Seed oils have been nothing but a hot topic in the media these days. In this blog, I dive into the research surrounding a few of the most common health claims surrounding seed oils to see if they are true or not. Like with most social media buzz around a certain food or nutrition claim, it tends to thrive on fear mongering with no research-based evidence to back it up which can spread nutrition misinformation like wildfire. So, let’s clear the air and see what the science says.
Article is available in ASL, scroll down to see video at the bottom of the page.
Defining Seed oils
It’s important we start off by defining seeds oils. Seed oils are oils extracted from the seeds of various plants, vegetables, seeds or nuts and typically named after the source it came from.
Examples of the most common seed oils:
- Canola
- Corn
- Cottonseed
- Soybean
- Sunflower
- Safflower
- Peanut
- Flaxseed
Saturated v. Unsaturated Fats
Before we get into the research, let’s review some nutrition basics regarding fat. If you are familiar with the different types of fat and their effect on human physiology, feel free to skip down to the first topic!
Fat is an essential macronutrient our body needs to support brain function, regulate hormones, provide some energy and help maintain healthy skin and hair. Not all fats are created equal though. Saturated fatty acids (SFA) are fats solid at room temperature and found primarily in animal products like red meat, cheese, butter, lard, and coconut oil. Numerous scientific studies1 have shown that a high consumption of saturated fats in the diet can raise levels of LDL cholesterol, or “unhealthy” cholesterol which is a key risk factor for developing cardiovascular disease, including heart attack and stroke.
Unsaturated fats, such as monounsaturated fatty acid (MFA) and polyunsaturated fatty acid (PUFA) are fats that are liquid at room temperature. However, they are also found in whole foods like avocados, nuts and tofu. They pose many healthful benefits in the body such as improving blood cholesterol, ease inflammation, stabilizing heart rhythms and lowering the risk of heart disease when consumed in moderation. That is always why they’ve coined the name “heart-healthy fats” 2,4.
- Seed oils high in monounsaturated (MUFA) fats are found in safflower, canola, sesame and sunflower8
- Seed oils high in polyunsaturated fats (PUFA) grapeseed, corn, cottonseed and soybean oil8
Now that we reviewed the basics regarding fats, it’s time to break this topic down further. Bear with me as this will come together in the following sections 😊
Nutrition claim: “Omega 6 is bad for you”
Omega-3 and Omega-6 are types of polyunsaturated fats (PUFA) which we just learned above, are heart healthy fats that we should include in our diet. In fact, they are essential! Essential fatty acids mean our bodies cannot make it on its own and it needs to be sourced through food.
- Omega-3 fatty acids are found in fatty fish like salon and trout, ground flaxseeds, and walnuts
- Well-known for their anti-inflammatory properties and benefits for brain and heart health
- Omega 6 fatty acids are found in seed oils, nuts and poultry.
- They play a vital role in brain function, skin health and help reduce harmful cholesterol and increase healthy cholesterol in the body.
Each seed oil has different ratios of monounsaturated fatty acid (MFA), polyunsaturated fatty acid (PUFA) and saturated fatty acids (SFA), but all of them are going to be higher in MFA and PUFA than SFA5 which makes them a source of healthy fats in the diet. Evidence from 15 clinical trials supports the notion that replacing saturated fat with polyunsaturated fat in the diet is associated with a lower risk of cardiovascular disease9. As well as a meta-analysis showing the replacement of SFA with PUFA reduced cardiovascular risk by 29%”3.
A Simple Replacement
Furthermore, another meta-analysis of randomized control trials examined both direct and indirect evidence regarding the effects of 13 oils and solid fats including safflower, sunflower, canola, hempseed, flaxseed, corn, olive, soybean, palm and coconut oils and beef, fat, lard and butter. In short, the results showed that replacing dietary sources of higher saturated fat content such as butter or lard and replacing them with oils rich in PUFA and MUFA such as safflower, sunflower, canola, olive, flaxseed, corn or soybean oil can lead to a reduced risk of atherosclerosis4 (the buildup of plaque in artery walls which is a major cause of heart disease).
According to the current research, claiming “Omega-6 is bad for us” is not accurate. It is an essential fatty acid and can actually aid in reducing harmful cholesterol in the body.
Nutrition Claim “Seed oil cause inflammation due to an Unbalanced Omega 3 to Omega 6 Ratio”
If omega-6 PUFA is essential and has heart healthy properties, why are seed oils getting so much negative attention? Well, in the body omega-6 has the potential to be turned into a longer chain fatty acid called arachidonic acid. Arachidonic acid can have pro-inflammatory and blood clotting properties in the body. So, the buzz around media is claiming that eating more Omega-6 than Omega-3 can cause a “imbalanced ratio” which produces inflammation in the body.
When this was studied in humans (not just a test tube), researchers found that “the body converts very little omega-6 into arachidonic acid even when omega-6 is abundant in the diet, meaning eating more omega-6’s does not cause inflammation” 6. Furthermore, it was found that eating more omega-6 fats either reduced markers of inflammation or left them unchanged6.
While it’s true that Americans consume more omega-6 than omega-3 fats largely due to the prevalence of seed oils present in ultra-processed foods, the concern isn’t just seed oils themselves, but rather what comes along in these foods: excess added sugars, unhealthy fats, and high sodium that can negatively impact health. Based on the current research, instead of eliminating omega-6’s or seed oils, the focus should be on ensuring sufficient intake of omega-3 intake to support cardiovascular health, as both are important. Incorporating seed oils in less processed forms can support overall health without the downsides of some ultra-processed foods.
