Nutrients called omega-3 fatty acids, found in fish oils, flaxseed and walnuts, may start protecting a woman from breast cancer before she is even born, U.S. researchers reported on Wednesday.

Scientists found a dramatic drop in mammary cancer risk among mice whose mothers ate diets rich in the omega-3s while pregnant and nursing, according to a Louisiana State University study.

The study adds to the known benefits of omega-3s, which lower the risk of Heart disease.

And they add to a growing body of research that shows nutrition in the womb can affect a person’s health as an adult a half-century or more later.

Most Westerners typically eat far too much omega-6 and too little omega-3. This may tend to cancel out the benefits of omega-3s.

Meat, eggs, poultry, cereals, breads and most vegetable oils are big sources of omega-6 fatty acids, while the omega-3 fatty acids are found in green leafy vegetables, canola or rapeseed oil, flaxseeds, walnuts, soy oils and cold-water fish such as tuna, salmon and mackerel.

Elaine Hardman of the Pennington Biomedical Research Center at LSU in Baton Rouge studied the effects of the nutrients after reading studies that showed diets high in omega-6 fatty acids raised maternal estrogen levels, which in turn are linked to an increased incidence of breast cancer among female offspring.

“Inadvertently, we may be setting up our daughters to develop breast cancer 50 years from now,” Hardman said in a statement. She was to present her findings at a meeting of the American Association for Cancer Research in Anaheim, California.

Hardman said she worked with mice bred to develop breast cancer. Female mice were fed diets high in either omega-6 fatty acids or omega-3 fatty acids, both during the gestation period and while nursing pups.

After the daughters were weaned, one group was placed on a high omega-6 fatty acid diet, while the other was fed predominantly omega-3 fatty acids.

All female pups exposed only to omega-6 fatty acids had mammary gland tumors by six months of age.

But fewer than 60 percent of the female offspring who were nourished with omega-3 fatty acids either before birth or while nursing formed mammary tumors by the age of eight months.

Those exposed to omega-3 fatty acids both before and after birth had a tumor incidence rate of just 13 percent.

Hardman said it is not difficult to get enough omega-3 fatty acids. Fish oil capsules are usually free of the mercury contamination that worried many people, she said, as are walnuts.

“A couple of servings a week may be enough,” she said. “A quarter of a cup of walnuts constitutes one serving.”