Mercury: the benefits outweigh the risks

Published: 19-Aug-2014

Every government that has assessed the risk to consumers of seafood-related exposure to mercury has concluded that the benefits outweigh the risks. But will the public be convinced?

This summer, any potential concerns about mercury in seafood have been put to rest in both the United States and the European Union. The only other known geographies to raise the issue and dispel any fears were Australia and New Zealand back in 2011. Food Standards Australia New Zealand (FSANZ) kicked off a more specific approach to mercury advisories rather than the blanket recommendations to avoid seafood that dominated the discussion and drove consumers away from the category. FSANZ concluded: “People can safely eat 2–3 servings a week of most types of fish. However, because of the presence of higher levels of mercury in some fish, there are a few types you should limit in your diet, especially if you are pregnant.”1

United States

In June, the US Environmental Protection Agency (EPA) and the US Food and Drug Administration (FDA) released their highly anticipated draft updated advice, “Fish: What Pregnant Women and Parents Should Know”. It represents a revision of the controversial advice, “What You Need to Know About Mercury in Fish and Shellfish”, which was published more than 10 years ago and has been accused of stimulating a reduction in fish intake and, thus, a reduction in EPA and DHA intake.2,3

The revision is intended to “encourage pregnant women, those who may become pregnant, breastfeeding mothers and young children to eat more fish and to eat a variety of fish from choices that are lower in mercury”, as well as align with the 2010 Dietary Guidelines for Americans, which recommends that “women who are pregnant or breastfeeding consume at least 8 and up to 12 ounces of a variety of seafood per week, from choices lower in methyl mercury”.

In addition to providing the following advice, there is an accompanying FAQ that provides greater detail, particularly regarding different types of fish and their associated mercury levels:

  • eat 8–12 ounces of a variety of fish a week
  • choose fish lower in mercury
  • avoid four types of fish: tilefish from the Gulf of Mexico, shark, swordfish and king mackerel
  • when eating fish you or others have caught from streams, rivers and lakes, pay attention to fish advisories on those bodies of water
  • when adding more fish to your diet, be sure to stay within your calorie needs.4

In 2009, it appeared that the US was well on its way to revised advice when the FDA released a draft risk assessment and benefit report titled: “Report of Quantitative Risk and Benefit Assessment of Commercial Fish Consumption, Focusing on Fetal Neurodevelopmental Effects (Measured by Verbal Development in Children) and on Coronary Heart Disease and Stroke in the General Population“.5 According to the report, “The results of our quantitative risk and benefit assessment are generally consistent with research reported in recent years in the scientific literature”. In other words, the benefits outweigh the risks.

Consuming a variety of seafood in the amounts recommended outweigh the health risks associated with methyl mercury

In 2010, the Dietary Guidelines for Americans reported: “Moderate, consistent evidence shows that the health benefits from consuming a variety of seafood in the amounts recommended outweigh the health risks associated with methyl mercury, a heavy metal found in seafood in varying levels.”6 However, despite being included in the Dietary Guidelines for Americans, the recommendations of the report did not lead to an updated FDA seafood recommendation. The report was rumoured to be seen as a unilateral move by FDA, but the EPA governs pollutants and has traditionally been consulted for FDA guidelines. As a result, it may have taken five years for this current draft to see the light of day.

European Union

In July, the European Food Safety Authority (EFSA) published its “Scientific Opinion on Health Benefits of Seafood (Fish and Shellfish) Consumption in Relation to Health Risks Associated with Exposure to Methylmercury”.7 Similar to the US EPA and FDA, EFSA concluded that children and adults alike should try to consume at least two servings of seafood per week.

In its opinion, EFSA;

  • reviewed the role of seafood in European diets
  • evaluated the beneficial effects of seafood consumption in relation to health outcomes and population subgroups previously identified by the FAO/WHO Joint Expert Consultation on the Risks and Benefits of Fish Consumption and/or the CONTAM Panel as relevant for the assessment; these include the effects of seafood consumption during pregnancy on children’s neurodevelopment and the effects of seafood consumption on cardiovascular disease risk in adults
  • addressed which nutrients in seafood may contribute to the beneficial effects of seafood consumption
  • considered whether the beneficial effects of seafood consumption could be quantified.

Relevant to EPA and DHA, EFSA concluded the following:

  • seafood provides n-3 long-chain polyunsaturated fatty acids (LCPUFA) and is a component of dietary patterns associated with good health
  • most European food-based dietary guidelines recommend (a minimum of) two servings of fish per week for older children, adolescents and adults to ensure the provision of key nutrients, especially n-3 LCPUFA; recommendations for children and pregnant women refer to the type of fish and are also based on safety considerations (that is, the presence of contaminants); seafood provides the recommended amounts of n-3 LCPUFA in most of the European countries considered
  • consumption of about 1–2 servings of seafood per week and up to 3–4 servings per week during pregnancy has been associated with better functional outcomes of neurodevelopment in children compared with no seafood; such amounts have also been associated with a lower risk of coronary heart disease (CHD) mortality in adults and are compatible with current intakes and recommendations in most of the European countries considered
  • the observed health benefits of seafood consumption during pregnancy may depend on the maternal status with respect to nutrients with an established role in the development of the central nervous system of the foetus (such as docosahexaenoic acid [DHA] and iodine) and on the contribution of seafood (relative to other food sources) to meet the requirements of such nutrients during pregnancy; no effect of these nutrients on functional outcomes of children’s neurodevelopment is expected when maternal health benefits of seafood (fish and shellfish) consumption requirements are met; the health benefits of seafood consumption in reducing the risk of CHD mortality probably result from the content of n-3 LCPUFA in seafood
  • quantitative benefit analyses of seafood consumption during pregnancy and children’s neurodevelopmental outcomes, and of seafood consumption in adulthood and risk of CHD mortality, have been conducted, but are generally hampered by the heterogeneity of the studies that have investigated such relationships.

Risks can be mitigated by consuming a variety of seafood and/or consciously choosing species that are low in mercury contamination

The good news for consumers is that every government that has assessed mercury exposure as it relates to seafood has concluded that the benefits, a large portion of which are derived from EPA and DHA consumption, outweigh the risks associated with mercury exposure. Those risks can even be mitigated by consuming a variety of seafood (rather than the same thing every day) and/or consciously choosing species that are low in mercury contamination. This is important because consumers in many developed countries have slowly started to consume less fish as a result of the fears raised by governments and NGOs in the past — and the public health impacts are potentially severe going forward. What remains to be seen is how well the message will get out to consumers.

References

1. www.foodstandards.gov.au/consumer/chemicals/mercury/pages/default.aspx.

2. www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm393070.htm.

3. www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm351781.htm.

4. www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm393070.htm#QAs.

5. www.fda.gov/Food/FoodSafety/ProductSpecificInformation/Seafood/FoodbornePathogensContaminants/Methylmercury/ucm088758.htm.

6. www.cnpp.usda.gov/Publications/DietaryGuidelines/2010/PolicyDoc/PolicyDoc.pdf.

7. www.efsa.europa.eu/en/efsajournal/doc/3761.pdf.

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