November 18 (HealthDay News) -- Women whose mothers consumed canola oil during pregnancy and breast-feeding may be less likely to develop breast cancer than those whose mothers consumed corn oil, a new study suggests.

Researchers fed pregnant and lactating mice a diet high in either corn oil, which contains 50 percent omega-6 polyunsaturated fats, or canola oil, which contains only 20 percent omega-6 polyunsaturated fats. Canola oil also has a much greater percentage of omega-3 polyunsaturated fat -- 10 percent compared with 0.5 percent in corn oil.

The study, expected to be presented Tuesday at the American Association for Cancer Research's annual conference, found that pregnant and lactating mice fed the corn oil diet gave birth to females with a greater risk of developing breast tumors than those who ate the diet higher in canola oil.

If further studies confirm the findings in humans, health officials may advise that pregnant and lactating women substitute corn oil with canola oil.

"Physicians started telling us in the '50s and '60s to take the saturated fat out of our diet and use unsaturated," said study author Elaine Hardman, an associate professor of biochemistry and microbiology at Marshall University School of Medicine, in Huntington, W.Va. "The unsaturated fat we went to was mostly corn oil, and that's about the time some of these hormonally influenced cancers started going up."

The study could have wide-reaching implications for both men and women. "Most of the time, the same things influence breast and prostate cancer, because they're both hormonally sensitive, so the same things that impact breast cancer risk also increase prostate cancer risk and the reverse," Hardman said.

But some experts advised against people changing behavior until unanswered questions are resolved.

"Is it gestation or is it lactation, because that's a pretty big difference," said Dr. Alan Astrow, director of the division of hematology and medical oncology at Maimonides Medical Center in Brooklyn, N.Y. "Before you make a blanket recommendation that has an impact on the entire population, you have to be on very solid ground."

Still, some researchers believe that pregnant and lactating women have nothing to lose by switching to canola oil.

"Some populations that eat a lot of fish consume a lot of omega-3, and there doesn't seem to be any detrimental health impact," said Hardman. "It reduces inflammation, which is also beneficial, so there are a number of beneficial things, and we don't know of anything that's prohibitive."

SOURCES: W. Elaine Hardman, Ph.D., associate professor, department of biochemistry and microbiology, Marshall University, Huntington, W.Va.; Alan Astrow, M.D., director, hematology/oncology, Maimonides Medical Center, Brooklyn, N.Y.; Nov. 18, 2008, presentation, American Academy of Cancer Research annual conference, Washington, D.C.