The Importance of the Omega-6/Omega-3 Ratio to Human Health

Because the media has hyped the benefits of omega-3 fatty acids so frequently, most people are aware of the advantages of consuming fish oil or omega-3 supplements. However, many people are not aware that this represents only half the story.

Human beings evolved to consume a diet comprising approximately a 1:1 ratio of omega-6 to omega-3 essential fatty acids. In Western diets, however, that ratio can be 15-to-1 or even greater [1]. This discrepancy is a result of both underconsumption of omega-3 fatty acids and an overconsumption of omega-6 fatty acids.

One of the main tenets of a Paleolithic diet is to provide our bodies with foods that match our genetically determined nutritional requirements. Dietary mismatches can cause health concerns. This is particularly true with our fatty acid ratios. The high omega-6 to omega-3 ratio in Western diets has been shown to promote the pathogenesis of many diseases, including cardiovascular disease [2] [3], cancer [4] [5], and inflammatory [6] and autoimmune diseases [1].

The basics of fatty acids

Omega-6 and omega-3 fatty acids are the two biologically important subgroups of polyunsaturated fatty acids. These compounds get their name because they contain two or more double bonds along their carbon backbone.

While we store most of the fatty acids that we eat as triglycerides in our fat cells, fatty acids are also incorporated into all cell membranes. The membrane, or border of the cell, is made up of compounds called phospholipids. Phospholipids consist of the fatty acids we consume.

Importantly, the ratio of omega-6 to omega-3 fatty acids in our diet is reflected in the ratio in our cell membranes. The correct functioning of our cells requires the same ratio to which humans evolved. Therefore, the omega-6 to omega-3 ratio is implicated in so many different diseases; a deficiency in this ratio can affect any cell in the body.

There are many forms of omega-6 and omega-3 fatty acids, but humans can only use a few forms. Fortunately, it is possible to convert between the different forms in the liver. The bioactive forms have what are called “parent” fatty acids; the liver can make the bioactive forms of omega-6 and omega-3 fatty acids from these “parent” forms.

Because our bodies cannot synthesize the parent form, they are also often referred to as essential fatty acids. The parent for the omega-3 family is called alpha linolenic acid (18:3n-3; ALA); the omega-6 parent is linoleic acid (18:2n-6; LA). To make them useable by the body, both parent fatty acids are converted in the liver by two processes called desaturation
and chain-elongation.

However, the conversion of dietary 18 carbon polyunsaturated fatty acids (PUFA) to longer-chain (> 20 carbon atoms in length) PUFA is an inefficient process. Only about 6 percent of ALA is converted to eicosapentaenoic acid (20:5n-3; EPA) and less still (3.8 percent) is converted to the usable form, docosahexaenoic acid (22:6n-3; DHA).

Furthermore, because omega-3 and omega-6 parent fatty acids must compete for the same enzymes to desaturate and elongate, a high dietary intake of omega-6 fatty acids (18:2n-6) can further reduce the conversion of ALA to EPA and DHA by 40 to 50 percent. In other words, consuming excessive amounts of omega-6 fatty acids reduces the bioavailable form of omega-3s. So, it is important to consume sufficient omega-3 fatty acids and not overconsume omega-6 fatty acids.

Fatty acids, eicosanoids, and inflammatory diseases

There are several physiological reasons why a host of diseases can be caused by, or exacerbated by, an imbalance of omega-6 and omega-3 fatty acids. One of the most crucial reasons stems from the synthesis of a type of hormone called eicosanoids, which play a crucial role in the inflammatory response.

Eicosanoids are synthesized from the fatty acids in cell membranes, and both their form and function depend on the balance of omega-3 and omega-6 fatty acids in the membrane. Eicosanoids produced from the omega-3 fatty acids (20:5n-3 or EPA) tend to be anti-inflammatory, whereas eicosanoids derived from omega-6 fatty acids (20:4n-6 or arachidonic acid) may promote inflammation in certain tissues.

In fact, many over-the-counter pain killers simply block omega-6 derived eicosanoid activity. Because of the imbalance in the omega-6/omega-3 ratio in the typical Western diet, a chronic state of low-grade inflammation can exist, which in turn may promote many health disorders and diseases [6].

Since the brain primarily consists of fatty acids, the omega-6 to omega-3 ratio has a significant influence on brain function, dementia, and related conditions.

The effects of PUFA on brain function can be divided into at least five categories: 1) modification of neuronal membrane fluidity; 2) modification of membrane activity-bound enzymes; 3) modification of the number and affinity of receptors; 4) modification of the function of neuronal membrane ionic channels; and 5) modification of the production of neurotransmitters and brain peptides [7].

Researchers often look at the absolute quantity of omega-3 fatty acids as well as the ratio of omega-3 to omega-6 fatty acids when conducting this type of research. In one study of individuals 55 years of age and above, it was found that there was a positive association to improved cognitive performance between a higher absolute volume of omega-3s in red blood cells and a lower ratio (closer to 1:1) of omega-6 to omega-3s [8].

Furthermore, cognitive impairment is a common consequence of epilepsy in children. A study aimed at assessing the impact of the ratio of omega-6 to omega-3 fatty acid levels on cognitive function in children with idiopathic epilepsy demonstrated that those with epilepsy had lower levels of omega-3s and higher levels of omega-6 fatty acids; they also had an abnormal omega-6 to omega-3 ratio compared to non-epileptic children [9].

