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Cracking the Seed Oil Code: What You Should Know

Despite extensive research spanning decades, the public’s understanding of fats remains varied. Social media health influencers assert that seed oils possess toxic qualities, attributing them to a range of issues, including inflammation, acne, weight gain, cancer, and infertility. However, delving into the actual science reveals a much more nuanced perspective, often obscured by the simplified narratives.

Seed oils are plant-based oils made from the seeds of various plants like canola, corn, cottonseed, grapeseed, rice bran, safflower, soy, and sunflower. Seed oils contain a significant amount of Omega-6 polyunsaturated fatty acids (PUFAs), with linoleic acid being a key player. These are essential nutrients which means we need to obtain them from our diet.  In fact, the American Heart Association and other health experts recommend the best way to improve the ratio of Omega-6: omega-3 is to increase your Omega-3 intake rather than decrease your omega-6 intake.

Seed Oils – Filtering Out the Truth

Inflammation

Research has debunked the idea that Omega-6s, found in seed oils, are bad for our health. A common misconception is that linoleic acid might trigger chronic inflammation, a root cause of many diseases. Human research has found that linoleic acid isn’t inflammatory overall [1]. Also, only a tiny fraction (0.2%) of linoleic acid converts to arachidonic acid, a building block for inflammatory compounds [2]. The body needs arachidonic acid to both initiate and terminate inflammation, and studies have shown that Omega-6 fatty acid intake is associated with lower levels of bodily inflammation [3]. A meta-analysis looking at 30 studies encompassing results from over 1,377 participants found that increased dietary linoleic acid did not have any significant impact on blood levels of inflammatory markers [4].

Heart Health

Scientists found that higher levels of linoleic and arachidonic acid levels are not associated with a higher risk of heart disease [5]. In fact, people with higher amounts of linoleic acid in their bloodstream were 7 percent less likely to develop heart disease. Another study [6] followed nearly 2,500 men for an average of 22 years and found that those with the highest blood levels of linoleic acid had a 43 percent lower risk of dying from any disease during the study period than those with the lowest. The same dataset showed that higher blood levels of arachidonic acid reduced the risk of dying by 20 percent. Moderate linoleic acid intake reduces blood total cholesterol and low-density lipoprotein (LDL)-cholesterol concentrations [7]. Additionally, increasing intake of arachidonic acid up to 1500 mg/day seems to have no adverse effects on various health markers like platelet aggregation and blood clotting but may benefit muscle and cognitive performance [2].

Linoleic Acid

Linoleic acid is essential because our bodies can’t produce it on their own, so we need to get it from our diet. It has a unique role in the skin’s structural integrity and barrier function because it is an essential constituent of ceramides, major lipid constituents in the upper part of the skin [8]. Skin barrier function depends on the linoleic acid content, and other fatty acids seem unable to substitute for LA in this role.

Arachidonic Acid

Not only is arachidonic acid a building block for compounds that fight inflammation, but it also contributes up to 25% of the fatty acids in phospholipids of skeletal muscles, brain, liver, platelets, and immune cells. Besides immune response, arachidonic acid is vital in wound healing [9], muscle repair, and growth after exercise [10]. Arachidonic acid levels in tissue remain constant despite different quantities of linoleic acid intake [11].

All About Balance

While the research has debunked the idea that seed oils are bad for health, over the past 50 years, omega-6 fatty acid consumption, especially in the United States, has surged by 2.5 times [12] . The key is finding the right balance between Omega-3 and Omega-6 rather than blaming seed oils alone.

Liquid plant oils have been recommended by the Dietary Guidelines for Americans and many scientific societies (such as the American Heart Association and the American Diabetes Association) because of their health benefits. No solid evidence supports the idea that seed oils are toxic and should be avoided entirely. Instead, the focus should be on achieving an optimal balance of Omega-3 and Omega-6 within a healthy diet, considering their potential benefits on inflammation and overall well-being. However, scientists are still debating what that ratio should be [13].