Nutrition Claim: “Seed oil are produced with lots of chemicals which make them toxic”
There are a few processing techniques when it comes to extracting oil from a seed:
Cold pressed (Expeller-Pressed): The oil is extracted using mechanical pressure without heat or chemicals. With this process, most of the oil is kept inside the seed, therefore this is not the most efficient process to get the maximum amount of oil. Cold-pressed oils can be a great option, but they tend to be more expensive than refined oils due to their specialized extraction process and shorter shelf life.
Refined: The oil undergoes processing with heat and sometimes chemicals to remove impurities and increase shelf life.
Solvent-Extracted: A chemical solvent (typically hexane) is used to extract the maximum amount of oil from seeds, following by refining. This also helps remove undesirable minor components. This is the most efficient method for obtaining all the oil out of a seed and is usually the most common way seed oil is produced7 (unless otherwise stated “cold pressed” on the label).
Hexane is hazardous in gas-form but in food processing, for seed oil extraction, its used as a liquid solvent and then is removed from the product through evaporation. It’s important to note that the FDA does not set a monitor or regulate for hexane in finished seed oils. Good Manufacture Practices do require that manufacturers validate their processes to ensure that residues are minimized according to toxicological data and risk assessments. Organizations such as the National Oilseed Processors Association (NOPA) provide guidelines that enforce the notion that processing methods used, effectively reduce hexane levels to negligible amounts and safe for consumption10,11.
The European Food Safety Authority (EFSA) has established a maximum residue limit for hexane in their food products. This proactive regulation sets an example for food safety and hopefully in the future the US can follow in EFSA’s footsteps by creating similar standards ensuring even more consistent safety for consumers when it comes to hexane residue in oils.
Final thoughts…
Like with most things when it comes to nutrition, balance and moderation is key and this also applies to seed oils in your diet. Nutrition science is a young science, and it is constantly evolving. As new studies emerge, our understanding of seed oils and their effects on health may expand, but for now, focusing on an overall balanced diet is a good approach.
The 2020-2025 Dietary Guidelines for Americans (DGA) recommend consuming a healthy dietary pattern through the lifespan. One of their main focuses emphasizes the importance of a healthy dietary pattern as a whole, rather than looking at it as individual nutrients12. Meaning, eating a variety of nutrient dense foods – fruits, vegetables, whole-grains, lean proteins, and healthy fats regularly is more important than obsessing over one specific “superfood”. The DGA recommends limiting saturated fat to less than 10% calories per day. If someone is following a 2,000-calorie intake, that would be 20g of fat coming from saturated fat each day12.
Also, the American Heart Association recommends replacing saturated and trans-fat with monounsaturated (MUFA) and polyunsaturated (PUFA) fats. More specifically, they recommend 5-10% of daily calories coming from omega-6 fats. For example, if you are following a 2,000-calorie diet, that would be 11-22 g/ day. This could look like:
- 1 oz. walnuts – 10.9 g
- 1 tablespoon sunflower oil for cooking or in a homemade salad dressing – 3 g
- 1 tablespoon peanut butter (pair with banana or use in a smoothie)– 2 g
With most of these foods you are getting other nutritional benefits such as fiber, protein and phytonutrients.
Are there any other questions you want answered regarding seed oils? Drop it in the comments below!
If you are an individual who is supported by Jay Nolan Community Services and interested in working with the organizations internal Registered Dietitian Nutritionist, or have a blog topic suggestion, please send an email to nutritioncorner@jaynolan.org.
Medical Advice Disclaimer: The information provided on this blog is for informational and educational purposes only. No material provided in this blog, including images and graphics, is intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health care provider before making any dietary changes or starting a new health care regimen. Do not neglect professional advice because of what you may have read in this blog.
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References:
1.Siri-Tarino, P. W., Sun, Q., Hu, F. B., & Krauss, R. M. (2010). Saturated fatty acids and risk of coronary heart disease: modulation by replacement nutrients. Current atherosclerosis reports, 12(6), 384–390. https://doi.org/10.1007/s11883-010-0131-6
2.Kris-Etherton, Penny M. “Monounsaturated Fatty Acids and Risk of Cardiovascular Disease.” Circulation, vol. 100, no. 11, Sept. 1999, pp. 1253–58. DOI.org (Crossref), https://doi.org/10.1161/01.CIR.100.11.1253.
3.Sacks FM, Lichtenstein AH, Wu JHY, Appel LJ, Creager MA, Kris-Etherton PM, et al. Dietary Fats and Cardiovascular Disease: A Presidential Advisory From the American Heart Association. Circulation. 2017;136(3):e1–23.
4.Chwingshackl L, Bogensberger B, Benčič A, Knüppel S, Boeing H, Hoffmann G. Effects of oils and solid fats on blood lipids: a systematic review and network meta-analysis. J Lipid Res. 2018;59(9):1771–82.
5.“WHAT DOES THE SCIENCE SAY ABOUT SEED OILS?” https://www.soyconnection.com/old-pages/resources/health-nutrition-newsletter/health-nutrition-newsletter-details/what-does-the-science-say-about-seed-oils
6.“No Need to Avoid Healthy Omega-6 Fats.” Harvard Health, 1 May 2009, https://www.health.harvard.edu/newsletter_article/no-need-to-avoid-healthy-omega-6-fats.
7.Prof. Sarah Berry, (podcast guest). (2024, September 12). Seed oils are not ‘evil’ – they could lower your risk of disease. In Science & Nutrition. ZOE.
8. FoodData Central. https://fdc.nal.usda.gov/.
9.Hooper L, Martin N, Jimoh OF, Kirk C, Foster E, Abdelhamid AS. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database of Systematic Reviews. 2020;5(5):CD011737.
10. NOPA – The Use of Hexane in Oilseed Processing. (n.d.). https://www.nopa.org/wp-content/uploads/2023/10/Hexane-Fact-Sheet-PUBLIC-FINAL.pdf
11. Food Chemical Safety | FDA
