Public health guidance on cardiovascular benefits and risks related to fish consumption

Environmental Health, Oct 2007

Historically, concerns with fish consumption have addressed risks from contaminants (e.g., methylmercury (MeHg), and PCBs). More recently public health concerns have widened in appreciation of the specific benefits of fish consumption such as those arising from polyunsaturated fatty acids (PUFAs) in fish oil. Fish contains varying levels of PUFAs and MeHg. Since both address the same health outcomes (in opposite directions) and occur together in fish, great care must be exercised in providing public health guidance. Mozaffarian and Rimm in a recent article (JAMA. 2006, 296:1885–99) have made a strong case for the beneficial effects of PUFAs in reducing the risk of coronary heart disease, but at the same time, have also broadly discounted the increased risks of coronary heart disease posed by MeHg in fish, stating that "... among adults... the benefits of fish intake exceed the potential risks." This conclusion appears to be based on an inaccurate and insufficiently critical analysis of the literature. This literature is re-examined in light of their conclusions, and the available and appropriate public health options are considered.

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Public health guidance on cardiovascular benefits and risks related to fish consumption

Alan H Stern 0 1 0 Department of Environmental and Occupational Health, University of Medicine and Dentistry of New Jersey - School of Public Health , 683 Hoes Lane West, P.O. Box 9, Piscataway, NJ 08854 , USA 1 Division of Science, Research and Technology, New Jersey Department of Environmental Protection , 401 E. State St., Trenton, NJ 08625 , USA Historically, concerns with fish consumption have addressed risks from contaminants (e.g., methylmercury (MeHg), and PCBs). More recently public health concerns have widened in appreciation of the specific benefits of fish consumption such as those arising from polyunsaturated fatty acids (PUFAs) in fish oil. Fish contains varying levels of PUFAs and MeHg. Since both address the same health outcomes (in opposite directions) and occur together in fish, great care must be exercised in providing public health guidance. Mozaffarian and Rimm in a recent article (JAMA. 2006, 296:1885-99) have made a strong case for the beneficial effects of PUFAs in reducing the risk of coronary heart disease, but at the same time, have also broadly discounted the increased risks of coronary heart disease posed by MeHg in fish, stating that "... among adults... the benefits of fish intake exceed the potential risks." This conclusion appears to be based on an inaccurate and insufficiently critical analysis of the literature. This literature is re-examined in light of their conclusions, and the available and appropriate public health options are considered. - Background During the past 15 years or so, public health concerns regarding fish consumption have tended to focus mostly on the risks associated with contaminants such as methylmercury (MeHg) and PCBs in fish. More recently, recognition of the general and specific nutritional benefits provided by fish, particularly polyunsaturated fatty acids (PUFA, omega-3 fatty acids (n-3 fatty acids) has appropriately widened the public health focus to include the public health benefits of fish consumption. The potential for both risks and benefits arising from the same food source begs for an overall assessment and ultimately a balancing of risks and benefits in public health guidance. This is all the more so because the major potential health risks of concern, neurodevelopmental effects and cardiovascular effects are precisely the areas where the potential benefits may also occur. This unusual state of affairs means that great care must be exercised in providing public health guidance. It also places a considerable burden on those who would advocate significant changes in existing guidance. In their relatively recent review paper in JAMA [1], Mozaffarian and Rimm make a strong case for beneficial effects of fish-based polyunsaturated fatty acids (PUFA) per se, particularly with respect to their apparent reduction in the risk of coronary heart disease. However, I believe that they did not give adequate consideration to the increased risks of coronary heart disease posed by the MeHg in fish, and their broad conclusion that "... among adults... the benefits of fish intake exceed the potential risks" therefore constitutes inappropriate and potentially misleading public health guidance. Discussion The case that Mozaffarian and Rimm present for the beneficial effects of PUFAs in providing protection against coronary heart disease is seen most strongly in the studies represented in Figs. 1 and 2 of their paper. However, their analysis addresses only part of the public health issues connected with fish consumption. A closer analysis of their data raises serious questions about whether their analysis of the cardiovascular risks and benefits of fish consumption take both PUFAs and methylmercury into account as opposed to merely addressing PUFA intake in isolation. Many of the data in the studies they analyze reflect studies in which subjects consumed purified fish oil. To the extent that some of these studies, in fact, reflect fish intake, it is not clear that they also reflect significant MeHg intake. Higher levels of PUFA intake (in studies of fish consumption) do not necessarily reflect increased fish intake and, by extension, do not necessarily imply higher levels of MeHg intake, but may simply reflect, instead, intake of fish species with higher PUFA content. Oily fish (i.e., those high in PUFAs) are not characteristically also high in Hg. This can be seen in the data for commonly consumed species of fish presented in Table 2 of the Mozaffarian and Rimm paper and shown here (minus catfish and trout, which are not ocean fish) in Figure 1 (author's rendition). This figure shows that fish with high PUFA content are not particularly high in Hg, and the fish with the highest Hg concentration (shark, swordfish, tilefish) do not have particularly high levels of PUFA. It is also worth noting that these particular species of fish do not account for a significant portion of national fish consumption [2]. Thus, it is likely that for studies analyzed by M (...truncated)


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Alan H Stern. Public health guidance on cardiovascular benefits and risks related to fish consumption, Environmental Health, 2007, pp. 31, 6, DOI: 10.1186/1476-069X-6-31