Are Seed Oils Bad for You? What Science Really Says!

If you should step into any health and wellness corner of the internet, you are likely to find a heated debate: are seed oils the silent killer lurking in our pantries, or are they a heart-healthy staple? From claims that they are “toxic” and “inflammatory” to endorsements from major health organizations, it’s easy to feel confused.

So, what’s the real story? This article will explore the controversy and the science behind common seed oils like canola, sunflower, and soybean oil. We’ll examine the arguments against them and compare them with what the scientific research actually says.  Let’s Discuss!

The Discussion

The discussion surrounding seed oils can feel overwhelming. On one hand, they are abundant in our modern diet, from processed foods to the kitchens of many restaurants. On the other hand, a growing number of voices are raising concerns about their potential impact on our health. So, what are seed oils, and what does the science actually say?

Seed oils are vegetable oils extracted from the seeds of various plants. Common examples include:

• Soybean oil
• Corn oil
• Canola oil (rapeseed oil)
• Sunflower oil
• Safflower oil
• Cottonseed oil
• Grapeseed oil
• Rice bran oil

These oils are widely used in cooking, food processing and are found in many packaged foods. They are often praised for being lower in saturated fat compared to some animal fats. Further, in some circles, the oils are often touted for their high polyunsaturated fatty acids (PUFAs). These include both omega-6 and omega-3 fatty acids, which are essential for our overall health (National Institutes of Health).

However, the processing methods used to extract these oils are a significant point of contention (Gaber et al. 2023; Dennett, 2023).  Many seed oils indeed undergo high-heat extraction, which often involves chemical solvents like hexane followed by processes like bleaching and deodorizing.  (Dennett, 2023).

Some have argued that the extreme methods used to extract the oils can lead to oxidation of the polyunsaturated fatty acids, which are delicate in nature [Wang et al. 2023 (Science Direct)].  The harsh methods have also been argued to reduce the oil’s nutritional value. Furthermore, the high omega-6 content in many common seed oils has raised concerns about an imbalance in the omega-6 to omega-3 ratio in our diets.

As such, research into the health effects of seed oils presents both a complex and often conflicting picture. As some studies have argued that high consumption of omega-6 to omega-3 fatty acids can promote inflammation (Patterson et al. 2012), while others have argued that moderate consumption, from properly processed seed oils, can be part of a healthy diet (DiNicolantonio JJ, O’Keefe, 2021).

In this article, we explore the common controversies and ways to find the balance, especially seeing that so many people, at this point, automatically consider them toxic based on varying research. But is this so?

Are Seed Oils Toxic?

• The case against seed oils
• What the science says
• Is Seed Oil really Bad?
• Some Useful Tips about Seed Oils

The Case Against Seed Oils – What are the Concerns?

The controversy surrounding seed oils isn’t unfounded; it stems from a few key concerns that are worth addressing head-on.  Here are the main ones.

1. The Omega-6 Overload:

This is perhaps the most common argument. Seed oils are high in omega-6 fatty acids or polyunsaturated fatty acids (PUFAs), specifically linoleic acid.  Linoleic acid, while it is generally promoted as being supportive to human health when consumed modestly, research contends that it is the excessive intake that can lead to the formation of ‘oxidized linoleic acid metabolites. 

Oxidized linoleic acid metabolites (OXLAMs) are bioactive derivatives of linoleic acid that have been cited in many pathological conditions (Patwardhan et al. 2010; Feldstein et al. 2010; Ku G et al. 1992, etc.).  As such, research contends that they can lead to chronic diseases such as cardiovascular disease, cancer and Alzheimer’s disease among others (Mercola and D’Adamo, 2023).

Further, research suggests that with the dramatic increase of linoleic acid in the human diet, this ignites a cause for grave concerns.  The most common source of polyunsaturated fatty acids (PUFAs) in the human diet today is vegetable and seed oils that contain linoleic acid (Ramsden et al. 2012). These oils can be found in many popular processed foods globally, which can increase one’s intake without even being aware.

2. Industrial Processing:

Both researchers and food advocates alike have raised concerns about the heavy industrial processing that seed oils undergo. The process can involve high heat, pressure, and chemical solvents like hexane to extract the maximum amount of oil from the seeds. It is argued that these harsh methods damage the fatty acids, which can create harmful compounds and depleting any potential nutrients (Gaber et al. 2023; Dennett, 2023).

