Tag Archives: omega-6

Seafood Mercury Concerns Subside Amid New Research | The Paleo Diet

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-3 from 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.

Christopher James Clark, B.B.A.

@nutrigrail
Nutritional Grail
www.ChristopherJamesClark.com

Christopher James Clark | The Paleo Diet TeamChristopher James Clark, B.B.A. is an award-winning writer, consultant, and chef with specialized knowledge in nutritional science and healing cuisine. He has a Business Administration degree from the University of Michigan and formerly worked as a revenue management analyst for a Fortune 100 company. For the past decade-plus, he has been designing menus, recipes, and food concepts for restaurants and spas, coaching private clients, teaching cooking workshops worldwide, and managing the kitchen for a renowned Greek yoga resort. Clark is the author of the critically acclaimed, award-winning book, Nutritional Grail.

REFERENCES

[1] Bradbury, J. (May 2011). Docosahexaenoic Acid (DHA): An Ancient Nutrient for the Modern Human Brain. Nutrients, 3(5). Retrieved from http://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 http://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 http://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 http://www.ncbi.nlm.nih.gov/pubmed/20561558

[6] Ibid, Ralston.

Selecting Seafood for Health and Sustainability | The Paleo Diet

There’s no question that seafood is a great source of protein and omega-3 fatty acids, and that it should form an integral part of the Paleo Diet. But seafood doesn’t thrive in polluted waters, overfished waters, or in habitats damaged by fishing gear. So to get the good without the bad—and to ensure we have it for years to come—we need to know which species have the holy trinity of seafood: sustainable, safe, and nutritious.

Sustainable

Sustainably caught fish may seem like a nice-to-have, but it should really be on par with nutrition for importance when selecting seafood. Not only do we want our food to be harvested or caught in its highest nutritive state, we want that to continue indefinitely. It hasn’t always been that way, but more and more fisheries are making sustainability a reality by considering the health of ecosystems and fish populations as well as their profits. Seafood Watch® makes science-based recommendationsfor sustainable seafood.1,2,3 Here’s their current list of best choices, good alternatives, and choices to avoid.

Selecting Seafood for Health and Sustainability

The seafood recommendations in this guide are credited to the Monterey Bay Aquarium Foundation ©2014. All rights reserved.

Download the PDF

Safe

In the seafood world, mercury, dioxins, and PCBs are the usual suspects when it comes to contamination. They’re not normally features of a “healthy and abundant stock” which is a fundamental criterion for sustainability1—so if you’re choosing sustainable, you’re likely choosing safe too. In addition, SeafoodWatch® posts health alerts if there are specific concerns for human health from a fishery.

Mercury, however, is a changing story. Mercury accumulates in fat tissues of large, long-lived predatory fish or shellfish, ultimately ending up on our dinner plates. We’ve been cautioned to limit these species in our diets, but surprisingly, that’s not the whole story. Mercury readily and irreversibly binds to selenium,4 which means that as long as the fish you’re eating has more selenium than mercury, your body won’t actually be retaining the mercury you ingest. And since the oceans are full of selenium, most ocean fish are perfectly safe to eat.5,6 Simply avoid shark and limit swordfish, tilefish, and king mackerel or use this infographic to moderate your consumption . Also keep in mind that in freshwater, mercury and selenium levels vary greatly with the composition of the surrounding soil. Check with your local authorities for health alerts.

Nutritious

Fish are great sources of vitamins and minerals as well as protein, but the biggest benefit from eating fish is the omega-3 fatty acids EPA and DHA.7 Anyone who’s had king salmon and a haddock fillet can tell you, however, that all fish are not created equal when it comes to fat—and they’re not all created equal when it comes to omega-3 to omega-6 ratios either—and that matters! Here’s some nutritional data from the USDA for some popular fish and shellfish.6

Sustainable Choices in SeafoodSustainable Choices in Seafood

Highlighted numbers in the first four columns are amounts greater than 1 g/100 g; highlighted numbers in the last column are the fish with ratios greater than 5. A few things jump out.

  • Total fat isn’t everything: the number of fish hitting 1 g/100 g decreases as we move from total fat to polyunsaturated fat to omega-3s.
  • Atlantic mackerel, chinook salmon, herring, swordfish, and Bluefin tuna have high total fat and great omega-3/omega-6 ratios.
  • Only farmed Atlantic salmon has more than 1 g/100 g of omega-6s.
  • All but tilapia have an omega-3/omega-6 ratio greater than 1.
  • There doesn’t seem to be a relationship between total fat and the omega-3/omega-6 ratio. There are high fat options with low ratios (Atlantic salmon) and high ratio options with lower fat (squid).

Sustainable + Safe + Nutritious

So can we have our fish and eat it too? Yes! There is an impressively wide array of sustainable options to choose from, and we can assume that they’re safe choices, not only because they’re sustainable, but because they’re high in selenium. Many of those sustainable options are also fatty fish with great omega-3/omega-6 ratios (anything above 1 is great). SeafoodWatch® compiled their “Super Green List” based on these criteria, but let’s look at the poor performers to compare.

