A high-fat diet during pregnancy could affect the risk of breast cancer for generations, say scientists at Georgetown Lombardi Comprehensive Cancer Center. They found that feeding female mice a diet high in fat derived from corn oil substantially increased the risk of breast cancer in three generations.
"It is believed that environmental and life-style factors, such as diet, plays a critical role in increasing human breast cancer risk, and so we use animal models to reveal the biological mechanisms responsible for the increase in risk in women and their female progeny," said the study's senior author, Leena Hilakivi-Clarke.
A high-fat diet is linked to excess inflammation, and a number of epidemiological studies — studies that examine the cause of disease in specific populations — made a connection between inflammation and risk of cancer, she says.
Earlier studies found that mice that eat a high-fat diet when pregnant have female offspring that are at increased risk of breast cancer. This study found that if pregnant mice were switched to a high-fat diet during their second trimester — the period of time in the fetus when the mechanism forms that transmits genetic information from one generation to another — breast cancer risk is also raised in "great granddaughers."
A gene screen revealed a number of genetic changes in the first (daughter) and third (great granddaughter) high-fat mice generations, including several genes linked in women to increased breast cancer risk, increased resistance to cancer treatment, poor cancer prognosis and impaired anti-cancer immunity.
The researchers also found three times as many genetic changes in third generation than first generation mammary tissue between high-fat diet progeny and the control group's offspring.
"The soil in the breast, so to speak, remained fertile for breast cancer development in our high-fat experimental mice," Hilakivi-Clarke says.
The amount of fat fed to the experimental mice matched what a human might eat daily, says Hilakivi-Clarke. In the study, both the control mice and the mice fed chow with high levels of corn oil ate the same amount of calories and they weighed the same.
"But our experimental mice got 40 percent of their energy from fat, and the control mice got a normal diet that provided 18 percent of their energy from fat," she says. "The typical human diet now consists of 33 percent fat.
"Studies have shown that pregnant women consume more fats than non-pregnant women, and the increase takes place between the first and second trimester," she says.
"Of the 1.7 million new cases of breast cancer diagnosed in 2012, 90 percent have no known causes," she says. "Putting these facts, and our finding, together really does give food for thought."
The study was published in Breast Cancer Research.
According to breastcancer.org, diet is believed to be responsible for up to 40 percent of all cancers, and many experts believe that the increase in fat in American diets since the 1970s is at least partially responsible for the increase in breast cancer.
A 2014 study published in the Journal of the National Cancer Institute found that fat, particularly saturated fat, is associated with a higher risk of breast cancer.
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