There are two series of essental fatty acids which are necessary for both animal and human life. They are built up only by plants and cannot be synthesized by animals or humans. Therefore, they must be supplied in the diet. The n-6 series originate in the linoleic acid (LA, 18:2n-6), and the n-3 series in the α-linolenic acid (ALA, 18:3n-3). Physiologically more important than these parental fatty acids are their elongated and desaturated derivatives or metabolits. These fatty acids affect the fluidity, flexibility and permeability of the membranes, are precursors of the eicosanoids and necessary for maintaining the impermeability barrier of the skin.^1,2

Since the 1970s knowledge concerning the significance ot the long-chain polyunsaturated fatty acids (PUFAs) of the n-3 type, especially eicosapentaenoc acid (EPA) and docosahexaenoic acid (DHA), for human health has increased considerably.³ Excellent source of these fatty acids are fish oils.⁴ High levels of n-3 fatty acids are present not only in lipid rich marine fish like herring (Clupea harengus) or mackerel (Scomber scombrus) but also in several freshater fish species. Well known for their high content of n-3 PUFAs are e.g. silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis), which are reared mainly in Asia.⁵

The fatty acid composition of fish is based on that of their food, and the typical high levels of PUFAs in fish lipids result of the fatty acid composition of the phytoplankton.^6,7 Since fatty acid content of fish reflects, to a large extent, that of their feed, in aquaculture it is possible to influence the fatty acid levels of cultured fish by suitable composition ot the diets.^8,9

Today in modern diets for fish culture the necessary n-3 PUFAs are supplied mainly by adding fish oil. In future oils of yeast, microalgae and genetically modified oilseed plants will be used to a great extent in fish feed.^10,11 In evaluating the value of fish as wholesome human diet it is necessary to consider not only the percentage of n-3 PUFAs in the lipid but also the lipid level in the muscle.¹² That means, lipid rich fish generally are more suitable for sound nutrition than lean fish.

Many authors have demonstrated that n-3 PUFAs have antiatherosclerotic efficacy and can reduce disease of the circulating system.^13,14 Recommended consumption levels of EPA and DHA for humans lie within the range of 300-400mg per day.¹⁵ With two portions of lipid rich fish per week it is possible to satisfy this demand.¹⁶ But there is evidence that long-chain polyunsaturated n-3 fatty acids may have also beneficial effects on diseases other than those of the heart and the blodd vessels. These are inflammatory diseases,¹⁷ arthritis,¹⁸ nephritis,¹⁹ lupus erythematosis,²⁰ multiple sclerosis,²¹ strokes,²² cancer,²³ skin diseases,^24,25 asthma,²⁶ Alzheimer disease,²⁷ and age-related macular degeneration.^28,29

Consumption of fish containing n-3 PUFAs by pregnant women is very important for the development and health of the foetus and the newborn infant.³⁰⁻³⁴ In a study with about 1500 middle-aged and elderly participants it was shown, that high intake of EPA and DHA was positively associated with brain volume, visual memory and abstract thinking, even in persons free of clinical dementia.³⁵

Meanwhile many comprehensive studies were published which clearly demonstrate the general cardioprotective value of fish consumption or the so-called Mediterranean diet (DASH: Dietary approaches to stop hypertension).^{36− 40}

In an extensive paper the effect of dietary pattern and individual foods on mortality and cancer recurrence among cancer survivors was studied.⁴¹ In this investigation more than 200000 cancer survivors were included. It was shown that higher intakes of fish and vegetables were inversely associated with overall mortality. Thus high quality diet with regular intake of fishcan contribute to human health.

None.

Author declares that there is no conflict of interest.

