Until 1929, scientists did not consider fatty acids like omega-3s to be much more than a source of calories.[7] In a monumental report, George and Mildred Burr shone the first light on fatty acids as essential nutrients required to maintain health. Almost a century later, hundreds of studies on fatty acids and their role in human health make up a library of knowledge on these essential nutrients. 

Fish oil as a source of omega-3 fatty acids is one of the most popular nonvitamin/nonmineral dietary supplements used by both adults and children.[17] Omega-3 fatty acids are associated with reducing the risk of coronary heart disease, mental abnormalities, and developmental disorders. [8-10]



In the human body, the brain and retinas are loaded with omega-3 fatty acids (ALA, EPA, DHA), building the phospholipid structures of the cell membrane. Various functions of omega-3s include:

  • Signal transduction[11, 12]

  • Energy source[11, 12]

  • Regulation of cardiovascular, pulmonary, immune, and endocrine systems[9, 12-15]

ALA is an essential fatty acid and is the precursor for both EPA and DHA. ALA must be obtained from the diet, as the body cannot make ALA on its own. ALA is associated with neuroprotection, vasodilation of arteries, and neuroplasticity.[16] Dietary sources of ALA include fish/seafood and plant oils like flaxseed, soybean, and canola oils.[17]

EPA is associated with a positive effect on emotional balance.[10, 18] Just fifteen percent of ALA turns into EPA, and even a smaller amount is eventually converted to DHA.[17] DHA is the most abundant omega-3 in the brain. It is a major component of the neuronal membrane and plays an important role in normal brain structure. 

Both EPA and DHA are precursors for resolvins, molecules named for their role in resolving the inflammatory response.[19] Specifically, some studies have shown that supplementation with EPA and DHA is associated with:

  • Decreased markers of inflammation[8, 9]

  • Reduced risk of new blood vessel formation in the retina[20]

  • Healthy cognitive function in elderly patients[21]

  • Improved vascular preservation

  • Reduced risk of heart disease[22, 23]

A balanced dietary intake ratio of omega-6s and omega-3s reduces inflammatory activity and is associated with reduced risk of chronic conditions like cardiovascular disease and cancer.[17] Although there is no clear consensus on the proper ratio of omega-6 to omega3, it is prudent to ensure that the dietary intake of omega-6 to omega-3 ratio not exceed 4:1. Unfortunately, the intake ratio of omega-6 to omega-3 in the United States is estimated to be as high as 20:1.[24] 

The National Academy of Medicine established adequate intake (AI) levels for omega-3 fatty acids as follows:
[17]

According to 2011–2012 National Health and Nutrition Examination Survey (NHANES) data, the majority of children and adults in the United States consume recommended amounts of omega-3 fatty acids in the form of ALA, but with low amounts of DHA and EPA. For valuable information on fatty acids and their role in inflammation, click here.

While the average Western diet tends to favor saturated, monounsaturated, and omega-6 polyunsaturated fatty acids, a lifestyle change with increased fish and seafood consumption, and supplementation with omega-3 fatty acids when needed can address suboptimal dietary intake of these key fatty acids.[25] These lifestyle changes could tip the balance in favor of omega-3s, welcoming in the plethora of health benefits that accompany these fatty acids. 
 

