Are Seed Oils Bad For You? Do They Contribute To Inflammation?

Seed oils and their alleged link to inflammation have been recently gaining traction on the internet. This has caused confusion among the general public seeking recommendations to inform what types of oils we should consume and cook with. In this blog, we will explore some of the common seed oils, the top misconceptions arising from the use of seed oils, look at the current scientific evidence and address the demanding question: do seed oils contribute to inflammation and other health complications? 

What are seed oils? 

Seed oils are a broad category of oils including a variety of omega-6 rich vegetable oils that are made from seeds. These commonly include sunflower, safflower, hempseed, grapeseed, soybean and corn oils. 

What are the myths around seed oils and where do they come from? [Let’s debunk!] 

Critics and health influencers have created quite the buzz online, making seed oils appear to be culprits for inflammation, chronic disease/cancer in Western culture and overall poor health. What are their arguments and what does the science/facts have to say about these? 

Critics Argument (Myth) #1: Seed oils are an unsaturated fat so they will become rancid and oxidize. This means they will form free radicals which increases risk of cancer. 

Debunk the myth and Tip #1: Every fat, whether it is saturated or unsaturated, has the potential to become rancid and produce free radicals due to various factors (ie. heat exposure, length of time, light exposure). While it is true that unsaturated fats are more likely to become rancid than saturated fats due their chemical composition, this can be largely avoided by introducing proper storage techniques. This includes: 

• Limiting the amount of oil you purchase to what you can use within a reasonable time frame 
• Buying oils packaged in an opaque container and storing them in cool dark place 

• Not heating the oils at a high temperature for a long time such as in deep fat frying. 

Critics Argument (Myth) #2: Seed oils will increase inflammation and your risk of heart disease. 

Debunk the myth: This myth may stem from the incomplete understanding of the role of Omega-6 fats and its properties in the larger context of the diet. When consumed in moderate amounts, studies do not suggest that there is any significant association between Omega-6s and increased inflammation markers (2) and may even be associated with reduced risk of inflammation (3). The concern arises when there is a significant imbalance of the Omega 6 to Omega 3 ratio , where a much higher consumption of Omega 6s occurs compared to Omega 3s. This is associated with an increase in inflammation markers (1). At present, the Western diet is well above this ratio (around 15:1) given the frequent consumption of highly processed food and higher intakes of Omega 6s (7). To balance your intake of Omega 6s and Omega 3s: 

• Aim for a lower Omega 6 to 3 ratio (closer to the ideal ratio of 4:1) and/or focus on increasing intaking of Omega 3-fats. Oils consisting of better ratios include olive oil, flaxseed oil, and hempseed oil. 
• Follow Canada’s Food Guide recommendation of having 2-3 tablespoons of unsaturated fats per day. 

The verdict 

Seed oils have undeservingly been given a bad name but scientific evidence supports that seed oils are NOT inflammatory, especially when consumed in moderation as part of an overall well-balanced diet. It is important to be choosing sources that are close to the ideal Omega 6 to Omega 3 ratio of 4:1 (or having more Omega 3 fats compared to Omega 6 fats), having moderate amounts of all fats, diversifying the types of oils in your diet, and choosing unsaturated fats more often than saturated fats. For those with different nutritional needs, always ask a health professional such as a dietitian who can help you come up with a plan to meet well-balanced and sustainable nutrition. 

References 

1. Simopoulos, A. P. (2016). An increase in the omega-6/omega-3 fatty acid ratio increases the risk for obesity. Nutrients, 8(3), 128.
2. Su, H., Liu, R., Chang, M., Huang, J., & Wang, X. (2017). Dietary linoleic acid intake and blood inflammatory markers: a systematic review and meta-analysis of randomized controlled trials. Food & function, 8(9), 3091-3103.
3. Marklund, M., Wu, J. H., Imamura, F., Del Gobbo, L. C., Fretts, A., De Goede, J., ... & Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Fatty Acids and Outcomes Research Consortium (FORCE). (2019). Biomarkers of dietary omega-6 fatty acids and incident cardiovascular disease and mortality: an individual-level pooled analysis of 30 cohort studies. Circulation, 139(21), 2422-2436.
4. Amiri, M., Raeisi-Dehkordi, H., Sarrafzadegan, N., Forbes, S. C., & Salehi-Abargouei, A. (2020). The effects of Canola oil on cardiovascular risk factors: A systematic review and meta-analysis with dose-response analysis of controlled clinical trials. Nutrition, Metabolism and Cardiovascular Diseases, 30(12), 2133-2145.
5. Pourrajab, B., Sharifi-Zahabi, E., Soltani, S., Shahinfar, H., & Shidfar, F. (2022). Comparison of canola oil and olive oil consumption on the serum lipid profile in adults: a systematic review and meta-analysis of randomized controlled trials. Critical Reviews in Food Science and Nutrition, 1-15.
6. 6.Ghobadi, S., Hassanzadeh-Rostami, Z., Mohammadian, F., Zare, M., & Faghih, S. (2019). Effects of canola oil consumption on lipid profile: A systematic review and meta-analysis of randomized controlled clinical trials. Journal of the American College of Nutrition, 38(2), 185-196.7.  

7. Simopoulos, A. P. (2006). Evolutionary aspects of diet, the omega-6/omega-3 ratio and genetic variation: nutritional implications for chronic diseases. Biomedicine & pharmacotherapy, 60(9), 502-507.
8. "FoodData Central Search Results Oil, corn, industrial and retail, all purpose salad or cooking." USDA Department of Agriculture, 2019, fdc.nal.usda.gov/fdc-app.html#/food-details/171029/nutrients.

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