  • Atlantic salmon: not sustainably caught, high omega-6s, ratio close to 1
  • Bluefin tuna: great fat profile, great ratio, but not sustainable
  • Tilapia: sustainably farmed, but lower in fat, ratio less than 1
  • Sharks: more mercury than selenium, not sustainably caught

The bottom line: while some seafood looks good in the nutritional breakdown, from a sustainability standpoint, some species may be better than others. So, eat your recommended portion of omega-3s, but choose options that tick all the boxes for your health as well as the ocean’s.

Andrea MooreAndrea Moore has dipped her toes in a lot of ponds, lakes, and oceans over the years. She has adventured around the world doing odd jobs and studying biology, languages, and sailing.

Now surprisingly settled in Halifax, Nova Scotia, Andrea’s still up to a bit of everything as a marine biologist, a writer, and an editor, living the Paleo lifestyle.

fix-logoFix.com is a lifestyle blog devoted to bringing you expert content to make your life easier. From products, to food, to fishing, to projects, we’ll be providing you with a daily fix of content from our experienced and knowledgeable team of writers.

 

REFERENCES

1. Monterey Bay Aquarium. Developing Seafood Watch® Recommendations. Version: January 23, 2014.

2. Monterey Bay Aquarium. Seafood Watch® Criteria for Aquaculture. Accessed: September 5, 2014.

3. Monterey Bay Aquarium. Seafood Watch ® Criteria for Fisheries. Version: March 31, 2014.

4. Ralston NVC, Ralston CR, Blackwell 3rd JL, Raymond LJ. Dietary and tissue selenium in relation to methylmercury toxicity. NeuroToxicology 2008;29(5):802-11.

5. U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2010. 7th Edition, Washington, DC: U.S. Government Printing Office, December 2010.

6. US Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory. USDA National Nutrient Database for Standard Reference, Release 27. Version Current: August 2014.

7. Kidd PM. Omega-3 DHA and EPA for cognition, behavior, and mood: clinical findings and structural-functional synergies with cell membrane phospholipids. Altern Med Rev 2007;12(3):207-27.

Omega-3 vs. Omega-6: Rethinking the Hypothesis

When you’re eating a meal, you’re probably not thinking about macronutrients, like carbohydrates, fats and proteins. The vast majority of individuals following a Western diet aren’t consciously thinking is this food essential to the human body? It is important to note, however, that while there is no such thing as an “essential carbohydrate,”1 there are “essential fats.”2 Essential in the sense that the human body cannot make these fats endogenously,3 and therefore, must be obtained via diet or supplementation.4 Within the class of essential fats, we have omega-3, which has different forms such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (E’PA).5 However, omega-3 is more commonly known to the general populace as “fish oil.”

Omega 3 fatty acids are long chain in structure and found in a variety of foods.6 The action of these long chain fatty acids is commonly called “anti-inflammatory,” though this is a misnomer.7 They are simply less inflammatory than omega-6 fatty acids. Omega-3 FAs and omega-6 FAs compete for the same enzyme to eventually be converted into anti-inflammatory prostaglandins (PGE3) and less inflammatory leukotrienes and into pro-inflammatory prostaglandins (PGE2) and more inflammatory leukotrienes, respectively.8 This paper then goes on to declare, it is the ratio of omega-6 to omega-3 that is vital to reduce or promote the overall inflammatory state of the body.9,10,11 When we look to the habits of hunter-gatherers, the ratio of omega-6 to omega-3 has been estimated at 2:1 or 3:1.12 This is in contrast to the modern diet, which has been estimated at 10:1, or even 25:1.13

With this evidence, it is assumed that emulating the ratio of hunter-gatherers is correct, if we want to improve bio-markers of health.14 Certainly the theory that an inflammatory diet, full of omega-6 rich vegetable oils and very little omega-3 would likely lead to health problems, makes basic sense.15 However, newer research suggests both omega-6 and omega-3 FAs reduce the risk of heart disease, and the ratio of these fatty acids is “not useful and can be misleading.”16 One study reported that omega-6 FAs do not inhibit the beneficial effects of omega-3 FAs, and the combination of both fatty acids leads to the greatest reduction in levels of inflammation.17

However, the real issue here is that omega-3 FAs bind to G coupled-protein receptors, and cause broad anti-inflammatory effects.18 If you remove the omega-3 FAs from your diet, inflammation returns. This means that adequate omega-3 intake alone, regardless of omega-6 intake, is enough to stop inflammation in the body. The same is apparent when you look at the biochemical pathway of omega-6 and omega-3 FAs. They compete for the same enzyme19 through a process known as competitive inhibition.20

The best method of action to pursue, is to simply follow a Paleo Diet and eat plenty of fish rich in omega-3. If you want to avoid dietary intake of omega-3, and obtain the requirements solely from a supplement, DHA is preferable to all other forms of omega-3, since it can be retro converted into EPA.21 Only in the context of a very inflammatory diet (like the standard Western diet) does the ratio of omega-3 to 6 matter. Another case where the ratio would be of utmost importance, is if you aren’t getting any omega-3 FAs at all. This isn’t to say that the omega-3 to omega-6 ratio is completely irrelevant, but if you’re consuming a Paleo Diet, you will likely be getting the right amounts of these essential fatty acids for optimal health.

