A study examining the role childhood diet plays in breast cancer has found an association between eating french fries regularly during the preschool years and developing breast cancer as an adult.

Each weekly serving of french fries girls between ages 3 and 5 consumed increased their risk of developing breast cancer as adults by 27 percent, according to researchers at Brigham and Women’s Hospital and the Harvard School of Public Health.

The association was not found with potatoes prepared in other ways.

The finding is the first of its kind and must be confirmed by other studies, said lead author Karin Michels, an associate professor at Harvard Medical School and clinical epidemiologist at Brigham and Women’s Hospital in Boston. “This is something nobody’s really looked at before. It’s really new,” she said, adding, “It could be due to chance.”

She speculated the french fries may be implicated in breast cancer because they are prepared in fats that are high in harmful trans-fatty acids and saturated fat.

The dietary survey examined the childhood eating habits of participants in the Harvard Nurses’ Health Study. To obtain information about what adult women had eaten as preschoolers, the researchers asked the mothers of participants in the nurses study to fill out questionnaires asking how often their daughters had eaten 30 different food items.

The researchers analyzed data gathered in 1993 from 582 participants with breast cancer and 1,569 women without breast cancer. The participants were born between 1921 and 1965, so their mothers were being asked to recall information from decades earlier. Michels noted these recollections may have been unreliable, especially when made by mothers who already knew their daughters had breast cancer.

Consumption of whole milk was associated with a slightly decreased risk of breast cancer, though most of the milk consumed during those decades was whole milk, Michels said.

“Only one food so distinctly stood out as being associated with breast cancer risk,” Michels said, and that was the french fries.

She said dietary influences may be more significant during early life than during adulthood, because the breast of a girl or infant is more susceptible to environmental influences than the breast of a mature woman.

Dr. Larry Norton, deputy physician in chief of the breast cancer program at Memorial Sloan-Kettering Cancer Center in New York, warned against over-interpreting the results. “I wouldn’t go out and change Americans’ dietary habits on the basis of this, but it’s certainly worth pursuing the hypothesis with additional research,” he said.

Michels said her study doesn’t prove that giving up French fries will protect women from breast cancer. But with child obesity rates rising, she said, “There are numerous reasons to avoid French fries.”