Fish oil supplements linked to reduce breast cancer risk

By: Sharon Kirkey, Canwest News Service

A new study suggests that women who take fish oil supplements have a lower risk of developing the most common type of breast cancer.

Women who take fish oil supplements have a lower risk of developing the most common type of breast cancer, new research suggests.

The study, described as the first of its kind, involved 35,016 postmenopausal women, ages 50 to 76, living in western Washington State. All the women, who were healthy at the start of the study, filled out questionnaires about their use of non-vitamin, non-mineral "specialty" supplements.

After six years of follow-up, 880 women developed breast cancer. Researchers found a 32-per-cent reduction in breast cancer risk among women taking fish oil.

Of the 15 supplements that the researchers looked at — including black cohosh, dong quai and soy, supplements women sometimes take for menopausal problems such as hot flushes — "the only one that was associated with breast cancer risk was fish oil," said lead investigator Emily White, an epidemiologist at the Fred Hutchinson Cancer Research Centre in Seattle.

The results held for ductal breast cancer, the most common type of the disease, but not for lobular cancers.

"To find that it reduced a specific type of breast cancer adds a little support to the association," White said.

She cautioned that it's premature to promote fish oil for breast cancer prevention. The risk reduction was modest, in terms of the amount, though it is statistically significant, White said, meaning it was unlikely to have occurred purely by chance.

But the study provides support for the idea "that the omega-3 fatty acids that are found in fish oil might be beneficial for breast cancer. We already know they might be beneficial to cardiovascular disease," White said. Fish oil primarily contains the omega-3 fatty acids DHA and EPA.

"I think eating fish that are high in these same omega-3 fatty acids, such as salmon, is probably a good health behaviour for cardiovascular disease, and maybe for breast cancer," White said.

"It's safer to try to get these nutrients from diet."

Omega-3 fatty acids help fight inflammation, and evidence is accumulating that cancer might be related to inflammation. Inflammation leads to cell turnover, and cell turnover gives cells the chance to accumulate genetic errors that lead to cancer, White said.

"This is a little piece of the puzzle that anti-inflammatory drugs or dietary factors such as eating fish might be beneficial for chronic disease," she said.

The study's main limitation is that it relied on women to report what supplements they were taking. As well, people who take supplements tend to have healthier lifestyles.

However, the finding held after the researchers took into account family history of breast cancer, age at first birth of a child, alcohol consumption, physical activity and other risk factors for breast cancer.

The report will be published Thursday in the journal, Cancer Epidemiology, Biomarkers and Prevention.

An estimated 23,200 women in Canada will develop breast cancer this year, and 5,300 will die from the disease, according to the Canadian Cancer Society.

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