References

1. Westman EC. Is dietary carbohydrate essential for human nutrition?. Am J Clin Nutr. 2002;75(5):951-3.

2. Insel, Paul. Nutrition: Custom Edition. 4th Edition. Jones & Bartlett Learning, 2010; 182.

3. Chang CY, Ke DS, Chen JY. Essential fatty acids and human brain. Acta Neurol Taiwan. 2009;18(4):231-41.

4. Singh M. Essential fatty acids, DHA and human brain. Indian J Pediatr. 2005;72(3):239-42.

5. Wainwright PE. Dietary essential fatty acids and brain function: a developmental perspective on mechanisms. Proc Nutr Soc. 2002;61(1):61-9.

6. Meyer BJ, Mann NJ, Lewis JL, Milligan GC, Sinclair AJ, Howe PR. Dietary intakes and food sources of omega-6 and omega-3 polyunsaturated fatty acids. Lipids. 2003;38(4):391-8.

7. Foitzik T, Eibl G, Schneider P, Wenger FA, Jacobi CA, Buhr HJ. Omega-3 fatty acid supplementation increases anti-inflammatory cytokines and attenuates systemic disease sequelae in experimental pancreatitis. JPEN J Parenter Enteral Nutr. 2002;26(6):351-6.

8. Macsai MS. The role of omega-3 dietary supplementation in blepharitis and meibomian gland dysfunction (an AOS thesis). Trans Am Ophthalmol Soc. 2008;106:336-56.

9. Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002;56(8):365-79.

10. Gómez candela C, Bermejo lópez LM, Loria kohen V. Importance of a balanced omega 6/omega 3 ratio for the maintenance of health: nutritional recommendations. Nutr Hosp. 2011;26(2):323-9.

11. Simopoulos AP. The omega-6/omega-3 fatty acid ratio, genetic variation, and cardiovascular disease. Asia Pac J Clin Nutr. 2008;17 Suppl 1:131-4.

12. Cordain L, Eaton SB, Sebastian A, et al. Origins and evolution of the Western diet: health implications for the 21st century. Am J Clin Nutr. 2005;81(2):341-54.

13. Yan L, Bai XL, Fang ZF, Che LQ, Xu SY, Wu D. Effect of different dietary omega-3/omega-6 fatty acid ratios on reproduction in male rats. Lipids Health Dis. 2013;12:33.

14. Apte SA, Cavazos DA, Whelan KA, Degraffenried LA. A low dietary ratio of omega-6 to omega-3 Fatty acids may delay progression of prostate cancer. Nutr Cancer. 2013;65(4):556-62.

15. Kang JX, Liu A. The role of the tissue omega-6/omega-3 fatty acid ratio in regulating tumor angiogenesis. Cancer Metastasis Rev. 2013;32(1-2):201-10.

16. Anton SD, Heekin K, Simkins C, Acosta A. Differential effects of adulterated versus unadulterated forms of linoleic acid on cardiovascular health. J Integr Med. 2013;11(1):2-10.

17. Pischon T, Hankinson SE, Hotamisligil GS, Rifai N, Willett WC, Rimm EB. Habitual dietary intake of n-3 and n-6 fatty acids in relation to inflammatory markers among US men and women. Circulation. 2003; 108(2): 155-160.

18. Oh DY, Talukdar S, Bae EJ, et al. GPR120 is an omega-3 fatty acid receptor mediating potent anti-inflammatory and insulin-sensitizing effects. Cell. 2010;142(5):687-98.

19. Babcock TA, Novak T, Ong E, Jho DH, Helton WS, Espat NJ. Modulation of lipopolysaccharide-stimulated macrophage tumor necrosis factor-alpha production by omega-3 fatty acid is associated with differential cyclooxygenase-2 protein expression and is independent of interleukin-10. J Surg Res. 2002;107(1):135-9.

20. Oleñik A, Mahillo-fernández I, Alejandre-alba N, et al. Benefits of omega-3 fatty acid dietary supplementation on health-related quality of life in patients with meibomian gland dysfunction. Clin Ophthalmol. 2014;8:831-6.

21. Conquer JA, Holub BJ. Dietary docosahexaenoic acid as a source of eicosapentaenoic acid in vegetarians and omnivores. Lipids. 1997;32(3):341-5.

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