Seafood and Human Health

Though estimates of human longevity before the Industrial Revolution should be viewed with caution,[1] it appears that the Knights Templar, a religious military order holding sway for nearly two centuries during the Middle Ages, lived exceptionally longer lives than their contemporaries.[2] While generally attributed to divine providence, a more recent conjecture has suggested that strict adherence to the order’s lifestyle precepts, particularly around diet, was the key factor. And an exemplary diet it was: meat limited to three days weekly; low-to-moderate amounts of wine during meals; and fruits, vegetables, pulses, cheese, olive oil … and seafood … all in copious amounts. The intrepid Templars even tried their hand at aquaculture.[3]

The legendary Ancel Keys and Seven Countries

The possible benefits of the Mediterranean-type diet enjoyed by the knights would not come under scrutiny until much later, largely beginning with the ground-breaking work of Ancel Keys, an American physiologist. Two puzzles intrigued Keys shortly after World War II: the decrease in coronary artery disease in Europe and the epidemic of myocardial infarctions among American executives.[4]

Suspecting food was a factor in both cases he embarked on a series of pioneering epidemiological studies which looked at dietary habits and cardiovascular disease (CVD), eventually culminating in a major research project – the so-called Seven Countries Study – the results of which were published in 1970. The conclusion was clear: dietary levels of saturated fats correlate with blood cholesterol and heart attacks, all of which were lower in Japan and the Mediterranean region.[5]

The “Eskimo diet”

At around the same time as Keys and colleagues were finalizing their landmark study, anecdotal reports of a low incidence of coronary heart disease in the Inuit of Greenland were surfacing. Danish physicians, upon investigating, speculated that the “Eskimo diet” of large quantities of high-fat whale and seal meat – and specifically their content of omega-3 polyunsaturated fatty acids (PUFAs) – was responsible.[6] [7] [8]

It turned out, however, that the real reason behind the reportedly lower rates of heart disease were gaps in Greenland’s health statistics, a result of the considerable logistical difficulties associated with monitoring a region of many isolated and far-flung communities.[9] Indeed, as subsequent studies showed, the prevalence of CVD in Inuit – whether from Greenland, Canada or Alaska – paralleled that of their non-Inuit counterparts.[10] [11] [12]

Fish oils and human health

Nonetheless, the Eskimo diet studies launched extensive investigations into marine-sourced omega-3 PUFAs (the other nutritional components of seafood were largely ignored), and facilitated the development of a billion dollar nutraceutical industry around fish oil as a dietary supplement.[13] [14] Two of those omega-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are found in seafood, the only major source for humans; and research in the intervening years has provided compelling evidence that EPA and DHA – particularly when consumed via seafood – can provide critical health benefits.[15] [16]

But curiously, and for reasons that are currently unclear, there is limited scientific support for health benefits of omega-3s derived from marine oil supplementation[17] [18] [19] [20] [21] [22] — for which it is typically marketed – nor any clear evidence for an effect during pregnancy on the outcome of children’s neurodevelopment and growth.[23] [24] [25] [26] [27] Likewise, systematic reviews show little evidence, for example, that supplementation during pregnancy and/or lactation reduces childhood allergies[28] or favorably affects child adiposity,[29] or that supplemented formula provides clear longterm benefits to preterm infants.

The benefits of seafood

In contrast with fish oil supplementation, however, scientific support for the benefits of seafood consumption is substantial. Large cohort studies, systematic reviews and/or meta-analyses have shown, for example, that:

  • about 1-2 servings per week during pregnancy compared to no seafood intake correlates with enhanced neurodevelopment in children;[31] [32]
  • low or moderate fish consumption (1–4 servings/week) decreases the risk of mortality from coronary heart disease;[33] [34] [35] [36] [37]
  • increasing fish consumption is associated with increasing prevention of acute coronary syndrome;[38]
  • omega-3 PUFA intake via fish consumption is associated with a lower risk of breast cancer;[39]
  • consumption of 60 grams (2 ounces) of fish per day compared to no seafood intake is associated with a reduction in all-cause mortality.[40]

Though there is a wide variation in the nutritional characteristics between and among fish and shellfish species, seafood contains calories and proteins with high biological value along with essential nutrients (e.g., vitamins A, D, E and B12, zinc, selenium, iodine, taurine, and the aforementioned omega-3 PUFAs), many with well-established health benefits and necessary for optimum fetal development in pregnancy.[41] [42] [43] [44] [45] [46] For some segments of the population, seafood is also an important source of vitamin D and iodine.[47] [48]

Seafood and diet

The work of Ancel Keys, who went on to become a huge proponent of Mediterranean-type diets, laid much of the groundwork that has ultimately led to widespread expert agreement that diet – as the Knights Templar seem to have suspected – is important in promoting health and preventing disease and, further, that seafood is an integral component of a dietary regime associated with good health.[49] [50] In this regard, it may not be an accident that Japan, one of the world’s top consumers of seafood, has the highest reported life expectancy globally along with one of the lowest mortality rates from heart-related diseases.[51]

The scientific consensus around seafood benefits has led many governments via food-based dietary guidelines to recommend at least two servings of fish per week for older children, adolescents and adults to ensure the provision of key nutrients. Still, restrictions on consumption of a few select species due to contaminants, such as mercury, are still required, especially by sensitive populations. For most, however, and as shown by numerous studies, the benefits far outweigh the risks.[52]

The value of seafood, ultimately, has perhaps been most eloquently expressed by fisheries and aquaculture researchers, Albert Tacon and Marc Metian, in a recent publication:[53]

In a world where nearly 30% of humanity is suffering from malnutrition and over 70% of the  planet is covered with water, aquatic foods represent an essential component of the global food basket to improve the nutrition, health, and well being of all peoples.