Other research makes clear that the impact of the omega-6/omega-3 ratio can’t be overstated. It has been shown that a high ratio negatively influences depression and inflammatory diseases [10], obesity [11], clinical pain, and functional limitations in adults with knee pain [12], cord plasma levels with more child attention deficit and hyperactivity disorder (ADHD) symptoms [13], and gout [14].

Conclusion

There are those that feel too much emphasis is being placed on the omega-6 to omega-3 ratio, and argue that, while it is not equal to that of our ancestors, it is also not as high as previously thought. They argue that the ratio is less important than the amount of EPA and DHA in our diets [15] [16].

That’s why following The Paleo Diet®® is a great approach. Not only do you match the omega-6 to omega-3 ratio of our ancestors, but you also consume healthy amounts of EPA and DHA.

References

[1] Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother 2002;56:365–79. https://doi.org/10.1016/s0753-3322(02)00253-6.

[2] DiNicolantonio JJ, OKeefe J. Importance of maintaining a low omega-6/omega-3 ratio for reducing platelet aggregation, coagulation and thrombosis. Open Hear 2019;6:e001011. https://doi.org/10.1136/openhrt-2019-001011.

[3] Serra MC, Ryan AS, Hafer-Macko CE, Yepes M, Nahab FB, Ziegler TR. Dietary and Serum Omega-6/Omega-3 Fatty Acids Are Associated with Physical and Metabolic Function in Stroke Survivors. Nutrients 2020;12:701. https://doi.org/10.3390/nu12030701.

[4] Kobayashi N, Barnard RJ, Henning SM, Elashoff D, Reddy ST, Cohen P, et al. Effect of Altering Dietary ω-6/ω-3 Fatty Acid Ratios on Prostate Cancer Membrane Composition, Cyclooxygenase-2, and Prostaglandin E2. Clin Cancer Res 2006;12:4662–70. https://doi.org/10.1158/1078-0432.ccr-06-0459.

[5] Kang JX, Liu A. The role of the tissue omega-6/omega-3 fatty acid ratio in regulating tumor angiogenesis. Cancer Metast Rev 2013;32:201–10. https://doi.org/10.1007/s10555-012-9401-9.

[6] DiNicolantonio JJ, O’Keefe JH. Importance of maintaining a low omega–6/omega–3 ratio for reducing inflammation. Open Hear 2018;5:e000946. https://doi.org/10.1136/openhrt-2018-000946.

[7] Yehuda S. Omega-6/Omega-3 Ratio and Brain-Related Functions. World Rev Nutr Diet 2003;92:37–56. https://doi.org/10.1159/000073791.

[8] Nunes B, Pinho C, Sousa C, Melo AR, Bandarra N, Silva MC. Relevance of Omega-3 and Omega-6 / Omega-3 Ratio in Preventing Cognitive Impairment. Acta Médica Portuguesa 2016;30:213–23. https://doi.org/10.20344/amp.7970.

[9] Bahagat KA, Elhady M, Aziz AA, Youness ER, Zakzok E. Cociente omega-6/omega-3 y cognición en niños con epilepsia. Anales De Pediatría 2019;91:88–95. https://doi.org/10.1016/j.anpedi.2018.07.015.

[10] Kiecolt-Glaser JK, Belury MA, Porter K, Beversdorf DQ, Lemeshow S, Glaser R. Depressive Symptoms, omega-6:omega-3 Fatty Acids, and Inflammation in Older Adults. Psychosom Med 2007;69:217–24. https://doi.org/10.1097/psy.0b013e3180313a45

[11] Simopoulos AP. An Increase in the Omega-6/Omega-3 Fatty Acid Ratio Increases the Risk for Obesity. Nutrients 2016;8:128. https://doi.org/10.3390/nu8030128.

[12] Sibille KT, King C, Garrett TJ, Glover TL, Zhang H, Chen H, et al. Omega-6. Clin J Pain 2018;34:182–9. https://doi.org/10.1097/ajp.0000000000000517.

[13] Serra MC, Ryan AS, Hafer-Macko CE, Yepes M, Nahab FB, Ziegler TR. Dietary and Serum Omega-6/Omega-3 Fatty Acids Are Associated with Physical and Metabolic Function in Stroke Survivors. Nutrients 2020;12:701. https://doi.org/10.3390/nu12030701.

[14] Zhang M, Zhang Y, Terkeltaub R, Chen C, Neogi T. Effect of Dietary and Supplemental Omega‐3 Polyunsaturated Fatty Acids on Risk of Recurrent Gout Flares. Arthritis Rheumatol 2019;71:1580–6. https://doi.org/10.1002/art.40896.

[15] Sheppard KW, Cheatham CL. Omega-6/omega-3 fatty acid intake of children and older adults in the U.S.: dietary intake in comparison to current dietary recommendations and the Healthy Eating Index. Lipids Health Dis 2018;17:43. https://doi.org/10.1186/s12944-018-0693-9.

[16] Harris WS. The Omega-6:Omega-3 Ratio: A Critical Appraisal and Possible Successor. Prostaglandins Leukot Essent Fat Acids 2018;132:34–40. https://doi.org/10.1016/j.plefa.2018.03.003.