3. Oxidation and Rancidity:

Because they are polyunsaturated, seed oils have multiple double bonds, making them chemically less stable than saturated fats (Ayala A et al. 2014).  As such, they are more susceptible to oxidation, especially when exposed to heat, light, or air (Ayala A et al. 2014).   The concern is that this oxidation can create rancid compounds in the bottle or, worse, inside our bodies, contributing to cellular damage.

Seed Oils – What the Science Says!

Now, let’s examine these claims under the microscope of scientific evidence.

1. The Omega-6 to Omega-3 Ratio Concern:

While an imbalance of the omega-6 to omega-3 ratio is a valid concern for overall health, eliminating all seed oils may not be the most practical or necessary solution.  Both omega-6 and Omega-3 are essential to our overall health; The key is the overconsumption of omega-6 in relation to omega-3.

This is because omega-6 fatty acids can be found in many of our foods, especially processed foods. As such, this creates an excess of omega-6 in relation to omega-3, particularly if one’s diet is not already a balanced, healthy one. 

In a research by Simopoulos in 2008, the researcher highlights how the change in the omega-6 to omega-3 ratio in Western diets, from an evolutionary ratio of approximately 1:1 to as high as 15:1 or 16.7:1, is a contributing factor to the development of many chronic diseases, including cardiovascular disease and inflammatory and autoimmune conditions.  The researcher also discussed how a lower ratio of omega-6 to omega-3 is more desirable (Simopoulos, 2008). So, less consumption of omega-6  fatty acids is the key!

However, an article from Stanford Medicine by Christopher Gardner, a Stanford researcher, provides a counter-perspective, arguing that the claims about seed oils being harmful are often misguided, particularly as it relates to omega-6 fatty acids overload.

His report presented evidence that unsaturated fats, including those in seed oils, can lower LDL (low-density lipoprotein) cholesterol and that the idea of omega-6 fatty acids being inherently pro-inflammatory is not fully supported by science. The report also pointed out that the negative health effects often attributed to seed oils are more likely due to their presence in ultra-processed foods. (Five things to know about seed oils and your health).

Nonetheless, there is no one takeaway from the impact of seed oil on our health, as it is a complex issue.   This argument was concurred by a systematic review by a group of researchers (Fornari et al. 2025).  The review suggests that certain seed oils may help to manage diabetes and dyslipidemia, though the effects are sometimes inconsistent. 

It also acknowledges the complexity of the research and the conflicting reports on the effects of these oils on health markers, suggesting that further research to clarify the role of seed oils in metabolic health is needed.

Therefore, the argument that omega-6 fatty acids are inherently pro-inflammatory remains a topic of debate in many scientific circles.  However, some research depicts otherwise. While some omega-6 fatty acid metabolites can be involved in inflammation,  a 2017 meta-analysis of thirty (30) randomized control trials found that increasing dietary intake of linoleic acid does not necessarily have a significant effect on the blood concentrations of inflammatory markers (Su H et al. 2017).

However,  the extent of dietary change of linoleic acid might have an impact on the effect of linoleic acid supplementation, particularly as it relates to C-reactive protein (CRP).  (Su H et al. 2017).  C-reactive protein (CRP) is a protein that is made by the liver. It is used as a marker for inflammation in the body.

2. On the Effects of High-Heat Procession

High-heat processing has always been a concern when it comes to our foods, and seed oils are certainly no exception. This is because these oils usually undergo tremendous processing, which not only reduces the nutritional value of the oils but can also lead to oxidation, which can cause serious health effects.

A study by Zhuang et al. (2022) found that high temperatures significantly increase the formation of lipid oxidation in products, which can potentially have harmful effects on human health. It notes that oils rich in polyunsaturated fatty acids (PUFAs), like soybean oil, are more susceptible to the formation of these harmful compounds when heated.

Additionally, a study by Szabo Z et al. (2022) indicated that repeated and prolonged heating of vegetable oils should be avoided, as it can change certain features of the oils, which can give rise to health consequences.  Further, the heating process changes the polyunsaturated fatty acids (PUFA) content of the oils and increases the saturated fatty acids (Multari S et al. 2019; Casal et al. 2010).  

It must be noted that these oils often use industrial solvents such as hexane (Dennett, 2023), which reports indicate can cause nerve damage (Wakelyn & Wan, 2003)

While older refining processes (e.g., partial hydrogenation) did create significant amounts of artificial trans fats, modern industrial methods have largely eliminated this issue. The World Health Organization (WHO) and other health bodies have successfully campaigned to ban these harmful fats from the food supply, leading to modern seed oils containing negligible amounts.

Additionally, improved manufacturing practices are stated to reduce the level of hexane to legibly amounts, which are not considered a health risk (European Food Safety Authority, et al. 2024; European Parliament, 2016).

