Fathers Eating Fatty Diets Increase Daughters' Breast Cancer Risk

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White lab rat shown with glass lab flasks.
White lab rat shown with glass lab flasks.Credit: Dreamstime.com

Rat fathers who eat a lot of animal fat put their daughters at higher risk of breast cancer, says a paper in Breast Cancer Research.

The study done in Brazil, albeit a small one, concluded that if fathers gorge on animal fats, their daughters had heightened risk of breast cancer compared with fathers who ate relatively more plant-based fats.   Animal fats are like butter and bacon, as opposed to vegetable oils.

Studies of paternal factors affecting breast cancer are rare. "In this study we have used a rat model to compare the impact of the consumption of high levels of animal or vegetable fat by fathers before conception on their daughters’ risk of breast cancer,” explains Thomas Ong, corresponding author.

Indeed, though just last month, another paper published in the same journal found heightened breast cancer risk in female mice if their fathers were fat. Obese fathers pairing with normal females produced female mice pups that were fat at birth and well into their childhood. "These baby mice also develop breast tissue later than usual and have an increased rate of breast cancer," the researchers wrote.

In the animal-fat rat study, the scientists fed 20 male rats a lard-based diet, 20 a diet based on corn oil and had 20 serve as controls, getting 16% of their energy from fat. The rats were then allowed to be fruitful and multiply with lady rats subsisting on standard lab rat diets. (Pellets.)

The babies were also fed a standard laboratory diet, but the scientists did not wait for them to perhaps develop cancer. Mammary tumors were induced at 50 days of age.

To calculate the breast cancer risk, the researchers measured the time it took for tumors to appear, the number of animals with tumors (the incidence) and the number of tumors per animal. They also examined tumor volume.

Obese male mice pairing with normal females produced female mice pups that were fat at birth and well into their childhoodCredit: Reuters

The results were that tumors were more robust in the daughters of all the rats who ate heavy-fat diets. But the daughters of the rats eating corn oil developed their tumors more slowly. They had fewer tumors than the daughters of rats who ate lard.

They also showed smaller tumor growth, compared with the animal-fat crowd and the controls, too.

The problem doesn't lie in gene expression, or mutation, but in changes to the RNA molecules that read the DNA. The RNA molecules can be modified by methylation, changes that can pass from generation to generation. Micro-RNA bits carrying epigenetic information from obese father mice can reach their unborn daughters.

"This suggests that the type of dietary fat consumed by fathers is an important factor influencing their daughters’ breast cancer risk,” said Ong.

Now it remains to confirm the findings in humans, and if the findings are consistent, to advise would-be fathers to go short on the butter and bacon and heavy on vegetable oils ahead of wooing and winning for the sake of procreation, if nothing else.