References
1.    Facts about saturated fats. MedlinePlus, 2018.
2.    Artificial trans fats banned in U.S. 2018.
3.    Facts about trans fats. MedlinePlus, 2018.
4.    Facts about monounsaturated fats. MedlinePlus, 2018.
5.    Facts about polyunsaturated fats. MedlinePlus, 2018.
6.    Hu, F.B., et al., Dietary fat intake and the risk of coronary heart disease in women. N Engl J Med, 1997. 337(21): p. 1491-9.
7.    Spector, A.A. and H.Y. Kim, Discovery of essential fatty acids. J Lipid Res, 2015. 56(1): p. 11-21.
8.    Dangardt, F., et al., Omega-3 fatty acid supplementation improves vascular function and reduces inflammation in obese adolescents. Atherosclerosis, 2010. 212(2): p. 580-5.
9.    Allaire, J., et al., A randomized, crossover, head-to-head comparison of eicosapentaenoic acid and docosahexaenoic acid supplementation to reduce inflammation markers in men and women: the Comparing EPA to DHA (ComparED) Study. Am J Clin Nutr, 2016. 104(2): p. 280-7.
10.    Agriculture., U.S.D.o.H.a.H.S.a.U.S.D.o., 2015 – 2020 Dietary Guidelines for Americans. , U.S.D.o.H.a.H.S.a.U.S.D.o. Agriculture., Editor. 2015.
11.    Institute of Medicine, F.a.N.B., Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients). 2005, National Academy Press: Washington, D.C.
12.    SanGiovanni, J.P. and E.Y. Chew, The role of omega-3 long-chain polyunsaturated fatty acids in health and disease of the retina. Prog Retin Eye Res, 2005. 24(1): p. 87-138.
13.    Calder, P.C., Omega-3 fatty acids and inflammatory processes: from molecules to man. Biochem Soc Trans, 2017. 45(5): p. 1105-1115.
14.    Simopoulos, A.P., The importance of the omega-6/omega-3 fatty acid ratio in cardiovascular disease and other chronic diseases. Exp Biol Med (Maywood), 2008. 233(6): p. 674-88.
15.    van Gelder, B.M., et al., Fish consumption, n-3 fatty acids, and subsequent 5-y cognitive decline in elderly men: the Zutphen Elderly Study. Am J Clin Nutr, 2007. 85(4): p. 1142-7.
16.    Blondeau, N., et al., Alpha-linolenic acid: an omega-3 fatty acid with neuroprotective properties-ready for use in the stroke clinic? Biomed Res Int, 2015. 2015: p. 519830.
17.    Omega-3 Fatty Acids. National Institutes of Health Office of Dietary Supplements, 2018.
18.    Grosso, G., et al., Role of omega-3 fatty acids in the treatment of depressive disorders: a comprehensive meta-analysis of randomized clinical trials. PLoS One, 2014. 9(5): p. e96905.
19.    Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA). Nutrition and Traumatic Brain Injury: Improving Acute and Subacute Health Outcomes in Military Personnel
ed. M.O. J. Erdman, L. Pillsbury. 2011, Washington, D.C.: National Academies Press (US).
20.    Sapieha, P., et al., 5-Lipoxygenase metabolite 4-HDHA is a mediator of the antiangiogenic effect of omega-3 polyunsaturated fatty acids. Sci Transl Med, 2011. 3(69): p. 69ra12.
21.    Dyall, S.C., Long-chain omega-3 fatty acids and the brain: a review of the independent and shared effects of EPA, DPA and DHA. Front Aging Neurosci, 2015. 7: p. 52.
22.    Harris, W.S., P.M. Kris-Etherton, and K.A. Harris, Intakes of long-chain omega-3 fatty acid associated with reduced risk for death from coronary heart disease in healthy adults. Curr Atheroscler Rep, 2008. 10(6): p. 503-9.
23.    Kris-Etherton, P.M., W.S. Harris, and L.J. Appel, Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation, 2002. 106(21): p. 2747-57.
24.    Simopoulos, A.P., An Increase in the Omega-6/Omega-3 Fatty Acid Ratio Increases the Risk for Obesity. Nutrients, 2016. 8(3): p. 128.
25.    M.L. Garg, L.G.W., H. Singh, and P.J. Moughan, Means of Delivering Recommended Levels of Long Chain n-3 Polyunsaturated Fatty Acids in Human Diets. Journal of Food Science, 2006. 71(5): p. 6.
26.    Levantesi, G., M.G. Silletta, and R. Marchioli, Uses and benefits of omega-3 ethyl esters in patients with cardiovascular disease. J Multidiscip Healthc, 2010. 3: p. 79-96.