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Canola Oil May Affect Breast Cancer Risk

Study Shows Potential Benefit for Offspring When Canola Oil Is Consumed During Pregnancy
By
WebMD Health News
Reviewed by Louise Chang, MD

Nov. 18, 2008 -- Could the type of oil a woman consumes during pregnancy influence her daughter's breast cancer risk years later?

Early research in mice suggests that it might -- and that pregnant women may be better off choosing canola oil over most other vegetable oils.

Canola oil has more omega-3 fatty acids and less omega-6 than other widely used cooking oils.

"We showed that canola oil in the maternal diet during pregnancy and nursing reduced the risk for breast cancer in babies for up to five months after birth," researcher W. Elaine Hardman, PhD, of Marshall University School of Medicine, tells WebMD.

The research was presented today in Washington D.C. at the American Association for Cancer Research's Seventh Annual International Conference on Frontiers in Cancer Prevention Research.

Canola Oil vs. Corn Oil

"Corn oil has 50% omega-6 and almost no omega-3, while canola oil has 20% omega-6 and 10% omega-3," Hardman says. "Flaxseed oil is 50% omega-3, but you wouldn't want to cook with it. It tastes pretty bad. Canola is about the best cooking oil out there in terms of omega-6 to omega-3 ratio."

In the newly reported study, the mothers of mice genetically engineered to develop breast cancer were fed diets that contained either 10% canola oil or 10% corn oil for several weeks prior to breeding up until the time their offspring were weaned.

Following weaning, the offspring were fed the corn-oil rich diet.

Throughout the study, the female mice born to the mothers fed corn oil had more breast tumors and bulkier tumors than the mice born to mothers who followed the canola-oil diet. They also had tumors in more mammary glands.

This was particularly significant because on a regular diet the genetically engineered mice could be expected to develop breast cancer by 6 months of age, Hardman says.

But mice aren't people, and the findings fall far short of proving that women can protect their unborn daughters from breast cancer or increase their daughters' risk by choosing a particular cooking oil, American Cancer Society nutritional epidemiologist Margie McCullough, ScD, tells WebMD.

"This finding is intriguing, but many important questions remain," she says.

Omega-3 vs. Omega-6

There is increasing evidence that exposures in the womb may affect risk for a wide range of diseases later in life, but this has not been proven.

And since cancers usually occur in humans late in life, a study examining the impact of gestational and early-life nutritional exposure on cancer could take 50 or 60 years, McCullough says.

But Hardman says studies targeting gene expression in humans may help researchers learn more about the impact of pre-birth exposures on cancer risk much more quickly.

Her study identified 40 separate genetic changes in the mammary glands of the canola-fed mice, some of which have been identified with suppressing tumor growth.

She adds that there are many other good reasons that people should try to maximize the amount of omega-3 in their diets and reduce omega-6.

Studies suggest that both long-chain omega-3 fatty acids, found primarily in fatty fish, and short-chain omega-3 fatty acids, like those in canola oil, help protect against cardiovascular disease.

"Switching from corn to canola oil might have benefits in terms of reducing cancer risk, and it certainly couldn't hurt," Hardman says.

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