1. Mead JF. The metabolism ofthe polyunsaturated fatty acids. Chem Fats Other Lipids. 1971;9:159−192.
2. Horrobin DF, Manku MS. Clinical biochemistry of essential fatty acids (21−53). In: Horrobin DF, editor. Omega−6 Essential Fatty Acids. Pathophysiology and Roles in Clinical Medicine. USA: Wiley−Liss; 1990.
3. Stansby ME. Nutritional properties of fish oil for human consumption – modern aspects (289−308). In: Stansby ME, editor. Fish Oils in Nutrition. USA: Van Nostrand Reinhold; 1990.
4. Singer P. Fisch gegen Herzinfarkt. Umschau Buchverlag Breidenstein GmbH, Frankfurt am Main. 1997.
5. Steffens W, Wirth M. Cyprinids as a valuable source of essential fatty acids for human health: a review. Asian Fish Sci. 1997;10:83−90.
6. Cowey CB. Some effects of nutrition on flesh quality of cultured fish (227−236). In: Kaushik S, Luquet P, editors. Fish Nutrition in Practice. Biarritz: IVth Intern Symp Fish Nutrition Feeding; 1993:24−27.
7. Steffens W. Effects of variation in essential fatty acids in fish feeds on nutritive value of freshwater fish for humans. Aquaculture. 1997;151:97−119.
8. Mráz J, Zajíc T, Pickova J. Culture of common carp (Cyprinus carpio) with defined flesh quality for prevention of cardiovascular diseases using finishing feeding strategy. Neuroendocrinol Lett. 2012;33:60−67.
9. Steffens W. Aquaculture produces wholesome food: cultured fish as a valuable source of n−3 fatty acids. Aquacult Int. 2016;24:787−802.
10. Bell JG, Tocher DR. Novel ingredients for aquafeeds to improve sustainability and security of supply. Fishfarming Xpert No. 2012:43−46.
11. Steffens W. Mangel an Fischöl wird die künftige Entwicklung der Aquakultur nicht beeinträchtigen. Fischer Teichwirt. 2014;65(1):23−25.
12. Hardy RW. Farmed fish and omega−3 fatty acids. Aquac Mag. 2003;1−3.
13. Singer P, Wirth M, Berger I, et al. Long−chain ω−3 fatty acids are the most effective polyunsaturated fatty acids for dietary prevention and treatment of cardiovascular factors. Conclusions from clinical studies. In: Simopoulos AP, editor. Nutrients in the Control of Metabolic Diseases. Karger, Basel: World Rev Nutr Diet; 1992.
14. Singer P. Was sind, wie wirken Omega−3−Fettsäuren? 44 Fragen – 44 Antworten, 3rd ed. Umschau Zeitschriftenverlag Breidenstein GmbH, Frankfurt am Main. 2000.
15. Singer P, Omega−3−Fettsäuren. Theoretische Aspekte und praktische Hinweise für Prophylaxe und Therapie. Med Welt. 2006;(56):428−432.
16. Crampton VO, Nanton DA, Ruohonen K, et al. Demonstration of salmon farming as a net producer of fish protein and oil. Aquaculture Nutrition. 2010;16:437−446.
17. Higgs GA. The role of eicosanoids in inflammation. Progr Lipid Res.1986;25:555−561.
18. Kremer JM, Lawrence D, Jubiz W. Different doses of fish oil fatty acid supplementation on rheumatoid arthritis. A prospective double−blinded randomized study. Arthritis Rheum.1988;31:530−536.
19. Thais F, Stahl RA. Effect of dietary fish oil on renal function in immune mediated glomerular injury. In: Lands WEM, editors. Proceedings of AOAC short course on polyunsaturated fatty acids and eicosanoids. USA: Champaign, Illinois; 1987.
20. Kelley VE, Ferritti A, Izni S, et al. A fish oil diet rich in eicosapentaenoic acid reduces cyclooxygenase metabolites and suppresses lupus in MLR−lpr mice. J Immunol. 1985;134:1914−1919.
21. Bates D, Cartlidge N, French JM, et al. A double−blind controlled trial of long chain n−3 polyunsaturated fatty acids in the treatment of multiple sclerosis. J Neurol Neurosurg Psychiatr. 1989;52:18−22.
22. Hirai A, Terano T, Saito H, et al. Clinical and epidemiological studies of eicosapentaenoic acid in Japan. In: Lands WEM, editors. Proceedings of AOAC short course on polyunsaturated fatty acids and eicosanoids. USA: Champaign, Illinois; 1987.