Reports contend that agencies like the European Food Safety Authority (EFSA) conduct regular monitoring of the levels of contaminants in seed oil, including trans fats. They have also put regulations in place to control the heating process of the oils in the refining process, which is said to be even fewer than those found in milk and some related dairy products (European Food Safety Authority, 2004; 2024).

3.  Oxidation and Rancidity

The argument surrounding oxidation and rancidity boils down to how the oils were processed.

All fats can oxidize when exposed to high heat for extended periods. It’s crucial to use appropriate cooking methods for different types of oils based on their smoke points. Oils with higher smoke points, like refined sunflower, safflower, and avocado oil, are better suited for high-heat cooking. Storing oils in cool, dark places in airtight containers can also help prevent oxidation and rancidity.

So, are Seed oils really bad for you? – A matter of Context!

There is no simple answer to this question as the topic is a complex one. However, science does support its positive health effects, while denoting health consequences, particularly based on processing and over-consumption, especially via ultra-processed foods.

However, a more nuanced understanding is still needed. Most arguments suggest that the real problem isn’t a bottle of canola oil itself, but rather the modern dietary pattern that relies heavily on it within the context of highly processed, nutrient-poor foods. 

A diet of deep-fried fast food, packaged snacks, and sugary baked goods is unhealthy not because of the seed oil it contains, but because it’s a perfect storm of refined carbohydrates, unhealthy fats, and a lack of essential nutrients.

Therefore, the focus should be on cultivating a balanced approach when it comes to our health, such as consuming more whole foods and not necessarily vilifying one type of fat. Therefore, we should aim to prioritize healthy fats from a variety of sources, such as olive oil, avocado, nuts, seeds, and fatty fish (for omega-3s).

Ultimately, your health won’t be made or broken by a single bottle of oil in your kitchen. It’s the entire picture that counts, as indicated by the scientific research.

Some Useful Tips!

• Variety is key: Don’t rely exclusively on one type of oil. Incorporate a variety of healthy fats into your diet, including monounsaturated fats (olive oil, avocado oil), polyunsaturated fats (including omega-3s from fatty fish, flaxseeds, and some seed oils), and even saturated fats in moderation.
• Consider the processing: Opt for cold-pressed or expeller-pressed oils, when possible, especially for lower-heat applications like salad dressings.
• Use oils appropriately for cooking: Choose oils with higher smoke points for high-heat cooking methods.
• Focus on overall dietary balance: Prioritize a diet rich in whole, unprocessed foods, including plenty of fruits, vegetables, and omega-3-rich sources.
• Be wary of extreme claims: Nutrition information can be easily sensationalized online. Always look for evidence-based sources and consult with healthcare professionals or registered dietitians for personalized advice.

Therefore, instead of fearing all seed oils, focus on making informed choices about the types of fats you consume and how you use them. A balanced and varied diet is the cornerstone of good health.

Illustrative Summary

Here is an illustrative summary of the SEED OILS – Are they Good for YOU?

Let’s Sum Up!

The blanket statement that all seed oils are “toxic” is not supported by strong scientific evidence. According to some research, many seed oils, when consumed in moderation as part of a balanced diet and used appropriately in cooking, are not inherently harmful.

It’s also important to differentiate between various types of seed oils and their processing. Cold-pressed or expeller-pressed oils, which are extracted without high heat and chemical solvents, are often considered healthier options as they retain more of their natural antioxidants and are less likely to be oxidized.

Ultimately, navigating the seed oil debate requires a nuanced understanding. Therefore, one must be cautious in proclaiming blanket statements demonizing all seed oils.  Instead, the focus should be on the type of oil, its processing, and the overall balance of fats in one’s diet, as this seems more prudent.

Further, prioritizing whole, unprocessed foods, incorporating sources of omega-3 fatty acids like fatty fish and flaxseeds, and choosing minimally processed cooking oils like olive oil and avocado oil for higher-heat cooking might be a more health-conscious approach for many.

Nonetheless, as research evolves, it’s crucial to stay informed and critically evaluate the information available. Consulting with a healthcare professional or registered dietitian can provide personalized guidance based on your individual health needs and dietary patterns.

So, now that we have explored seed oils, do you have a better understanding of these oils? Do you use seed oils? If so, which one and for what purpose?  Share it Nuh!

You can read more about the fats in our food, as well as dietary patterns that use oils that are considered healthier and beneficial for our health. You can also watch the YouTube video about Seed oils, which provides a shortened version of this discussion.

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