Exposure to dioxins during pregnancy can harm the cells in a woman's breast tissue, explaining why some women have trouble breastfeeding, say University of Rochester Medical Center researchers. They believe their findings, although only demonstrated in mice at this point, begin to address an area of health that impacts millions of women but has received little attention in the laboratory. "Estimates are that three to six million mothers worldwide are either unable to initiate breastfeeding or are unable to produce enough milk to nourish their infants," said researcher B. Paige Lawrence. "But the cause of this problem is unclear, though it has been suggested that environmental contaminants might play a role. We showed definitively that a known and abundant pollutant has an adverse effect on the way mammary glands develop during pregnancy."
Dioxins are generated mostly by the incineration of waste, especially certain plastics. Most people are exposed through diet, as dioxins get into the food supply when air emissions settle on farm fields and where livestock graze.
Five years ago, Lawrence's laboratory made the discovery that dioxin impairs the normal development of mammary glands during pregnancy. However, the underlying mechanisms were unclear, as was the extent of injury and whether exposure during certain stages of pregnancy had more or less of an impact on milk production.
Now, Lawrence's team has shown that dioxin has a profound effect on breast tissue by causing mammary cells to stop their natural cycle of proliferation as early as six days into pregnancy. In tissue samples from mice, exposure to dioxin caused a 50-percent decrease in new cells.
The researchers also found that dioxin altered the induction of milk-producing genes, which occurs around the ninth day of pregnancy, and decreased the number of ductal branches and mature lobules in the mammary tissue.
The timing of dioxin exposure also seemed to be significant, the study noted. For example, when exposure occurs very early in pregnancy but not later, lab experiments showed that sometimes the mammary glands can partially recover from the cellular injury.
"The best thing people who are concerned about this can do is think about what you eat and where your food comes from. We're not suggesting that we all become vegans - but we hope this study raises awareness about how our food sources can increase the burden of pollutants in the body. Unfortunately, we have very little control over this, except perhaps through the legislative process," noted Lawrence.
An important question to answer, Lawrence said, is whether the toxic harm is occurring directly in the breast, or if it occurs throughout the entire body but has a unique manifestation in the fatty mammary tissue.
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Source: University of Rochester Medical Center
