A new study published in Nature Communications suggests that pregnant women who eat unhealthily during their pregnancy may be permanently altering the cells of their foetus and those of subsequent generations.

Led by post-doctoral researcher Sonia de Assis, scientists from Georgetown University used pregnant rats to investigate how a high-fat diet and one supplemented with ethinyl-oestradiol (synthetic oestrogen) affect cancer risks in future offspring.

The study showed that maternal exposure to a high-fat diet during conception increases breast cancer risks in daughters and granddaughters by 55 to 60%. A fatty diet is associated with higher levels of the female sex hormone oestrogen.

The scientists also found that excessive consumption of oestrogens during pregnancy is even more harmful as it increases breast cancer incidence by 50% — and this increased risk is passed down three consecutive generations (daughters, granddaughters and great-granddaughters). Dietary sources of oestrogen, also known as phyto-oestrogen, include soy products, flaxseeds and legumes.

‘We know that maternal diet can have long lasting effects on an offspring’s health, but this study demonstrates, for the first time, that excess oestrogens and a high-fat diet can affect multiple generations of a rat’s offspring, resulting in an increase in breast cancer not only in their daughters, but granddaughters and great-granddaughter’, said Leena Hilakivi-Clarke, study co-author and professor of oncology at Georgetown Lombardi Comprehensive Cancer Center.

‘Fatty foods are endemic in our society, and significant levels of substances that have hormonal activity similar to oestrogens, called endocrine disrupting chemicals, have been found in food and drinking water’, warned Sonia de Assis.

While the findings have yet to be confirmed in humans, the researchers of Georgetown University believe that a healthy diet during pregnancy could decrease the incidence of breast cancer; the most common cancer in the UK affecting one in eight women. The NHS advises pregnant women not to ‘eat for two’ and to avoid foods high in fat such as junk foods.

Study details

The research was conducted on two groups of pregnant rats and their babies. One group was fed a high-fat diet and the other was given an excess of oestrogen. Changes in the two groups were evaluated against the control group; a third set of rats which were kept on a healthy diet (neither high fat nor oestrogen-rich).

Even though daughters and granddaughters of the rats which were given more fatty foods were fed a healthy diet, the scientists found that they had a significantly higher risk of developing breast cancer compared to the control’s offspring.

Furthermore, the research suggests that a father’s diet can also increase the risk of breast cancer – but it is transmitted through the mother.

The scientists are confident that blood tests may reveal the inheritance of breast cancer risk, due to family history. Hilakivi-Clarke commented: ‘Our ongoing preclinical studies have found that the increase in breast cancer risk caused by in utero exposure to excess oestrogens can be reversed by drugs that reverse epigenetic marks – chemical modifications that turn genes on and off – caused by the exposure’.


    de Assis et al (2012) High-fat or ethinyl-oestradiol intake during pregnancy increases mammary cancer risk in several generations of offspring. Nat Commun. 3:1053.