The myth that fish put kids at risk persists, with help from “experts” who ignore the evidence.
We hope that new findings serve to drive a stake through the heart of this stubborn myth ... but won't hold our breath.
For example, the August, 2014 Consumers Report (CR) magazine urged young children and pregnant/nursing women to avoid canned tuna (see “Mothers Misled by Tuna Tirade
In both cases, the editors did this despite the absence of any evidence of harm to American kids from seafood consumed by them or by their pregnant/nursing mothers.
Instead, tests commissoned by Consumers Report simply indicated that some brands of canned tuna sometimes contain somewhat more mercury than the average amounts found in U.S. goverment tests.
In a response to Consumer Reports, the FDA explained the rationale for a recent change to the guidelines for maternal and child seafood consumption that it issued jointly with the EPA in 2004:
“Based on a review of the latest science, we have concluded that it is possible for pregnant and breast-feeding women, and women who might become pregnant, to increase growth and developmental benefits to their children by eating more fish than these groups of women typically do.” (See “Feds Advise Kids and Pregnant Women to Eat More Fish
(Canned tuna is one of the best food sources of omega-3s … though the cooked-twice processing that big national brands undergo cuts their tuna's omega-3 content substantially. See our sidebar, “Vital Choice tuna: More omega-3s, less mercury”, below.)
Now, the biggest, longest, best study ever conducted has once again affirmed the safety of almost all ocean fish … including tuna and all other commonly consumed species.
Vital Choice tuna: More omega-3s, less mercury
All Vital Choice albacore comes from a North Pacific fishery in which smaller boats line-catch individual tuna using the sustainable troll method, which ensures careful handling of each fish, safety for dolphins, and very minimal by-catch.
Thanks to its sustainable harvest and lower mercury content, albacore from this fishery is categorized as "Super Green" by Monterey Bay Aquarium.
Vital Choice albacore tuna is sustainably harvested by our neighbor Paul Hill, who quickly flash-freezes it on his small boat to preserve the fish at its peak of freshness.
Because predatory fish such as tuna accumulate mercury over time, Paul provides us with younger, smaller albacore tuna (14 lbs. or less) for optimal purity.
The mercury content of individual fish vary, but the smaller, younger albacore tuna caught by the troll fishery that supplies our tuna average less mercury than the generally much larger, older tuna caught for canning by national brands.
And because we choose only smaller fish from this certified-sustainable troll fishery, testing by independent laboratories confirms that Vital Choice albacore averages substantially less mercury than national brands of "white" (albacore) tuna.
The average mercury content of Vital Choice albacore is 0.25 ppm. In contrast, the FDA-reported average mercury concentration in fresh and canned albacore is 0.35 ppm.
The FDA's average figure for mercury in albacore (0.35 ppm) is higher than ours (0.25 ppm) because the FDA tested standard canned albacore, most of which is older and larger than ours.
In addition to being the purest fish, our smaller albacore also have higher average levels of omega-3s.
This is because the albacore processed by national brands is cooked twice (before it's cleaned and again in the can), while ours is cooked once, in the can.
Seychelles study finds zero harm from fish-heavy maternal diets
The Seychelles Child Development Study (SCDS) remains the longest and largest population study of its kind.
It began in the mid-1980s, as a partnership between the University of Rochester, Ulster University, and the Republic of Seychelles … a cluster of islands in the Indian Ocean.
The nation's 89,000 residents eat far more fish than Americans or Europeans do … which makes the Seychelles a perfect place to examine the effects of daily exposure to fish-borne mercury, from conception through adolescence.
For the most recent analysis, study scientists followed more than 1,500 mothers – who ate more than 8 fish-centered meals per week – and their children (Strain JJ et al. 2015).
At 20 months after birth, the children underwent a battery of tests designed to measure their communication skills, behavior, and motor skills.
The researchers also collected hair samples from the mothers at the time of their pregnancy to measure the levels of prenatal mercury exposure.
And the amount of mercury to which children were exposed before birth did not correlate with lower test scores … a finding that echoed the results of all previous analyses within the Seychelles Study.
(Other parts of the Seychelles Study have followed children from birth on into their 20s – with no link found between high fish consumption and any harm to brain or overall development.)
The researchers also measured the omega-3 fatty acid levels in the pregnant women and found that the children of mothers with higher omega-3 levels performed better on certain brain tests.
As co-author Edwin van Wijngaarden, Ph.D., said, “These findings show no overall association between prenatal exposure to mercury through fish consumption and neurodevelopmental outcomes.” (UR 2015)
Maternal diets high in omega-6 produced some harm
The anti-inflammatory effects of fish-source omega-3s led the lead authors to speculate that they may block the negative effects of mercury.
That idea was supported – indirectly – by the fact that the children of Seychelles mothers with relatively high blood levels of omega-6 fatty acids performed worse than their peers on tests that measured children's motor skills.
According to lead author Sean Strain, Ph.D., of the Ulster University, “The findings indicate that the type of fatty acids a mother consumes before and during pregnancy may make a difference in terms of their child's future neurological development.” (UR 2015)
Why would that be so? In excess, omega-6 fatty acids fuel inflammation and disease … and intake of omega-6 fatty acids rose sharply over the past 40 years, worldwide.