[1]   Wilmoth, J.R. 2000. Demography of longevity: past, present, and future trends. Experimental Gerontology 35(9-10): 1111-1129.

[2]   Franceschi, F. et al. 2014. The diet of Templar Knights: Their secret to longevity? Digestive and Liver Disease 46(7): 577-578.

[3]   ibid.

[4]   Andrade, J. et al. 2009. Ancel Keys and the lipid hypothesis: From early breakthroughs to current management of dyslipidemia. BC Medical Journal 51(2): 66-72.

[5]   Keys, A. (Ed.). 1970. Coronary heart disease in seven countries. Circulation 41(4 Suppl.): 1-198.

[6]   Bang, H.O., Dyerberg, J. and Nielsen, A.B. 1971. Plasma lipid and lipoprotein pattern in Greenlandic west-coast Eskimos. The Lancet 297(7710): 1143-1146.

[7]   Bang, H,O. Dyerberg, J. and Hjorne N. 1976. The composition of food consumed by Greenland Eskimos. Acta Medica Scandinavica 200(1-6): 69-73.

[8]   Dyerberg, J. et al. 1978. Eicosapentanoic acid and prevention of thrombosis and atherosclerosis. The Lancet 312(8081): 117-119.

[9]   Fodor, J.G. et al. 2014. “Fishing” for the origins of the “Eskimos and heart disease” story: facts or wishful thinking? Canadian Journal of Cardiology 30(8): 864-868.

[10] Bjerregaard, P. and Dyerberg, J. 1988. Mortality from ischaemic heart disease and cerebrovascular disease in Greenland. International Journal of Epidemiology 17(3): 514-519.

[11] Pedersen, H.S. et al. 1999. N-3 fatty acids as a risk factor for haemorrhagic stroke. The Lancet 353(9155): 812-813.

[12] Bjerregaard, P., Young, T.K. and Hegele, R.A. 2003. Low incidence of cardiovascular disease among the Inuit – what is the evidence? Atherosclerosis 166(2): 351-357.

[13] Fodor et al., op cit.

[14] Albert, B.B. et al. 2016. Marine oils: complex, confusing, confounded? Journal of Nutrition &  Intermediary Metabolism 5: 3-10.

[15] McManus, A. et al. 2011. Omega-3 fatty acids. What consumers need to know. Appetite 57: 80-83.

[16] Riediger, N.D. et al. 2009. A systemic review of the roles of n-3 fatty acids in health and disease. Journal of the American Dietetic Association 109(4): 668-679.

[17] Rizos, E.C. et al. 2012. Association between omega-3 fatty acid supplementation and risk of major cardiovascular disease events – A systematic review and meta-analysis. JAMA 308(10): 1024-1033.

[18] Umar, A. et al. 2015. Colorectal cancer prevention and fishful thinking. Journal of the National Cancer Institute 107(4): art. djv052.

[19] Persson, P.B. and Zakrisson, A. 2015. Dietary supplements: health from the ocean? Acta Physiologica 215(3): 119-122.

[20] Weylandt, K.H. et al. 2015. Omega-3 polyunsaturated fatty acids: The way forward in times of mixed evidence. BioMed Research International 2015: art. 143109.

[21] Hanne, M.K.; et al. 2015. ω-3 fatty acids and cardiovascular diseases: effects, mechanisms and dietary relevance. International Journal of Molecular Sciences 16(9): 22636-22661.

[22] Albert et al., op cit.

[23] Leung, B, Wiens, K. and Kaplan, B. 2011. Does prenatal micronutrient supplementation improve children’s mental development? A systematic review. BMC Pregnancy and Childbirth 11: art. 12.

[24] Lo, A. et al. 2012. The effects of maternal supplementation of polyunsaturated fatty acids on visual, neurobehavioural, and developmental outcomes of the child: a systematic review of the randomized trials. Obstetrics and Gynecology International 2012: art. 591531.

[25] Campoy, C. et al. 2012. Omega 3 fatty acids on child growth, visual acuity and neurodevelopment. British Journal of Nutrition 107(Suppl 2): 85-106.

[26] Gould, J.F., Smithers, L.G. and Makrides, M. 2013. The effect of maternal omega-3 (n-3) LCPUFA supplementation during pregnancy on early childhood cognitive and visual development: a systematic review and meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition 97(3): 531-544.

[27] Delgado-Noguera, M.F. et al. 2015. Supplementation with long chain polyunsaturated fatty acids (LCPUFA) to breastfeeding mothers for improving child growth and development. Cochrane Database of Systematic Reviews 7: art. CD007901.

