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Toxic metal exposure during pregnancy

27 January 2022

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Toxic metal exposure during pregnancy

Reported by Victor Lovic, CSaP Policy Intern and Jessica Foster, CSaP Communications Coordinator

On 12 January 2022, Dr Caroline Taylor, Senior Research Fellow at Bristol Medical School, University of Bristol, delivered CSaP’s first Future Leaders Fellows Seminar of the year. As a nutritionist and dietitian, she presented her work on the lifestyle and environmental factors that cause exposure to toxic metals in pregnancy and childhood. Dr Taylor’s project aims to evaluate NHS guidance on foods to limit or avoid during pregnancy and to provide an evidence-base for the guidance, including information on exposure to toxic metals from certain foods.

What foods contain toxic metals and why is it so important?

Dr Taylor explains that pregnant women are a vulnerable group since toxic metals can cause damage to the fotus in utero, which can have long-lasting impacts on the child's growth, development, and life chances. The NHS therefore provides guidelines on foods that can contain elevated levels of toxic metals, namely certain fish (mercury) and game/game birds (lead). There is potentially a need for guidance on rice due to it potentially containing elevated levels of arsenic. However, Dr Taylor points out that the current guidance is not based on up-to-date evidence. The most recent biomarker data for toxic metal exposure in pregnant women in the UK is from the early 1990s, and Dr Taylor emphases that overall exposure levels have changed since then. Furthermore, the data on what pregnant women are eating during pregnancy are sparse. Dr Taylor raises the question of whether we should even be using the current guidelines if they are not based on up-to-date evidence. Her work therefore aims to address this “evidence gap”. Dr Taylor also argues that by emphasising the risks of fish consumption, without also communicating the benefits, the current guidance can put women off eating fish altogether. This matters since fish provides certain nutrients essential to fetal development.

“They are reducing their consumption, which is not what we would like to see.”

Dr Taylor is interested in how women obtain information, and whether they follow the guidance they receive. Her project consists of a mixed methods observational study, including surveys and interviews with both midwives and postpartum women. In a later stage of the study, she will recruit women in the early stages of pregnancy and conduct a quantitative study, monitoring biomarkers alongside more in-depth dietary work. Among other things, her initial findings indicate that while pregnant women do not avoid fish completely, they do reduce their fish consumption during pregnancy, and do not meet the recommended goal of eating at least two portions of fish per week. As for midwives, Dr Taylor found that they are generally knowledgeable about the guidance, but showed some evidence of misinformation with regards to some types of fish.

The seminar was then followed by a discussion involving academics, humanitarian aid workers and policy professionals. One participant asked: how do the harms from toxic metal exposure from eating fish, compare to the harms from not eating fish during pregnancy? Dr Taylor stressed that this question is subject to major academic debate, and she has not yet found evidence - in the data from the 1990s - to suggest any adverse health effects from low level toxic metal exposure, and instead observed some benefits from an increased consumption of fish. She therefore believes it is reasonable to say that for developed countries, at least where exposure levels are generally relatively low, the benefits of eating fish outweigh the harms from toxic metal exposure.

Another participant highlighted the potential trade-off between the level of detail contained in the guidance, and the subsequent compliance with that guidance. It could be argued that if women are presented with very accurate and detailed information about toxic metals in food, they may be less compliant with the guidelines, than if they were presented with a simple clear message. This is especially relevant to parts of the population who may struggle to maintain a healthy diet in the first place, for example refugees or other recipients of humanitarian aid. Dr Taylor agreed that her study was not fully representative of populations worldwide, or even of the UK, and that further study was needed to address the more specific needs of these different populations.

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The UKRI Future Leaders Fellowship scheme supports talented people in universities, businesses, and other research and innovation environments. It also allows universities and businesses to develop their most talented early career researchers and innovators or to attract new people to their organisations, including from overseas. Learn more here.

Jessica Foster

Centre for Science and Policy, University of Cambridge

Victor Lovic

Imperial College London

Dr Caroline Taylor

The University of Bristol