Mercury in the Diet: An Update on the Health Risks of Fish Consumption in Europe

The European Food Safety Authority (EFSA) has conducted a study on the consumption of fish and seafood that may contain mercury and has updated its guidance on such consumption as well as its risk assessment for public health. While fish provides beneficial nutrients such as omega-3 fatty acids, exposure to methylmercury—the most dangerous form of mercury in seafood—is associated with harmful effects on the brain and neural development of fetuses and children.  

An EU-wide study

The study was commissioned by the European Commission, as some Member States are updating their recommendations regarding the frequency of consumption of fish and seafood that may contain mercury residues, as well as a review of the maximum permissible mercury concentrations in various species of fish and seafood. These include large predatory fish such as sharks, swordfish, and tuna, which feed on smaller fish, leading to the accumulation of mercury in their bodies over the course of their lives. An initial survey was conducted in the 27 EU member states, as well as in Iceland and Norway, in the spring of 2023. The second survey was carried out in ten countries that had updated their dietary guidelines, as well as in five others that had not, to allow for comparison. The surveys included a higher proportion of pregnant women, since fetuses are most exposed to mercury through their mothers.  

Frequency of consumption and amount consumed

First finding: 60% of respondents reported consuming fish and seafood. About one-third of them (34% of adolescents and adults, and 33% of pregnant women) consume fish species with the highest levels of mercury contamination three times a week or more. How much fish and seafood should consumers eat? Most health authorities in EU countries recommend one to two servings per week of fish and seafood species with the highest mercury levels (i.e., 1 mg of mercury per kilogram of fresh fish), or three to four servings of species with the lowest levels (i.e., 0.5 mg/kg or 0.3 mg/kg of fish). Pregnant women are advised to minimize their exposure to mercury by choosing smaller fish.  

A risk-benefit balance to consider

EFSA notes that the health benefits of eating fish include the development of cognitive and immune functions in infants and a reduced risk of cardiovascular disease in adults. However, excessive exposure to methylmercury is harmful and is particularly associated with delayed brain and neural development in fetuses and young children. However, while risk managers may consider measures to reduce exposure to methylmercury, the potential health benefits of fish consumption should also be taken into account. The survey also assessed respondents’ knowledge of various health benefits and risks associated with seafood consumption, in order to gauge the extent to which nutritional recommendations are understood and followed. Overall, the consumers surveyed were much more aware of the health benefits (about 5 out of 10) than the risks (about 1 out of 10), but mercury was the contaminant most often cited in these foods. While many consumers reported having heard of the recommendations in their country and taking them into account in their food choices, it appears that other factors—such as taste, cost, and the desire for a healthy diet—have a greater influence on changes in eating habits.   The report highlights significant disparities among European countries and consumer groups (adolescents, adults, pregnant women), both in terms of consumption and awareness of the recommendations. This information, along with the strategies outlined in the report, could prove useful to various national public health authorities in communicating with consumers on this topic.