Mothers who eat fish and other foods rich in omega-3
fatty acids during pregnancy and while nursing may reduce
the risk of breast cancer in their daughters by as much
as 40 percent, a new study of mice found.
The researchers also found that feeding female offspring
a diet rich in omega-3 fatty acids after weaning reduced
their risk of breast cancer by 40 percent.
And consuming omega-3 fatty acids through foods or
supplements at any point in life can reduce the rate for
breast cancer in female offspring significantly, said
lead researcher W. Elaine Hardman, an assistant professor
at Louisiana State University's Pennington Biomedical
However, eating omega-6 fats, which are commonly found
in Western diets, could increase female offsprings' risk
of breast cancer, according to the study, presented Wednesday
at the American Association for Cancer Research annual
meeting in Anaheim, Calif.
Both omega-6 and omega-3 fatty acids are essential
for good health. But in Western diets, the amount of omega-6
fatty acids is much greater than omega-3 fatty acids.
Omega-6 acids are found in meat, eggs, poultry, cereals,
breads, baked goods, most vegetable oils and margarine,
the researchers said.
Sources of omega-3 fatty acids are fish, especially
tuna, salmon and mackerel. They're also found in canola
and flaxseed oils, soybeans and nuts.
"In mice genetically programmed to develop breast cancer,
we found that if we fed omega-3 fatty acids to the mice,
we could prevent them from developing cancer," Hardman
Hardman's team compared the rates for breast cancer
in the offspring depending upon how much omega-6 fatty
acids or omega-3 fatty acids they and their mothers consumed.
All the mouse pups exposed only to omega-6 fatty acids
-- in the uterus, while nursing and after weaning -- developed
mammary gland tumors by six months after birth, which
was expected, according to the presentation on Wednesday.
However, less than 60 percent of the female offspring
with diets rich in omega-3 fatty acids either in the uterus
or after weaning developed mammary tumors by eight months.
Hartman speculated that because omega-3 fatty acids
reduce the amount of estrogen, which is important in mammary
gland development, this helps reduce cancer risk. "Somehow
changes are going on in the breast tissue of the mice
before they're born that makes a difference in their risk
for developing breast cancer later on," she said.
Hartman said people need to include more omega-3 fatty
acids in their diet. "Particularly pregnant women need
to eat more fish or take an omega-3 supplement to help
reduce the risk of cancers in the next generation," she
One expert said this study may be relevant to humans.
"Does this prove the same is true in humans? By itself,
no. But in the context of all we know about dietary fats,
hormones and health outcomes in people, it is very suggestive,"
said Dr. David L. Katz, associate clinical professor of
public health at Yale University School of Medicine.
"I generally encourage my patients to increase their
intake of omega-3 fatty acids, and emphasize this in particular
during pregnancy and breast-feeding," added Katz, director
of the university's Prevention Research Center.
Katz noted that cancer typically develops slowly, often
over decades. So, tracing the root causes, or tracking
down all the clues to prevention, can be a challenge.
"In this case, mice are providing an important clue, and
teaching a lesson I believe we should heed," he said.