Saturated fat, categorized as an unhealthy dietary fat along with trans-fat, is typically solid at room temperature and is found in foods like butter, palm and coconut oils, cheese, and red meat. It is advisable to choose foods higher in healthier fats, such as monounsaturated and polyunsaturated fats, which are typically liquid at room temperature. It is recommended that no more than 25% to 30% of daily calories come from fats, with saturated fat limited to less than 10% to prevent potential health issues like heart disease [7]. Studies have shown that replacement of 5% energy as saturated fatty acids by linoleic acid was associated with a 9% reduction in coronary heart disease [14].

Summary

Navigating through social media, podcasts, and the internet for nutrition and health information can be tricky. Scientific evidence contradicts claims circulating on social media and the internet that seed oils like canola and soy are “toxic.” Instead, emphasis should be placed on maintaining a balanced ratio between Omega-3 and Omega-6, rather than solely attributing health concerns to seed oils. Finally, while this article focuses on Omega-6 fatty acids, one must remember that the seed oils are not all the same. For example, canola oil averages about 60% oleic acid (Omega-9), 20% linoleic acid and 10% arachidonic acid.

 

Author: Maciej Chichlowski PhD, PMP


 

References

  1. Harris, W.S., The omega-6/omega-3 ratio and cardiovascular disease risk: uses and abuses. Curr Atheroscler Rep, 2006. 8(6): p. 453-9.
  2. Djuricic, I. and P.C. Calder, Beneficial Outcomes of Omega-6 and Omega-3 Polyunsaturated Fatty Acids on Human Health: An Update for 2021. Nutrients, 2021. 13(7).
  3. Fritsche, K.L., The science of fatty acids and inflammation. Adv Nutr, 2015. 6(3): p. 293s-301s.
  4. Su, H., et al., Dietary linoleic acid intake and blood inflammatory markers: a systematic review and meta-analysis of randomized controlled trials. Food Funct, 2017. 8(9): p. 3091-3103.
  5. Marklund, M., et al., Biomarkers of Dietary Omega-6 Fatty Acids and Incident Cardiovascular Disease and Mortality. Circulation, 2019. 139(21): p. 2422-2436.
  6. Virtanen, J.K., et al., Serum n-6 polyunsaturated fatty acids and risk of death: the Kuopio Ischaemic Heart Disease Risk Factor Study. Am J Clin Nutr, 2018. 107(3): p. 427-435.
  7. Mensink, R.P., et al., Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials. Am J Clin Nutr, 2003. 77(5): p. 1146-55.
  8. Rabionet, M., K. Gorgas, and R. Sandhoff, Ceramide synthesis in the epidermis. Biochim Biophys Acta, 2014. 1841(3): p. 422-34.
  9. Silva, J.R., et al., Wound Healing and Omega-6 Fatty Acids: From Inflammation to Repair. Mediators Inflamm, 2018. 2018: p. 2503950.
  10. Tallima, H. and R. El Ridi, Arachidonic acid: Physiological roles and potential health benefits – A review. J Adv Res, 2018. 11: p. 33-41.
  11. Rett, B.S. and J. Whelan, Increasing dietary linoleic acid does not increase tissue arachidonic acid content in adults consuming Western-type diets: a systematic review. Nutr Metab (Lond), 2011. 8: p. 36.
  12. DiNicolantonio, J.J. and J.H. O’Keefe, Omega-6 vegetable oils as a driver of coronary heart disease: the oxidized linoleic acid hypothesis. Open Heart, 2018. 5(2): p. e000898.
  13. Harris, W.S., et al., Omega-6 fatty acids and risk for cardiovascular disease: a science advisory from the American Heart Association Nutrition Subcommittee of the Council on Nutrition, Physical Activity, and Metabolism; Council on Cardiovascular Nursing; and Council on Epidemiology and Prevention. Circulation, 2009. 119(6): p. 902-7.
  14. Farvid, M.S., et al., Dietary linoleic acid and risk of coronary heart disease: a systematic review and meta-analysis of prospective cohort studies. Circulation, 2014. 130(18): p. 1568-78.

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