Omega-6s vs. Omega-3s: Why the Ratio Matters

Both omega-6s and omega-3s belong to a class of fats called polyunsaturated fats, and our bodies require both types—in the proper ratio—to function properly. Both types are integral parts of our cell membranes and affect their fluidity, flexibility, and ability to function in a healthy way. They also modulate inflammatory processes in our bodies, with omega-3s being more anti-inflammatory and omega-6s generally being more pro-inflammatory.³ Omega-6s are not innately bad—it’s the large amounts that we consume, in the absence of omega-3s, that make them unhealthy. 

While humans once consumed a ratio of about 4:1 or less of omega-6 to omega-3, that ratio has shifted to 20:1, or higher.⁴ Modern day humans eat a diet that is deficient in anti-inflammatory omega-3s and is skewed toward an excessive amount of pro-inflammatory omega-6s, particularly in the form of processed vegetable oils. This promotes low-grade inflammation and oxidative stress, which may eventually lead to the development of diseases like cardiovascular disease, cancer, and inflammatory and autoimmune diseases.^{5 6} Consider these numbers: A ratio of 4:1 of omega-6 to omega-3 was associated with a 70 percent decrease in mortality associated with cardiovascular disease; a ratio of 2.5:1 reduced cell proliferation in patients with colorectal cancer; a ratio of 5:1 had a beneficial effect on patients with asthma; and a ratio of 2-3:1 suppressed inflammation in patients with rheumatoid arthritis.⁷ The takeaway? A lower omega-6 to omega-3 ratio is supportive of overall health. 

 The Heart of the Matter

Vegetable oils are promoted as “heart healthy,” in part because they were shown in early studies to lower cholesterol. However, we now know that cholesterol is not the main driver of cardiovascular disease and new analyses of research show a more complex reality. Take for example the Minnesota Coronary Experiment (MCE), conducted from 1968 to 1973. This trial reported that replacing saturated fat with vegetable oil (specifically corn oil) reduced coronary heart disease and death by lowering serum cholesterol. But a fresh analysis of the study, published in 2016, reviewed unpublished data on the 9,423 participants of the MCE and found that while replacing saturated fats with vegetable oils did indeed lower cholesterol levels, there was “no mortality benefit for the intervention group.” And in fact, “There was a 22% higher risk of death for each 30 mg/dL reduction in serum cholesterol…” and “There was no evidence of benefit in the intervention group for coronary atherosclerosis or myocardial infarcts [heart attacks].” In analyses of other studies, “these cholesterol lowering interventions showed no evidence of benefit on mortality from coronary heart disease or all-cause mortality.” The researchers concluded by saying that findings from the Minnesota Coronary Experiment “add to growing evidence that incomplete publication has contributed to overestimation [of benefits], and underestimation of potential risks, of replacing saturated fat with vegetable oils rich in linoleic acid [the main omega-6 found in vegetable oil].”⁸

A review published in 2018 in the journal Open Heart presented research that showed vegetable oils high in omega-6 fats may actually drive the development of atherosclerosis and coronary heart disease in part by promoting oxidative damage and inflammation in the endothelium (the lining of our blood vessels) and increasing the oxidation of LDL cholesterol.⁹ Other research has similar findings, showing that the consumption of vegetable oils high in omega-6s increase inflammation in the aorta and endothelium, contribute to low-grade inflammation, oxidative stress, and endothelial dysfunction.¹⁰

Omega-6 a Root Cause of Degenerative Diseases

A 2020 review investigated vegetable oil’s potential role in the development of lifestyle diseases including obesity, type-2 diabetes, non-alcoholic fatty liver disease, and Alzheimer’s by increasing damage to cells. The review describes how vegetable oils like corn, soybean, and sunflower create a substance called hydroxynonenal when heated, which researchers believe plays a key role in cell degeneration and death. Further, even vegetable oils that are not deep fried (like those found in mayonnaise, salad dressing, etc.) will be incorporated into cell membranes and LDL cholesterol, where they increase inflammation and oxidative damage. The researchers conclude that decreasing the consumption of omega-6 oils while increasing the consumption of omega-3 oils is critical in preventing various lifestyle diseases.¹¹ This is key because both types of fat compete for space in cell membranes; in other words, if you are consuming more omega-6 fats compared to omega-3 fats, your cell membranes will mostly be comprised of pro-inflammatory omega-6s. 

