Seafood Mercury Concerns Subside Amid New Research | The Paleo Diet®
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Seafood Mercury Concerns Subside Amid New Research

By Christopher Clark
January 29, 2015
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Fish and other marine life have been integral to human diets since the Paleolithic era. Some researchers even speculate that these foods “made us human” by enabling the rapid expansion of grey matter in the cerebral cortex. For three million years of evolution during the time of Australopithecus, brain capacity remained constant, but then curiously doubled during a one-million-year period between Homo erectus and Homo sapiens.1 The reasons for this great expansion are not entirely known, but increased dietary omega-3from fish and shellfish was likely involved.

Fish consumption remains critically important today, but comes with complications unimaginable to our distant ancestors. Industrial pollution has greatly increased environmental mercury, much of which ends up in oceans and lakes, and finally, in small amounts, in the bodies of fish. In higher amounts, mercury is toxic and is especially problematic for developing babies. For years, the FDA was advising pregnant women to limit their fish consumption during pregnancy, but last year, they issued a draft revision encouraging prenatal fish consumption.2 This draft, which will eventually replace their previous recommendations, reflects a growing awareness, seen in the scientific literature, that fish is essential for developing babies and contains nutrients that limit, or even counter, the potentially harmful effects of mercury.

Recently published in the American Journal of Clinical Nutrition, a new study, representing 30 years of research in the Seychelles, is one of the longest and largest population studies regarding seafood and mercury.3 The Seychelles is a nation of islands clustered together in the Indian Ocean, where residents consume 10 times as much seafood as do Europeans and Americans, making it an ideal place to study the long-term impact of mercury exposure via seafood. The researchers concluded that high fish consumption by pregnant mothers, as much as 12 meals per week (the FDA recommends three), does not cause developmental problems in children.

To the contrary, fish is extremely beneficial for development, and contains special nutrients that protect against mercury. Lead author Dr. Sean Strain explained, “This research provided us the opportunity to study the role of polyunsaturated fatty acids [PUFAs] on development and their potential to augment or counteract the toxic properties of mercury.”4 Mercury is thought to damage the brain through oxidation and corresponding inflammation. Fish are rich in omega-3 PUFAs, which prevent inflammation, as opposed to omega-6 PUFAs, which promote inflammation. This was reflected in the study whereby children of mothers who had higher omega-6 blood levels performed worse on tests designed to measure motor skills.

This study builds upon an impressive body of research conducted by Dr. Nicholas Ralston and colleagues at the University of North Dakota. Ralston has demonstrated that selenium also protects against mercury toxicity and that foods with relatively higher amounts of selenium with respect to mercury, pose neither developmental nor neurological risks based on mercury toxicity.5 “This may explain,” Ralston says, “why studies of maternal populations exposed to foods that contain Hg [mercury] in molar excess of Se [selenium], such as shark or pilot whale meats, have found adverse child outcomes, but studies of populations exposed to MeHg [methylmercury] by eating Se-rich ocean fish observe improved child IQs instead of harm.”6

The vast majority of commonly consumed fish and shellfish contain far more selenium relative to mercury and many have significant amounts of omega-3 PUFAs. This means that fish and shellfish, two important components of the Paleo Diet, should not be limited nor discontinued based on mercury concerns. Whether for pregnant women, babies, children, or adults, we encourage you to keep seafood on the menu.

References

[1] Bradbury, J. (May 2011). Docosahexaenoic Acid (DHA): An Ancient Nutrient for the Modern Human Brain. Nutrients, 3(5). Retrieved from //www.ncbi.nlm.nih.gov/pmc/articles/PMC3257695/

[2] U.S. Food and Drug Administration. (June 2014). Fish: What Pregnant Women and Parents Should Know. Draft Updated Advice by FDA and EPA. Retrieved from //www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm393070.htm

[3] Strain, JJ, et al. (January 2015). Prenatal exposure to methyl mercury from fish consumption and polyunsaturated fatty acids: associations with child development at 20 mo of age in an observational study in the Republic of Seychelles. American Journal of Clinical Nutrition, 101(1). Retrieved from //ajcn.nutrition.org/content/early/2015/01/21/ajcn.114.100503

[4] University of Rochester Medical Center. (January 21, 2015). Fatty acids in fish may shield brain from mercury damage. ScienceDaily. Retrieved from www.sciencedaily.com/releases/2015/01/150121144835.htm

[5] Ralston, NV and Raymond, NJ. (November 2010). Dietary selenium's protective effects against methylmercury toxicity. Toxicology, 278(1). Retrieved from //www.ncbi.nlm.nih.gov/pubmed/20561558

[6] Ibid, Ralston.

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