[28] Gunaratne, A.W. et al. 2015. Maternal prenatal and/or postnatal n-3 long chain polyunsaturated fatty acids (LCPUFA) supplementation for preventing allergies in early childhood. Cochrane Database of Systematic Reviews 7: art. CD010085.

[29] Stratakis, N. et al. 2014. Effect of maternal n‐3 long‐chain polyunsaturated fatty acid supplementation during pregnancy and/or lactation on adiposity in childhood: a systematic review and meta‐analysis of randomized controlled trials. European Journal of Clinical Nutrition 68(12): 1277‐1287.

[30] Schulzke, S.M. et al. 2011. Longchain polyunsaturated fatty acid supplementation in preterm infants. Cochrane Database of Systematic Reviews 2: art. CD000375

[31] Hibbeln, J.R. et al. 2007. Maternal seafood consumption in pregnancy and neurodevelopmental outcomes in childhood (ALSPAC study): an observational cohort study. The Lancet 369(9561): 578-585.

[32] Oken, E. et al. 2008. Associations of maternal fish intake during pregnancy and breastfeeding duration with attainment of developmental milestones in early childhood: a study from the Danish National Birth Cohort. American Journal of Clinical Nutrition 88(3): 789-796.

[33] He, K. et al. 2004. Accumulated evidence on fish consumption and coronary heart disease mortality: a meta-analysis of cohort studies. Circulation 109(22): 2705-2711.

[34] Whelton. S.P. et al. 2004. Meta-analysis of observational studies on fish intake and coronary heart disease. American Journal of Cardiology 93, 1119-1123.

[35] Harris, W.S. Kris-Etherton, P.M. and Harris, K.A. 2008. Intakes of long-chain omega-3 fatty acid associated with reduced risk for death from coronary heart disease in healthy adults. Current Atherosclerosis Reports 10(6): 503-509.

[36] Mozaffarian, D. and Rimm, E.B., 2006. Fish intake, contaminants, and human health: evaluating the risks and the benefits. JAMA 296(15): 1885-1899.

[37] Zheng, J. et al. 2012. Fish consumption and CHD mortality: an updated meta-analysis of seventeen cohort studies. Public Health Nutrition 15(4): 725-737.

[38] Leung Yinko, S.S.L. et al. 2014. Fish consumption and acute coronary syndrome: a meta-analysis. American Journal of Medicine 127(9): 848-857.

[39] Zheng, J.-S. et al. 2013. Intake of fish and marine n-3 polyunsaturated fatty acids and risk of breast cancer: meta-analysis of data from 21 independent prospective cohort studies. British Medical Journal

346: art. f3706.

[40] Zhao, L.G. et al. 2016. Fish consumption and all-cause mortality: a meta-analysis of cohort studies. European Journal of Clinical Nutrition 70(2): 155-161.

[41] Vogiatzoglou, A. et al. 2009. Dietary sources of vitamin B-12 and their association with plasma vitamin B-12 concentrations in the general population: the Hordaland Homocysteine Study. American Journal of Clinical Nutirtion 89(4): 1078-1087.

[42] Flores-Mateo, G. et al. 2006. Selenium and coronary heart disease: a meta-analysis. American Journal of Clinical Nutrition 84(4): 762-773.

[43] Wójcik, O.P. et al. 2010. The potential protective effects of taurine on coronary heart disease. Atherosclerosis 208(1): 19-25.

[44] Larsen, R. et al. 2011. Health benefits of marine foods and ingredients. Biotechnology Advances 29: 508-518.

[45] Hamed, I. et al. 2015. Marine bioactive compounds and their health benefits: A review. Comprehensive Reviews in Food Science and Food Safety 14(4): 446-465.

[46] Starling, P. et al. 2015. Fish intake during pregnancy and foetal neurodevelopment—a systematic review of the evidence. Nutrients 7(3): 2001-2014.

[47] Zimmermann, M.B. 2011. The role of iodine in human growth and development. Seminars in Cell & Developmental Biology 22(6): 645-652.

[48] Lehmann, U. et al. 2015. Efficacy of fish intake on vitamin D status: a meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition 102(4): 837-847.

[49] Katz, D.L. and Meller, S. 2014. Can we say what diet is best for health? Annual Review of Public Health 35(1): 83-103.

[50] Trichopoulou, A. et al. 2014. Definitions and potential health benefits of the Mediterranean diet: views from experts around the world. BMC Medicine 12: art. 112.

[51] Yamori, Y. 2009. Do diets good for longevity really exist? Lessons from the eating habits of countries with long-lived populations. Japanese Medical Association Journal 52(1): 17-22

[52] Gil, A. and Gil, F. 2015. Fish, a Mediterranean source of n-3 PUFA: benefits do not justify limiting consumption. British Journal of Nutrition 113(S2): S58-S67.

[53] Tacon, A.G.J. and Metian, M. 2013. Fish matters: importance of aquatic foods in human nutrition and global food supply. Reviews in Fisheries Science 21(1): 22-38.

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