Muddled communications on mercury causing consumer confusion
This is the first of a two-part series investigating the challenge of encouraging the public to eat more seafood against the backdrop of consumer fears over mercury contamination. The second part of the series will appear tomorrow.
It’s a rare occasion when representatives of industry, academia, and government all agree.
The fact that the U.S. seafood industry, an army of health experts, and the U.S. government all want to see the country’s population consume more seafood is a sign of how universal the agreement is surrounding the health benefits of seafood consumption.
But in seeking to achieve that objective, consensus often breaks down over the best way to communicate the benefits to consumers. One of the biggest points of division is the issue of mercury contamination in fish, since scientific studies on the potential harm of mercury in seafood are often conflicting and a source of frustration to consumers.
Jay Shimshack, an asssociate professor of public policy and economics at the University of Virginia and an expert in environmental and health policy, told SeafoodSource the problem lies with the way policymakers frame the message when issuing health advisories.
“Fish consumption advice is often complex and confusing. Message-framing matters a lot, and real-world constraints like affordability are as important as the true risks and benefits,” Shimshack said.
Consumers are told eating a variety of fish can be good for them, Shimshack said.
“But [they are told], ‘Do not consume some species [and be] careful not to consume too much of other species,’” Shimshack said. “Current U.S. commercial fish advisories list more than 60 species, and species names are not always consistent from one time and place to the next.”
The advisory to which Shimshack is referring, a joint list put together by the U.S. Food and Drug Administration and the Environmental Protection Agency, categorizes 60 species of fish and shellfish into “Best Choices,” “Good Choices,” and “Choices to Avoid” for pregnant women and children. The fish they advise women and children avoid eating are those commonly found high up in the seafood chain, including, tuna, shark, and marlin.
The National Fisheries Institute (NFI), which represents approximately 300 seafood companies, has publicly criticized the government’s list. NFI Vice President of Communications Gavin Gibbons told SeafoodSource, “It is long past time for FDA to review its own science and communicate with that in mind.”
“The USDA’s position on fish consumption is clear as [its] Dietary Guidelines state, 'The benefits of consuming seafood far outweigh the risks even for pregnant women,’” he said. “Meanwhile, FDA’s guidance is a mix of untested infographics and confusing lists that contradict its own research.”
Moreover, the guidance provided by both the USDA and FDA is misused by those opposed to the industry to scare consumers away from eating any seafood, Gibbons said.
“For years, the issue of mercury in seafood has been misunderstood, misreported on and used as a cudgel by unscrupulous organizations looking to misinform consumers. Activists bent on negatively impacting the commercial seafood community have promoted the dangers of 'mercury poisoning' despite an avalanche of independent science that contradicts their hyperbolic claims,” Gibbons said by email. “There are no cases of mercury toxicity from the normal consumption of commercial seafood in published peer-reviewed medical literature and activists know this but it doesn’t diminish their hyperbole at all. However, in the last five years the volume of independent science that demonstrates the benefits of eating seafood outweigh the risks has become so overwhelming these groups have become more and more of an embarrassing side show and less and less of an actual voice in reasoned nutrition discussions.”
The conflicts over the science led Margaret Karagas, a professor at the Geisel School of Medicine at Dartmouth University and chair of its department of epidemiology, to analyze the peer-reviewed literature. Her analysis offers a more nuanced interpretation of the scientific findings around mercury contamination in seafood.
Karagas performed a 2012 review of more than 80 peer-reviewed studies and concluded that the topic warranted further investigation. Some evidence showed that low levels of prenatal mercury exposure may cause early childhood neurocognitive effects. Effects on older children and adults were not clear, she said.
Acknowledging that “apparent inconsistencies” in the low-level exposure literature make it difficult to be definitive on the subject, Karagas called for further dialogue between researchers, even as she explained what lay behind the apparent inconsistencies.
“Much of the available epidemiologic literature is limited by small sample-sizes, incomplete adjustment for potential confounders, and lack of consistency across exposure media (e.g., only hair in some populations, only urine in others), which have impeded making the comparisons across studies that are necessary for refined hypothesis generation and testing,” she said.
In other words, the studies sampled too few people, varied in the parts of the body used for carrying out the tests, and did not take fully into account factors that might have skewed the test results but that have nothing to do with the study being undertaken. These problems all made it difficult to analyze and synthesize the often-conflicting results.
A risk-benefit analysis of seafood consumption was published by the Food and Agriculture Organization and the World Health Organization in a joint study in 2010. That report found some cause for concern that mercury contamination could have negative health implications, but recommended that countries acknowledge “fish as an important food source of energy, protein and a range of essential nutrients and fish consumption as part of the cultural traditions of many peoples.”
The report also acknowledged “the benefits of fish consumption on reducing coronary heart disease mortality (and the risks of mortality from coronary heart disease associated with not eating fish) for the general adult population; [and] the net neurodevelopmental benefits to offspring of fish consumption by women of childbearing age, particularly pregnant women and nursing mothers, and the neurodevelopmental risks of not consuming fish to offspring of such women.”
For these reasons, the FAO/WHO experts recommended that countries “develop, maintain and improve existing databases on specific nutrients and contaminants, particularly methylmercury and dioxins, in fish consumed in their region; [as well as] develop and evaluate risk management and communication strategies that both minimize risks and maximize benefits from eating fish.”
Equally nuanced in its conclusions is the European Union’s Food Safety Authority (EFSA) Panel, which encourages a selective consumption of seafood.
“Limiting consumption of fish species with a high methylmercury content is the most effective way to achieve the health benefits of fish whilst minimising the risks posed by excessive exposure to methylmercury,” the EFSA's Scientific Committee said in a 2015 statement.
The panel established a so-called “tolerable weekly intake,” or TWI, providing seafood consumption guidelines to protect consumers from “adverse health effects posed by the possible presence of the main forms of mercury found in food.”
However, the panel also said “average exposure to methylmercury in food is unlikely to exceed the TWI.”
In an email to SeafoodSource, CONTAM scientific officer Katleen Baert said discussions between the European Commission and E.U. countries on the latest CONTAM opinions with respect to seafood “are ongoing.”
“EFSA recommends that individual Member States consider their national patterns of fish consumption and assess the risk of different population groups exceeding safe levels of methylmercury while obtaining the health benefits of fish. This particularly applies to countries where fish/seafood species with a high mercury content – such as swordfish, pike, tuna and hake – are consumed regularly.”
Photo courtesy of Into the Blue