Butter fat consumption and exposure to bisphenol A (BPA) have both been found to be associated with increased breast cancer risk. Butter consumption during adolescence has been linked to higher breast cancer risk in adulthood. The use of butter in soups or sauces, for frying food, and at the dinner table have all been found to be associated with higher risk of breast cancer in European and North American studies. High intake of full fat dairy products such as milk and cheese was found to be a significant factor for heightened breast cancer risk among Iranian women in one study. Butter, ghee, full fat cheeses (cheddar, Swiss), and heavy cream are the most abundant sources of butter fat. Half and half, ice cream, and whole milk are also significant sources.

The endocrine disruptor BPA is one of the highest-volume chemicals produced worldwide; it can be detected in the body fluids of more than 90% of the human population. BPA is a common industrial plasticizer that leaches from food containers during normal usage, which leads to human exposure. BPA has been linked to increased to molecular changes that increase breast cancer risk in numerous studies. Even low-dose exposure to BPA appears to have developmental effects on hormone-responsive organs, including the breast. BPA has been shown to promote mammary tumor development in animal models of breast cancer. Prenatal exposure of mice to relatively low levels of BPA alters mammary gland development in ways that increase the likelihood of subsequent tumor development. Now a new study has reported that high consumption of butter by rat mothers during pregnancy heightens the mammary tumor-promoting effects of gestational exposure to BPA in their offspring.

Sources of BPA exposure

Bisphenol A is used to manufacture polycarbonate plastics found in plastic baby bottles, water bottles, and plastic containers. BPA is also found in various canned goods, where it leaches from the epoxy coatings used to prevent corrosion of can interiors. In addition to food cans, soda cans are often lined with plastic that contains BPA. BPA is pervasive in household dust and is found on thermal cash register receipts. Consumer protections with respect to BPA are weak. Bisphenol-S (BPS) is now starting to be used as a bisphenol-A substitute and has been described as safer than BPA. However, recent research suggests BPS has harmful effects similar to that of BPA.

Latest research finds butter heightens BPA's impact on rat pup mammary glands

The study referenced at the beginning of this news story was designed to investigate the potentially additive effects of concurrent gestational exposure to butter fat and BPA on mammary tumor risk in a rat model of breast cancer. To conduct the study, the authors exposed Sprague Dawley rats to various doses of BPA (2.5-2500μg per kg body weight) along with a high butter-based diet from before conception to birth. Another set of rats were exposed only to the butter diet.

BPA-induced tumor incidence and number of mammary gland terminal end buds were found to increase in the presence of the butter diet. Both results peaked at a dosage of 25μg/kg body weight BPA (among the lowest dosages studied). The authors also analyzed the expression of genes in mammary tissue samples of both the BPA (25ug/kg BW) group and the butter diet alone group. This examination determined that two specific cancer networks (involving extracellular-signal-related kinase (ERK) and androgen receptor signaling) were dysregulated, apparently through DNA methylation. These results suggest changes in gene expression during early development that predispose cancer risk. The authors conclude that BPA predisposes mammary glands in early development to higher cancer risk by dysregulating gene expression in the presence of the butter diet, potentially facilitating cancer development in adulthood.

Please see our articles on BPA and protecting our daughters from breast cancer during the prenatal period and infancy for more information.