Bisphenol A and Migraines

Bisphenol A (BPA) is probably the most maligned chemical of the 21^st Century.  It is utilized in a huge number of materials, most commonly as an ingredient in the synthesis of polycarbonate plastics, where it is chemically linked by carbonate groups to form hard, transparent polymers that are used in food packaging and drinks bottles. BPA is a known endocrine disruptor (it affects human hormone levels) and stimulates estrogen production, which has led to a recent study suggesting it as a cause of migraines: powerful, debilitating headaches which affect approximately 1 billion people. Could the leaching of BPA from polycarbonate-based food packaging be contributing to the world’s migraine epidemic, as a recent study reported in the Daily Mail suggests?

The Study

The authors examined the effect of injecting quantities of BPA directly into the brains of rats, subsequently looking for symptoms usually displayed by human migraine sufferers. The rats dosed with 500 ug/kg/day of BPA were found to exhibit increased sensitivity to light and sound, decreased movement and increased startle reflexes, all of which are human symptoms of migraines. Additional testing found increased levels of estrogen in the rats, which is posited as a cause of migraines in previous work from the group.

The Outcomes

There are some points that must be taken into account before blaming BPA for migraines. Firstly, the dosing of the rats in the study, 500 ug/kg/day, is ten times higher than both the US and EU safe exposure limits. The BPA is also injected directly into the rats’ brains rather than absorbed through the typical human exposure route of consumption, further exacerbating its effects.  Finally, we must consider how much BPA are humans exposed to in real life. Estimates suggest (pdf) typical exposure levels are approximately 0.4 ug/kg/day, over 1000 times lower than the rats’ dosage in the study.  This “high dose” study is typical of those which link BPA to deleterious conditions, in that the exposure of the animal test subjects to BPA is considerably higher than typical human exposure. It is worth remembering the old adage “the dose makes the poison” – detrimental effects are likely when injecting anything into the brain at 1000 times the subject’s usual exposure.

Media Reporting

The study was only significantly reported in the Daily Mail, who failed the simplest test of providing a link to the paper for their readers.  They quote the authors plea from the manuscript to readers to remove sources of BPA from their life, without any additional author comments. To counter this, no information is provided on the leaching of BPA from plastics and any risk this provides. The typical chemical scare-story template was completed by the use of “gender-bending” to describe BPA, which is completely out of context in this story. From the reader comment section, it is clear that BPA will continue to divide public opinion. Government agencies such as the US Food and Drug Administration, The UK Food Standards Agency, and the EU Food Safety Authority maintain that BPA is safe for use in food packaging, yet the pendulum seems to be swinging towards outright national bans, despite a statement from the World Health Organisation advising that bans were “premature”. In the highly emotive area of babies’ bottles, an EU-wide ban on BPA is in effect – an example of public opinion swaying legislation in the face of scientific data. On this evidence, and in the face of continuing studies and press such as this latest offering, it may soon be the end for BPA.

L. M. M. Vermeer, E. Gregory, M. K. Winter, K. E. McCarson and N. E. J. Berman, (2013). “Exposure to Bisphenol A Exacerbates Migraine-Like Behaviors in a Multibehavior Model of Rat Migraine”. Toxicological Sciences early online view: doi: 10.1093/toxsci/kft245