For some reason, seed oils have become heavily demonized by many people in the health and fitness industry. Some of the leading “experts” recommend avoiding seed oils as one of the most important nutritional guidelines to follow. Seed oils are attacked by several different factions of the diet industry including the carnivore crowd, the organic crowd, and those advocating for a more natural diet.
"They’re a byproduct of industrial manufacturing processes and are not meant for human consumption."
"Eating seed oils will cause a ton of inflammation, which will contribute to you developing diseases like diabetes and cardiovascular disease."
Essentially, seed oils will undoubtedly kill you...
At least, that’s what the anti-seed oil crowd wants you to think.
They claim that seed oils cause inflammation, contribute to obesity, and increase the risk of chronic diseases. However, this perspective is not based on robust scientific backing. In reality, the nutritional value and health impact of seed oils can vary greatly depending on the type of oil, the processing method, and the overall diet and lifestyle of an individual.
In this article, we are going to dive head-first into the topic of seed oils and review scientific data to see whether any of these claims are substantiated. By the end of the article, you should have a better understanding of what seed oils are, how they impact our health, and make informed decisions about whether or not you’d like to include them in your diet.
What are seed oils?
First, let’s discuss what exactly these notorious seed oils are. By definition, seed oils are fats extracted from the seeds of plants. Unlike oils pressed from fruits like olives or coconuts, seed oils come from – you guessed it – seeds! These include popular varieties like sunflower, canola (derived from rapeseed), soybean, corn, and grapeseed oils.
Each has its own unique flavor profile, nutritional makeup, and are popular in cooking and food preparation. The reason they are popular is largely due to their desirable culinary properties, such as a high smoke point, which makes them ideal for high-heat cooking methods like frying, and their ability to blend well with other flavors without overpowering dishes. Contrary to what many “influencers” suggest, the reason they’re present in many foods is not because the food industry is conspiring to make you sick.
Why do people say seed oils are “unhealthy?”
There are two major reasons why people like to hate seed oils:
The production methods used
And the fact that they’re high in omega-6 fatty acids
Let’s discuss how these oils are made.
Producing seed oils typically involves a series of steps that transform seeds into clear oils we see on store shelves. The process usually starts with cleaning and grinding the seeds, followed by pressing or solvent extraction to release the oil. Hexane is the most commonly used solvent to extract seed oils, but isopropyl alcohol and ethanol can also be used.
Now, this is where people often have issues. Solvent extraction sounds like a chemistry experiment that doesn’t belong in your food.
But that’s not true at all.
In reality, solvent extraction is a standard and highly regulated process in the food industry, used to efficiently and safely extract oils. Solvent extraction methods are used because they are highly efficient at separating the oil from the seed material. Fatty acids, which make up a large part of these oils, are soluble in solvents like hexane, allowing for a more complete and effective extraction of the oil. The solvents used, like hexane, are later removed from the extracted oil through a series of steps to ensure that the final product is safe for consumption.
In other words, none of the solvents are present in the final product. Arguing that seed oils are unhealthy due to their processing methods is equivalent to saying that your drinking water is unhealthy because it's purified through filtration and chemical treatments.
Solvent extraction methods are widely accepted and monitored by food safety authorities globally.
With regard to their omega-6 content causing inflammation and disease, well, that simply doesn’t seem to be true at all. However, let’s take a deeper dive into the available scientific literature to discuss what the research actually shows.
What does the clinical research show?
When it comes to the health impacts of seed oils, particularly concerning chronic inflammation and disease risk, we need to rely on high-quality scientific evidence. Randomized clinical trials (RCTs) and meta-analyses provide the most reliable form of evidence to understand these impacts. Let’s explore the findings of some of the latest research on the topic of seed oil consumption and health-related outcomes.
Spoiler alert: the vast majority of the research DOES NOT SUPPORT the idea that seed oils are bad for you.
For example, in a comprehensive systematic review and meta-analysis, researchers delved into the health impacts of canola oil, specifically its effects on lipid profiles, glycemic indices, inflammation, and blood pressure, in comparison with other commonly consumed edible oils. The analysis, which synthesized data from 42 articles, revealed that canola oil, a plant-based oil, has a significant effect on improving cardiovascular risk factors. Notably, the study found that canola oil consumption led to a significant reduction in total cholesterol and low-density lipoprotein (LDL) cholesterol, among other lipid markers, when compared to other edible oils. These findings highlight the potential of canola oil as a healthier alternative in dietary fat choices .
Similar findings exist with regard to inflammatory biomarkers as well.
Linoleic acid, a primary omega-6 polyunsaturated fatty acid commonly found in many seed oils, has been a subject of scientific interest due to its potential impact on inflammation. A systematic review and meta-analysis of randomized controlled trials was conducted to investigate how increasing dietary intake of linoleic acid affects blood concentrations of inflammatory markers. The comprehensive analysis, which included 30 randomized controlled trials with a total of 1377 subjects, explored various inflammatory markers, such as cytokines, acute phase reactants, and adhesion molecules. These markers are crucial indicators of inflammation and are often linked to chronic diseases. The study concluded that a higher intake of dietary linoleic acid does not significantly affect these blood inflammatory markers, showing that concerns about its pro-inflammatory effects is overstated .
That being said, the truth is that these topics are complex. It’s not accurate to say that all data point to seed oils as being extremely health-promoting. For example, a systematic review and meta-analysis, including data from randomized controlled trials, that investigated the health outcomes of replacing saturated fats with vegetable oils rich in linoleic acid, showed that replacing saturated fats has no discernible evidence of a decrease in mortality from coronary heart disease or in all-cause mortality as a result of this dietary substitution .
Overall, the latest clinical research, particularly from randomized controlled trials and meta-analyses, does not support the blanket assertion that seed oils are bad for your health. Some of the conflicting data simply show that there are other variables, like total caloric intake, as well as genetic variables, that influence someone’s predisposition to disease development as well as sensitivity to the health-promoting/deterring effects of specific fatty acids. At the very least, we can say that seed oils are likely no worse than other types of fats, and to say that they cause inflammation and disease is simply inaccurate. It's crucial to view these findings within the broader context of overall dietary patterns and lifestyle factors.
1. Amiri, Mojgan et al. “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 : NMCD vol. 30,12 (2020): 2133-2145. doi:10.1016/j.numecd.2020.06.007
2. Su, Hang et al. “Dietary linoleic acid intake and blood inflammatory markers: a systematic review and meta-analysis of randomized controlled trials.” Food & function vol. 8,9 (2017): 3091-3103. doi:10.1039/c7fo00433h
3. Hamley, Steven. “The effect of replacing saturated fat with mostly n-6 polyunsaturated fat on coronary heart disease: a meta-analysis of randomised controlled trials.” Nutrition journal vol. 16,1 30. 19 May. 2017, doi:10.1186/s12937-017-0254-5