GUEST BLOG: You are what you eat! | Breast Cancer UK

GUEST BLOG: You are what you eat!

Published 17 Sep 2018

We live in a world permeated with plastic. Although some types of plastic are not thought to be harmful, there are questions over the risk to human health from others. In particular some plastics contain a chemical called bisphenol A (BPA), which has been the subject of much debate.

Exposure to BPA is most commonly from leaching into foods from packaging, but it is also found in thermal paper and dental sealants (1). As a result of this, BPA can be found in the urine of most people across the world (2).

Bisphenol A is a chemical that looks a bit like oestrogen. It has been shown to be an endocrine disrupting chemical, which can mimic oestrogen (3-5). BPA has been suggested to be linked with several human health outcomes such as breast cancer, altered response to hormones, type 2 diabetes, obesity and cardiovascular disease (6-10). In our previous work, we have shown that in human populations, and in human cells in the laboratory, exposure to BPA is associated with altered expression of some genes, including the oestrogen receptor beta and the oestrogen related receptor alpha genes (11; 12). This may be one reason why exposure to BPA may have adverse health consequences, although this remains to be determined.

Previous work from other researchers has suggested that it is possible to reduce your personal exposure to BPA in less than a week by avoiding potential sources of this chemical (13). These studies however used a small number of participants in a laboratory setting, where all food and drink was provided, which would be difficult to follow in real life.

To see whether it was possible to influence how much BPA you are exposed to in a real world setting we at the University of Exeter have embarked upon a 2 year citizen science research project with local ‘A’ level students to answer this question (14). Our rationale was that since there is a question over the health impacts of exposure to BPA, we should have a choice in whether or not we are exposed to it, which we currently do not.

Over 100 students took part in the study, whereby following a workshop on how to design and implement a real scientific study, they designed a set of simple guidelines designed to reduce exposure to BPA, and followed this for 7 days. The students gave a blood and a urine sample before and after the intervention, to assess whether they had less BPA in their systems after following the diet. They also kept detailed records of everything they had eaten or drunk over the 7 week period, so they could assess how well they had stuck to the diet as a group.

We found that even when the students followed the diet exactly, and tried very hard to minimise their exposure to this chemical, it was nearly impossible to do so. 85% of students had measureable BPA in their urine at the beginning of the study, and the number of students demonstrating urinary BPA and the level of BPA found did not change over the study period. This suggests that based on our evidence, it is not possible to have any control over how much BPA you are exposed to in your environment.

We also asked the students to tell us their experiences of following a BPA-reduction diet. The results of this were striking. 90% of participants said they had found the diet restrictive and 70% of students told us that they would find it very difficult to follow a reduced BPA diet long term.

When we assessed why following a BPA free diet was so difficult, we found three potential reasons. Firstly students found it very difficult to avoid BPA because it is present in so much packaging, products are very poorly labelled so it was difficult to tell by eye which foodstuffs were likely to contain BPA and this resulted in people having to spend much more time to source plastic free foods which had impacts on their lifestyle and shopping habits.

In the real world, even if a “BPA reduction” diet was able to cause a drop in exposure, people would not follow such a diet because of the restrictions it placed on them. 

Our overall conclusions were that it was not possible to take control of our own exposure, and even if we could it would not be sustainable. We suggest that a ban on BPA in packaging or items likely to come in contact with foodstuffs, or at least better labelling of potentially BPA containing foods would make it easier for people to make an informed choice.

If you would like to support the University of Exerter Medical School in this endeavour, please support our Change petition. 

For more information on BPA see Breast Cancer UK’s Bisphenol A webpage


Written by Lorna Harries, Associate Professor in Molecular Genetics, University of Exeter Medical School,


Twitter: @miRNAgirl @ExeterMed

Breast Cancer UK does not endorse any products or any opinions expressed by our guest bloggers.  The blogs are the personal opinions and endorsements of the blogger and not necessarily reflective of Breast Cancer UK views.  If you have questions about the blog, please contact



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