Mums-to-be may pass on cancer risk via fatty diet

Women who eat a fatty diet when pregnant could unwittingly be increasing the risk of their daughters and granddaughters getting breast cancer, research has shown.

Chronic exposure to hormone-like chemicals in food and drinking water may have a similar effect down the generations.

The findings could explain why breast cancer often runs in families even though known inherited genes account for only a small number of cases.

Researchers fed pregnant female rats a high-fat diet from before conception to the time they gave birth.

Their daughters were 55% to 60% more likely to develop breast cancer than animals whose mothers were fed a normal diet.

When the daughters eventually gave birth themselves, their female offspring were equally at greater risk of breast cancer.

The raised risk from fatty diets did not extend to the great-granddaughters of the original rats. But the impact of a hormone supplement was felt across three generations.

Pregnant rats given synthetic oestrogen in their food had daughters with a 50% higher chance of breast cancer. The same level of increased risk affected both their granddaughters and their great-granddaughters.

Chemicals with oestrogenic properties are abundant in plastics, paints, food packaging, and electrical equipment. Though they are present at low non-toxic levels, experts believe long-term exposure to such endocrine disrupting chemicals could have important biological effects on fertility and other aspects of health.

Lead scientist Sonia de Assis, of Georgetown University in the US, said: “This study suggests directions for future research in women. Could a woman’s susceptibility to breast cancer development be determined by what her grandmother ate when she was pregnant, or if she was exposed to high levels of oestrogen — perhaps unwittingly — through the environment?

“It’s easy to see how this study possibly has human health implications to be considered, since fatty foods are endemic in our society, and low levels of chronic exposure to endocrine disrupters — substances that have hormonal activity such as oestrogen — have been found in food and drinking water.”

The findings, published in the online edition of the journal Nature Communications, are believed to result from environmental effects on genes.

Exposure to certain chemicals in the womb can determine whether specific genes are switched on or off. Evidence suggests that such “epigenetic” effects can become cemented into DNA and passed to future generations.

It means gene activity can be altered by chemicals in the environment without new mutations being created.

In this case, the agent responsible appears to be oestrogen. Diet is involved because fat provides the raw material for oestrogen production in the body.