The chemical bisphenol A (BPA), found in hard plastics, has come under great scrutiny in the past few years for negatively impacting hormonal health. BPA is an estrogen-like compound that has been proven to be an endocrine (hormone) disrupter. It is present in plastic bottles and canned food linings and is easily leached from the plastic into water and food, as this 2011 Harvard study confirmed.
Even trace amounts of BPA can affect human health. Links have been established between BPA and hyperactivity, obesity, early puberty and reproductive dysfunction. BPA has become ubiquitous in our environment. The EPA reported in 2010 that over 1 million pounds of BPA are released annually into the environment, showing up in the water and food supply and in the oceans.
BPA and Thyroid Impact
Particularly disturbing is the potential impact of BPA on infants, who are exposed to it mostly through food containers and polycarbonate bottles. In July of 2012, in response to widespread consumer pressures, the U.S. FDA banned the use of BPA in baby bottles and cups. Karin B. Michaels of Harvard Medical School commented that “infants may be particularly susceptible to BPA’s endocrine disruptive potential.”
Indeed, the endocrine disruptive potential of BPA is a complicated area of study. However, one new study has linked BPA with potentially dangerous changes in thyroid hormone levels in pregnant women, fetuses and newborn male babies.
Frederick vom Saal, a scientist studying the influence of BPA on animals and humans, explained that exposure to the chemical can be critical on the front end of one’s life where the rest of your life’s physiology is being programmed. Its damaging effects seem to be permanent.”
The damaging influences of BPA identified in the recent UC Berkeley study include its potential to decrease the level of T4 in the pregnant women. T4 is one type of thyroid hormone, known as thyroxine. Low T4 levels indicate hypothyroidism which can underlie symptoms such as weakness, fatigue, depression and higher cholesterol levels.
Healthy, normalized thyroid levels are necessary for neurological and cognitive development. Any impairment or imbalance of regular thyroid function in the fetus could theoretically impact brain development.
The Berkeley study found that higher levels of BPA in the pregnant women corresponded with their lowered levels of T4, and strangely, with higher levels of T4 in their fetuses and newborns. Study coauthor Jonathan Chevrier said this might indicate that the fetuses were overcompensating in their thyroid production due to the mothers’ abnormally lowered levels. Heightened levels of T4 indicate hyperthyroidism, or overactive thyroid, and are associated with symptoms such as anxiety, weight loss, visual problems and tremors.
While the actual long-term effects of the imbalanced thyroid levels were not detailed in the study, the overall assumption is that BPA has negative long-term influences as an overall endocrine disrupter. The sheer breadth of its presence is concerning. Studies have shown that a majority (over 90%) of American women of childbearing age have BPA present in their urine.
Mixed Views and Controversy
While the study results draw attention to the way BPA can interfere with thyroid levels, it is unclear whether the findings are cause for alarm. Chevrier insists that there is enough evidence about BPA to merit banning it entirely and urges pregnant women to be particularly vigilant in avoiding it.
“Because thyroid hormones in the mom and the children are so crucial to normal growth and development, I would say any change in the thyroid hormones is substantially of concern and needs to be looked at really closely,” explained Chevrier.
A Stanford University clinical professor of gynecology was not as convinced. Dr. Jeffery Faig called the findings “not profound.” Faig noted that a large percentage of the maternal thyroxine does not actually reach the fetus.
A researcher for the American Chemistry Council’s Polycarbonate/BPA Global Group, Steven Hentges stated that the Berkeley study did not conclusively prove that BPA exposure negatively affected the subjects’ health. “BPA is efficiently metabolized and rapidly cleared from the body,” he explained–a fact that is often raised in defense of BPA’s potential dangers. BPA’s six hour half life makes it difficult to study its long term influences.
Interestingly, the study found that the link between BPA levels and thyroid levels only affected male fetuses and newborns. There is animal research that suggests that female fetuses are more efficient at clearing BPA from the system.
The environmental presence of BPA and its association with hormonal processes remains an area of growing concern.
Here are the four most effective ways you can minimize your exposure to BPA:
1. Drink filtered tap water. This helps avoid water that has leached BPA from plastic containers.
2. Use stainless steel water bottles or certified “BPA-free” containers.
3. Avoid all canned foods, which are often lined with BPA containing resins. Favor food packaged in cartons.
4. Avoid the use of plastic utensils.
BPA is likely not the only source of endocrine disruptors. All plastics under normal conditions release estrogenic compounds. It may be wise to avoid plastics in general.