23. Karmeli RA. Omega−3 fatty acids and cancer: a review (222−231). In: Lands WEM, editors. Proceedings of AOAC short course on polyunsaturated fatty acids and eicosanoids. USA: Champaign, Illinois; 1987.
24. Rhodes EL. MAXEPA in the treatment of eczema. Brit J Clin Pract. 1984;38(Suppl 31):115−116.
25. Singer P, Ständer M. Fischöl zur adjunktiven Therapie bei Psoriasis. Der Deutsche Dermatologe. 1990;38:1200−1211.
26. Lands WEM, Fish and human health. USA, Orlando: Academic Press; 1986.
27. Gu Y, Nieves JW, Stern Y, et al. Food combination and Alzheimer disease risk: a protective diet. Arch Neurol. 2010;67(6):699−706.
28. Hodge WG, Schachter HM, Barnes D, et al. Efficacy of omega−3 fatty acids in preventing age−related macular degeneration: a systematic review. Ophthalmology. 2006;113(7):1165−1172.
29. Chong EWT, Kreis AJ, Wong TY, et al. Dietary ω−3 fatty acid and fish intake in the primary prevention of age−related macular degeneration. A systematic review and meta−analysis. Arch Ophthalmol. 2008;126(6):826−833.
30. Bouwstra H, Dijck−Brouwer J, Desci T, et al. Neurologic condition of healthy term infants at 18 months: positive association with venous umbilical DHA status and negative association with umbilical trans−fatty acids. Pediatric Res. 2006;60(3):334−339.
31. Miles EA, Noakes PS, KremmydaLS, et al. The salmon in pregnancy study: study design, subject characteristics, maternal fish and marine n−3 fatty acid intake, and marine n−3 fatty acid staus in maternal and umbilical cord blood. Am J Clin Nutr. 2011;94(Suppl):1986S−1992S.
32. Noakes PS, Vlachava M, Kremmyda LS, et al. Increased intake of oily fish in pregnancy: effects on neonatal immune responses and on clinical outcomes in infants at 6 mo. Am J Clin Nutr. 2012;95(2):395−404.
33. Palmer DJ, Sullivan T, Gold MS, et al. Effect of n−3 long chain polyunsaturated fatty acid supplementation in pregnancy on infants´ allergies in first year of life: randomised controlled trial. Brit Med J. 2012;344:e184.
34. Helland IB, Smith L, Saarem K. Maternal supplementation with very−long−chain n−3 fatty acids during pregnancy and lactation augments children´s IQ at 4 years of age. Pediatrics. 2003;111:e39−e44.
35. Tan ZS, Harris WS, Beiser AS, et al. Red blood cell omega−3 fatty acid levels and markers of accelerated brain aging. Neurology. 2012;78(9):658−664.
36. De Lorgeril M, Salen P, Martin JL, et al. Mediterranean diet, traditional risk factors, and the rate of cardiovascular complications after myocardial infarction. Final report of the Lyon diet heart study. Circulation. 1999; 99(6):779−785.
37. Marchioli R, Barzi F, Bomba E, et al. Early protection against sudden death by n−3 polyunsaturated fatty acids after myocardial infarction: time−course analysis of the results of the Gruppo Italiana per lo Studio della Sopravvivenza nell´infarto Miocardico (GISSI)−Prevenzione. Clinical investigation and reports. Circulation. 2002;105(16):1897−1903.
38. Sekikawa A, Curb JD, Ueshima H, et al. Marine−derived n−3 fatty acids and atherosclerosis in Japanese, Japanese−American, and white men. J Am Coll Cardiol. 2008;52(6):417−424.
39. Lee JH, O´Keefe JH, Lavie CJ, et al. Omega−3 fatty acids for cardioprotection. Mayo Clin Proc. 2008;83(3):324−332.
40. Martinez−Gonzalez MA, Bes−Rastrollo M, et al. Mediterranean food pattern and the primary prevention of chronic disease: recent developments. Nutr Rev. 2009; 67(Suppl.1):111−116.
41. Schwedhelm C, Boeing H, Hoffmann G, et al. Effect of diet on mortality and cancer recurrence among cancer survivors: a systematic review and meta−analysis of cohort studies. Nutr Rev. 2016;74(12):737−748.