Fatty acids and mercury in seventy seven species of commercially available finfish in the United States

Dennis P Cladis, Purdue University

Abstract

Finfish are consumed across the United States and constitute an important part of the American diet. However, seafood consumption can be a tenuous topic, with supporters highlighting the health benefits of eicosapentaenoic acid (EPA, C20:5n3) and docosahexaenoic acid (DHA, C22:6n3) and opponents emphasizing the neurotoxicity of methylmercury. Because all fish contain varying amounts of EPA, DHA, and methylmercury, the need for clear and unbiased information is essential to alleviate the confusion experienced by many consumers and empower them to make informed decisions regarding seafood consumption. As the market changes and more fish originate from aquaculture sources, where diets are controlled, consumer intakes of EPA, DHA, and methylmercury are changing. Thus, the goal of this project was to examine fatty acid and methylmercury content in 77 commercially available finfish species commonly consumed across the U.S. EPA and DHA are important for the development of neurological function and eyesight in fetuses and infants, as well as heart health and the retention of cognitive abilities in aging populations. In accordance with these benefits, fatty acid profiles were determined for all collected species. EPA plus DHA content varied widely both within and between species. The fatty acid profiles of farmed species differed markedly from those of wild-caught species. Farmed species, including channel catfish, salmon (Atlantic and Chinook), and sturgeon (green and white), exhibited high concentrations of saturated fatty acids, monounsaturated fatty acids, and n-6 fatty acids. These differences stem from the lower costs associated with incorporating these fatty acids into farm-fed diets as compared to EPA and DHA. Some farmed species (rainbow trout, salmon, and sturgeon) were found to contain high levels of EPA and DHA, though the ratio of EPA plus DHA to other fatty acids was generally lower in farmed species than wild-caught species. In contrast to the health benefits offered by EPA and DHA, methylmercury exposure may adversely affect neurological development. For most adults consuming moderate amounts of fish, methylmercury is not a significant health hazard. Fetuses and developing infants, however, are considerably more sensitive to the neurotoxic effects of methymercury. Therefore, pregnant and nursing women should exercise caution when consuming seafood. The second half of this project examined the mercury content of all finfish collected. Total mercury content was low in most species, including salmon, Alaskan pollock, Atlantic cod, tilapia, channel catfish, and pangasius/swai, which are among the top ten species consumed in the U.S. Total mercury content was also low in all farmed species studied, though wide variations were still observed within and between species. In order to keep blood mercury levels below the USEPA RfD of 0.1 μg/kg bw-day, 27 species examined in this study should be avoided by sensitive populations. In addition, swordfish (1107 ppb) and king mackerel (1425 ppb) contained mercury levels above the FDA Action Level of 1000 ppb, meaning that consumers are not being adequately protected from high mercury species entering the marketplace.

Degree

M.S.

Advisors

Santerre, Purdue University.

Subject Area

Food Science|Toxicology|Surgery|Nutrition|Aquatic sciences

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