionnaire on 76 food items to reveal their overall diets in the year prior to their pregnancies. Half the women had a child diagnosed with acute lymphoblastic leukemia while the other half had children without cancer.

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 leukemia.

"It's not so much a question of did these women do something wrong, but rather, these are things you can do to help protect yourself and your child," said Christopher Jensen, a nutritional epidemiologist at UC Berkeley and lead author of the study.

The study, published in the current issue of Cancer, Causes and Control, is the first of its kind, and the authors caution that the results need to be replicated. Previous studies have looked at maternal diet and childhood cancer risk but have focused on specific foods or supplements, not overall diet.

Certain foods -- including carrots, string beans and cantaloupe -- seemed to have stronger links to lower childhood leukemia risk, according to the study.

These foods contain carotenoids, which are a source of vitamin A and have been shown to function as antioxidants in laboratory tests.

Although researchers looked at diet in the year before conception -- not during pregnancy -- they noted that other studies have shown that women's eating habits do not change much during pregnancy.

The findings are consistent with research suggesting a diet high in fruits and vegetables can help prevent adult cancers.

"The positive message here is that mothers may be able to transfer some of those benefits to their children," said co-author Gladys Block, a UC Berkeley professor of epidemiology and public health nutrition.

Between 2,000 and 2,500 children nationwide are diagnosed with acute lymphoblastic leukemia each year.

The cause of the disease -- in which the bone marrow produces too many white blood cells -- is largely unknown.

Protein, including red meat, poultry and beans, can have a protective role, too, the study suggests.

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.

"Leukemia is a very complex disease with multiple risk factors," said Patricia Buffler, UC Berkeley professor of epidemiology and head of the Northern California Childhood Leukemia Study, which includes this research. "What these findings show is that the nutritional environment in utero could be one of these factors."