Find a Healthy Balance

As with most things in life, balance is key. Start reading labels—once you start looking for vegetable oils, you will find them everywhere (I recently found soybean oil in the ingredient list of Italian sausage). In general, most processed foods (packaged snacks, cookies, salad dressings, crackers, chips, etc.) will contain some type of vegetable oil. The same goes for fast food and restaurant food. Avoid these as much as possible. At home, choose oils such as coconut oil, butter, high-oleic sunflower or high-oleic safflower oils, and extra virgin olive oil for cooking. In general, look for oils that contain a higher amount of saturated and/or monounsaturated fat in relation to polyunsaturated fats (which are typically omega-6). Last but not least, take a quality omega-3 fish oil supplement. The large majority of us simply don’t eat enough cold-water fatty fish (one of the main food sources of omega-3s) to get optimal amounts. A supplement will ensure that you saturate your cell membranes with the good stuff! 

A Note On Omega-9 Fats

While much focus is on the omega-6 and omega-3 fatty acids, omega-9 is another important one to know. Omega-9 fats are a type of monounsaturated fatty acid and have their own health benefits including supporting cardiovascular health and a healthy weight; the most common omega-9 fat is oleic acid. Olive oil is one of the best-known sources, containing 55 to 83 percent oleic acid.¹² High-oleic sunflower and safflower oils are specifically made to reduce omega-6 content while increasing omega-9 as oleic acid; they typically contain a minimum of 80 percent oleic acid. Be sure to look for “high-oleic”—regular sunflower and safflower oils are very high in omega-6 fats. When checking the nutrition label, look for a higher amount of monounsaturated fat (omega-9) versus polyunsaturated fat (typically omega-6). These oils are healthy alternatives to high omega-6 oils like corn, soybean, and canola oils.

References

1. Yamashima T, Ota T, Mizukoshi E, et al. “Intake of Omega-6 Polyunsaturated Fatty Acid-Rich Vegetable Oils and Risk of Lifestyle Diseases.” Advances in Nutrition, Nov 202; Vol11 (6). https://doi.org/10.1093/advances/nmaa072
2. DiNicolantonio JJ, O’Keefe JH. Omega-6 vegetable oils as a driver of coronary heart disease: the oxidized linoleic acid hypothesis. Open Heart 2018;5:e000898. doi: 10.1136/openhrt-2018-000898
3. Djuricic I, Calder PC. Beneficial Outcomes of Omega-6 and Omega-3 Polyunsaturated Fatty Acids on Human Health: An Update for 2021. Nutrients. 2021 Jul 15;13(7):2421. doi: 10.3390/nu13072421.
4. DiNicolantonio, J. J., & O'Keefe, J. (2021). The Importance of Maintaining a Low Omega-6/Omega-3 Ratio for Reducing the Risk of Autoimmune Diseases, Asthma, and Allergies. Missouri medicine, 118(5), 453–459.
5. DiNicolantonio JJ, O’Keefe JH Importance of maintaining a low omega–6/omega–3 ratio for reducing inflammation Open Heart 2018;5:e000946. doi: 10.1136/openhrt-2018-000946
6. Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002 Oct;56(8):365-79. doi: 10.1016/s0753-3322(02)00253-6.
7. Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002 Oct;56(8):365-79. doi: 10.1016/s0753-3322(02)00253-6.
8. Ramsden CE, Zamora D, Majchrzak-Hong S, et al. “Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-1973). BMJ 2016; 353:i1246 doi: https://doi.org/10.1136/bmj.i1246
9. DiNicolantonio JJ, O’Keefe JH Omega-6 vegetable oils as a driver of coronary heart disease: the oxidized linoleic acid hypothesis Open Heart 2018;5:e000898. doi: 10.1136/openhrt-2018-000898
10. DiNicolantonio JJ, O’Keefe JH Importance of maintaining a low omega–6/omega–3 ratio for reducing inflammation Open Heart 2018;5:e000946. doi: 10.1136/openhrt-2018-000946
11. Yamashima T, Ota T, Mizukoshi E, Nakamura H, Yamamoto Y, Kikuchi M, Yamashita T, Kaneko S. Intake of ω-6 Polyunsaturated Fatty Acid-Rich Vegetable Oils and Risk of Lifestyle Diseases. Adv Nutr. 2020 Nov 16;11(6):1489-1509. doi: 10.1093/advances/nmaa072.
12. Hernández, M. L., Sicardo, M. D., Belaj, A., & Martínez-Rivas, J. M. (2021). The Oleic/Linoleic Acid Ratio in Olive (Olea europaea L.) Fruit Mesocarp Is Mainly Controlled by OeFAD2-2 and OeFAD2-5 Genes Together With the Different Specificity of Extraplastidial Acyltransferase Enzymes. Frontiers in Plant Science, 12. https://doi.org/10.3389/fpls.2021.653997