The Hidden Health Effects of Seed Oils: What You Need to Know
Nutrition
What It Is
Seed oils, often referred to as industrial seed oils, are a type of vegetable oil derived from seeds through processes involving mechanical pressing, solvent extraction, and chemical refining. These oils are ubiquitous in processed foods, making up a significant portion of the average American’s diet. The common sources of seed oils, often called the "hateful eight," include soybean, canola, sunflower, cottonseed, safflower, corn, grapeseed, and rice bran oils.
While they are widely used for their shelf-stability and low cost, the processes to extract and refine seed oils expose them to heat, light, and chemical treatments that result in the loss of nutrients and the formation of harmful compounds. This combination makes seed oils a significant contributor to chronic inflammation and oxidative stress.
What the Science Says
Omega-6 Fatty Acids and Inflammation: While omega-6 fatty acids are essential for health, an imbalanced intake—especially when omega-6 significantly outweighs omega-3 fatty acids—may promote inflammation. This imbalance has been associated with conditions such as cardiovascular disease and metabolic disorders.¹
Processing and Oxidation: The industrial extraction and refining processes of seed oils often involve high heat and chemical treatments, which can lead to both the formation of harmful compounds and the loss of beneficial nutrients. These processes may increase the susceptibility of oils to oxidation, leading to oxidative stress once we consume them.²
Heart Disease: In 2013, researchers published data on the Sydney Diet-Heart Study. They divided participants into two groups. Each group ate the same amount of fat and oil but the difference was that the experimental group’s fats and oils came from seed oils like margarine and safflower oil. Researchers followed these groups for the next seven years. The results? The experimental group that ate the seed oils had a rate of death 62% higher compared to the control group that ate less seed oil. This means that consuming seed oils has a higher likelihood of causing death than physical inactivity, heavy drinking, and excessive sugar consumption.³
Practical Tips To Avoid Seed Oils
Limit Processed Foods: Reduce your consumption of packaged and processed items that commonly contain seed oils.
Read Labels: Avoid products listing seed oils such as soybean oil, canola oil, or sunflower oil in the ingredients.
Choose Safer Cooking Oils: Opt for extra virgin olive oil, avocado oil, or coconut oil as healthier alternatives. Throw out your vegetable oils.
Avoid Restaurant Fried Foods: Request food be cooked in butter or olive oil, or limit fried items altogether when dining out.
Increase Omega-3 Intake: Balance your omega-6 consumption by eating more omega-3-rich foods like fish, walnuts, and flaxseeds, or consider a high-quality fish oil supplement.
Test Your Ratio: Use an at-home kit or consult your doctor to evaluate your omega-6 to omega-3 balance.
Cook at Home: Preparing meals at home gives you control over the oils used, reducing your exposure to harmful seed oils.
Find alternatives: The dangers of seed oils are gaining attention, and fortunately, many brands are stepping up to offer healthier alternatives. Avoiding "The Hateful Eight" can still be tricky, especially with condiments, which often sneak in seed oils. Thankfully, brands like Primal Kitchen provide a range of high-quality, seed-oil-free options, including salad dressings, cooking oils, ketchup, and more.
Live well,
Brian
For a deeper dive and full resources, check out this article: The Hidden Health Effects Of Seed Oils: What You Need To Know.
References
Innes, J. K., & Calder, P. C. (2018). Omega-6 fatty acids and inflammation. Prostaglandins, Leukotrienes and Essential Fatty Acids, 132, 41–48.
Calder, P. C. (2020). Dietary fatty acids and inflammation: Focus on the n-6 series. International Journal of Molecular Sciences, 24(5), 4567.
Ramsden, C. E., Zamora, D., Leelarthaepin, B., Majchrzak-Hong, S. F., Faurot, K. R., Suchindran, C. M., Ringel, A., & Hibbeln, J. R. (2013). Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: Evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis. BMJ, 346, e8707.