This historically unprecedented omega-6 overload stemmed from newly copious consumption of cheap vegetables oils – soy, corn, safflower, sunflower, cottonseed – and foods made with them.
A large and growing body of evidence shows that a now-common “omega balance” in people's diets – far too many omega-6s versus omega-3s – drives heart disease, cancer, dementia, inflammation, auto-immune diseases, and more. (See our Know Your Omega-3/6 Numbers page
and the Omega-3/Omega-6 Balance
section of our website.)
As principal investigator Philip Davidson, Ph.D., of the University of Rochester said: “These findings indicate that there may be an optimal balance between the different inflammatory properties of fatty acids that promote fetal development and that these mechanisms warrant further study.” (UR 2015)
Omega-3s may protect against mercury … but selenium likely matters more
Frankly, we doubt the study authors' hypothesis that the omega-3s in fish protect against their mercury.
Omega-3s may reduce mercury-related harm, but another nutrient in fish is more likely to explain the utter lack of harm from the fish-heavy diet of the Seychelles … and other nations, like Japan.
Mercury inflicts harm to brains by binding to selenium – a key part of the body's own antioxidant network – thereby allowing oxidation of brain cells (neurons) and also fueling inflammation.
As in the Seychelles, Japanese people consume far more fish than Americans do, but show no signs of harm from mercury … probably because almost all ocean fish contain much more selenium than mercury.
The mercury-selenium interaction explains why only two classes of fish are proven to pose a mercury-poisoning risk:
Fresh-water fish low in selenium that live in rivers or lakes downwind from coal-fired power plants (coal emissions contains mercury).
The few, uncommonly consumed ocean species that contain significantly more mercury than selenium: marine mammals (whales, seals) and a few ocean fish (such as shark and swordfish).
This fact may explain why three decades of research in the Seychelles have consistently shown that copious consumption of ocean fish by pregnant mothers – an average of 12 meals per week, nationwide – has not harmed their children.
Davidson PW, Cory-Slechta DA, Thurston SW, Huang LS, Shamlaye CF, Gunzler D, Watson G, van Wijngaarden E, Zareba G, Klein JD, Clarkson TW, Strain JJ, Myers GJ. Fish consumption and prenatal methylmercury exposure: cognitive and behavioral outcomes in the main cohort at 17 years from the Seychelles child development study. Neurotoxicology. 2011 Dec;32(6):711-7. doi: 10.1016/j.neuro.2011.08.003. Epub 2011 Aug 25.
Davidson PW, Leste A, Benstrong E, Burns CM, Valentin J, Sloane-Reeves J, Huang LS, Miller WA, Gunzler D, van Wijngaarden E, Watson GE, Zareba G, Shamlaye CF, Myers GJ. Fish consumption, mercury exposure, and their associations with scholastic achievement in the Seychelles Child Development Study. Neurotoxicology. 2010 Sep;31(5):439-47. doi: 10.1016/j.neuro.2010.05.010. Epub 2010 May 31.
Myers GJ, Thurston SW, Pearson AT, Davidson PW, Cox C, Shamlaye CF, Cernichiari E, Clarkson TW. Postnatal exposure to methyl mercury from fish consumption: a review and new data from the Seychelles Child Development Study. Neurotoxicology. 2009 May;30(3):338-49. doi: 10.1016/j.neuro.2009.01.005. Epub 2009 Jan 21. Review.
Orlando MS, Dziorny AC, Harrington D, Love T, Shamlaye CF, Watson GE, van Wijngaarden E, Davidson PW, Myers GJ. Associations between prenatal and recent postnatal methylmercury exposure and auditory function at age 19 years in the Seychelles Child Development Study. Neurotoxicol Teratol. 2014 Nov-Dec;46:68-76.
Strain JJ et al. 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. Am J Clin Nutr March 2015 ajcn.100503; First published online January 21, 2015. doi:10.3945/ajcn.114.100503
University of Rochester (UR). Fatty Acids in Fish May Shield Brain from Mercury Damage. January 21, 2015. http://www.urmc.rochester.edu/news/story/index.cfm?id=4238
van Wijngaarden E, Thurston SW, Myers GJ, Strain JJ, Weiss B, Zarcone T, Watson GE, Zareba G, McSorley EM, Mulhern MS, Yeates AJ, Henderson J, Gedeon J, Shamlaye CF, Davidson PW. Prenatal methyl mercury exposure in relation to neurodevelopment and behavior at 19 years of age in the Seychelles Child Development Study. Neurotoxicol Teratol. 2013 Sep-Oct;39:19-25. doi: 10.1016/j.ntt.2013.06.003. Epub 2013 Jun 14.
Watson GE, van Wijngaarden E, Love TM, McSorley EM, Bonham MP, Mulhern MS, Yeates AJ, Davidson PW, Shamlaye CF, Strain JJ, Thurston SW, Harrington D, Zareba G, Wallace JM, Myers GJ. Neurodevelopmental outcomes at 5 years in children exposed prenatally to maternal dental amalgam: the Seychelles Child Development Nutrition Study. Neurotoxicol Teratol. 2013 Sep-Oct;39:57-62. doi: 10.1016/j.ntt.2013.07.003. Epub 2013 Jul 13.