Seed oils are ubiquitous in modern diets, especially in processed foods and restaurant meals. While they are widely used due to their affordability and versatility, growing evidence suggests that seed oils can have adverse health effects, particularly by promoting inflammation. This article explores why seed oils cause inflammation, how they are extracted, their impact on the body, and lists common seed oils found in foods.
What Are Seed Oils?
Seed oils are vegetable oils extracted from the seeds of various plants. They are used extensively in cooking, baking, and as ingredients in processed foods due to their neutral flavour and high smoke point.
Common Seed Oils Used in Food
Soybean Oil
Corn Oil
Sunflower Oil
Safflower Oil
Canola Oil (Rapeseed Oil)
Cottonseed Oil
Grapeseed Oil
Rice Bran Oil
How Seed Oils Are Extracted
The extraction process for seed oils typically involves several steps that can significantly alter their natural composition and potentially introduce harmful substances:
Mechanical Pressing: Seeds are cleaned and then crushed to release the oil. This process may involve heating to increase yield, which can degrade the oil’s quality.
Solvent Extraction: Hexane, a chemical solvent, is often used to extract the remaining oil from the seed mash. This method is efficient but can leave chemical residues in the oil.
Refining: The crude oil undergoes refining to remove impurities, including bleaching and deodorising. This process often involves high heat and chemical treatments, which can further degrade the oil and produce trans fats and other unhealthy by-products.
Why Seed Oils Cause Inflammation
High Omega-6 Fatty Acid Content: Seed oils are rich in omega-6 polyunsaturated fatty acids (PUFAs). While omega-6 fatty acids are essential, modern diets tend to have an imbalanced ratio of omega-6 to omega-3 fatty acids. Excessive omega-6 intake can lead to the production of pro-inflammatory eicosanoids, contributing to chronic inflammation.
Oxidation and Free Radicals: The high PUFA content in seed oils makes them prone to oxidation, especially when exposed to heat, light, and air. Oxidised fats can produce free radicals, which damage cells and tissues, leading to inflammation and increased risk of chronic diseases.
Trans Fats: The refining process of seed oils can produce trans fats, which are well-known for their inflammatory properties and negative impact on heart health.
Effects of Seed Oils on the Body
Inflammation: Chronic inflammation is a common denominator in many diseases, including heart disease, diabetes, arthritis, and cancer. The imbalance of omega-6 to omega-3 fatty acids from high seed oil consumption promotes an inflammatory state in the body.
Metabolic Health: Seed oils have been linked to metabolic disorders, including insulin resistance and obesity. Inflammation from omega-6 fatty acids can impair insulin signalling and contribute to metabolic syndrome.
Heart Health: While some studies suggest that PUFAs can lower LDL cholesterol, the inflammatory effects of omega-6 fatty acids and the presence of trans fats can negate these benefits, increasing the risk of cardiovascular diseases.
Oxidative Stress: Oxidation of seed oils can lead to oxidative stress, damaging cells and DNA. This can accelerate ageing and increase the risk of degenerative diseases.
Alternatives to Seed Oils
Given the potential health risks associated with seed oils, it’s beneficial to consider healthier alternatives for cooking and food preparation:
Extra Virgin Olive Oil: Rich in monounsaturated fats and antioxidants, olive oil has anti-inflammatory properties.
Coconut Oil: Contains medium-chain triglycerides (MCTs) that provide quick energy and have antimicrobial effects. Stable at high temperatures.
Avocado Oil: High in monounsaturated fats and vitamin E, avocado oil is good for cooking at high temperatures.
Butter and Ghee: Rich in fat-soluble vitamins and conjugated linoleic acid (CLA). Ghee is lactose-free and has a high smoke point.
Conclusion
Seed oils are prevalent in the modern diet but come with significant health concerns, primarily due to their high omega-6 fatty acid content, tendency to oxidise, and the production of trans fats during processing. These factors contribute to inflammation and various chronic diseases. By understanding the extraction process and the impact of seed oils on the body, individuals can make more informed dietary choices. Opting for healthier oils like extra virgin olive oil, coconut oil, avocado oil, and ghee can help reduce inflammation and promote better overall health.
References
Simopoulos, A. P. (2002). Omega-3 fatty acids in inflammation and autoimmune diseases. Journal of the American College of Nutrition, 21(6), 495-505.
Mozaffarian, D., & Clarke, R. (2009). Quantitative effects on cardiovascular risk factors and coronary heart disease risk of replacing partially hydrogenated vegetable oils with other fats and oils. European Journal of Clinical Nutrition, 63(S2), S22-S33.
Calder, P. C. (2006). Polyunsaturated fatty acids and inflammation. Prostaglandins, Leukotrienes, and Essential Fatty Acids, 75(3), 197-202.
De Souza, R. J., Mente, A., Maroleanu, A., Cozma, A. I., Ha, V., Kishibe, T., ... & Anand, S. S. (2015). Intake of saturated and trans unsaturated fatty acids and risk of all-cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. BMJ, 351, h3978.
Blasbalg, T. L., Hibbeln, J. R., Ramsden, C. E., Majchrzak, S. F., & Rawlings, R. R. (2011). Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century. American Journal of Clinical Nutrition, 93(5), 950-962.