Since 2018, the health effects of consuming certain processed vegetable oils, often referred to as seed oils, have been a subject of debate, fueled by misinformation spread through popular and social media channels. This trend gained momentum in 2020, particularly after podcaster Joe Rogan's interview with Paul Saladino, a proponent of the carnivore diet.
Seed oils are extracted from the seeds of plants through industrial processes, setting them apart from oils derived from the pulp or fruit. These oils are characterized by their high content of polyunsaturated fatty acids (PUFAs). Critics often highlight a group of oils they call the "hateful eight," including canola, corn, cottonseed, soy, sunflower, safflower, grapeseed, and rice bran oils, which emerged with industrialization in the early twentieth century.
The Rise of Seed Oils
A prime example of seed oil's introduction to the American market is cottonseed oil. Procter & Gamble developed and marketed it as Crisco in 1911. The extracted oil underwent refinement and partial hydrogenation, transforming it into a solid at room temperature, mimicking natural lard. It was then canned under nitrogen gas.
Understanding Fatty Acid Composition
Oils derived from seeds typically have the lowest percentage of saturated fat and vary significantly in their omega-3, omega-6, and omega-9 content. Sunflower, corn, and soybean oils contain a higher proportion of omega-6 fatty acids compared to oils from sources like fish, walnuts, flaxseed, and rapeseed (canola). Notably, omega-6 fatty acids are becoming an increasingly significant component of the fat intake in American diets.
Concerns and Controversies Surrounding Seed Oils
Opponents of seed oils argue that linoleic acid, an essential fatty acid abundant in oils like safflower and sunflower, elevates the risk of chronic diseases such as cardiovascular disease, cancer, and systemic inflammation. However, this notion is not substantiated by recent clinical trials or long-term epidemiological studies. On the contrary, research indicates that higher levels of linoleic acid in circulation and tissues are associated with a lower risk of major cardiovascular events.
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A 2025 review of human outcome data concluded that linoleic acid from seed oils does not increase chronic disease risk. It's worth noting that opposition to seed oils has sometimes been linked to certain political viewpoints.
Examining the Claims Against Seed Oils
One argument against seed oils centers on oxidized LDL (low-density lipoprotein) as a predictor of cardiovascular disease. Critics suggest that seed oils contribute to the oxidation of LDL, thereby increasing heart disease risk. However, comprehensive research demonstrates that the total number of circulating ApoB-containing lipoproteins, including all LDL particles (oxidized or not), is the most accurate predictor of cardiovascular disease. Higher ApoB levels are generally associated with a higher risk of heart disease.
Some studies indicate that oxidized LDL in circulation may be less likely to penetrate the artery wall and contribute to plaque buildup (atherosclerosis). Furthermore, seed oils have been shown to potentially lower ApoB levels, improve insulin sensitivity and blood glucose control, reduce visceral fat, and even improve inflammation and blood pressure.
When evaluating specific foods, it's crucial to prioritize research that examines overall health outcomes rather than focusing solely on individual mechanisms. Nutrients and foods like seed oils interact with our physiology in complex ways, some of which are still not fully understood.
A 2019 meta-analysis published in Circulation, involving tens of thousands of participants tracked for up to 32 years, found that individuals with higher levels of linoleic acid in their blood and fat stores had a lower risk of major cardiovascular events.
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Addressing Misinformation and Bias
Some critics point to studies like the Minnesota Coronary Experiment as evidence against seed oils. However, that study has limitations, including a high dropout rate and questions about potential trans fat contamination in the vegetable oil group.
It's important to consider meta-analyses that combine the results of multiple trials. For instance, a 2020 Cochrane review, encompassing over 10 trials and more than 53,000 participants, found that diets lower in saturated fats and higher in unsaturated fats from plant oils were associated with a significantly reduced risk of cardiovascular events.
Nutrition science is complex, and single studies can have limitations in study design, adherence, and conclusions.
The Role of Seed Oils in a Balanced Diet
It's not necessary to actively incorporate seed oils into one's diet. Alternatives like olive oil are perfectly acceptable. The key takeaway is that seed oils are not inherently harmful as some portray them to be. A balanced, evidence-based approach to healthy eating is crucial.
Seed Oils and the Carnivore Diet: A Point of Contention
The carnivore diet, which emphasizes animal products, raises questions about the suitability of seed oils. While some proponents strictly adhere to animal-based foods, others may consider incorporating certain plant-based oils.
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Avocado Oil: A Closer Look
Avocado oil, derived from the pulp of the avocado fruit, is distinct from seed oils. It's rich in monounsaturated fatty acids (MUFAs), particularly oleic acid, which is known to promote cardiovascular health, improve cholesterol levels, and reduce inflammation. Additionally, avocado oil contains vitamin E, phytosterols, and carotenoids like lutein, which benefit skin and eye health.
With its neutral flavor and high smoke point (480°F to 520°F for refined versions), avocado oil is versatile for frying, roasting, grilling, and sautéing. Its mild, buttery taste also makes it suitable for salad dressings, dips, and marinades.
Seed Oils vs. Fruit Oils
Seed oils tend to be high in polyunsaturated fatty acids (PUFAs), potentially more inflammatory, and less stable. In contrast, fruit oils are primarily monounsaturated or saturated, more stable, and nutrient-rich.
How Avocado Oil Is Made
Cold-pressed (unrefined) avocado oil is produced by mechanically pressing fresh avocado flesh at low temperatures, preserving its natural green color, aroma, and antioxidants. Refined avocado oil undergoes filtration, heating, and sometimes bleaching or deodorizing, resulting in a lighter color and milder flavor.
While refined avocado oil offers a higher smoke point, cold-pressed oil retains more vitamins and phytonutrients. However, there is a risk of adulteration, where some commercial avocado oils are diluted with cheaper oils like soybean or canola.
Nutritional Profile of Avocado Oil
Avocado oil is almost entirely fat, providing concentrated calories without protein or carbohydrates. Each tablespoon (14g) contains approximately:
- Calories: 120kcal
- Total fat: 14g
- Saturated fat: 2g
- Monounsaturated fat (oleic acid): 10g
- Polyunsaturated fat: 2g
- Protein: 0g
- Carbohydrates: ~0g
Avocado oil also contains vitamin E, lutein, and phytosterols.
Health Benefits and Risks of Avocado Oil
Avocado oil offers several potential health benefits:
- Heart health: Oleic acid lowers LDL cholesterol and supports cardiovascular function.
- Anti-inflammatory: Antioxidants reduce oxidative stress.
- Skin and hair: Vitamin E improves skin elasticity and protects against sun damage.
- Nutrient absorption: Enhances the absorption of fat-soluble vitamins (A, D, E, K).
Potential risks include adulteration and higher price compared to other oils.
Avocado Oil and the Carnivore Diet: A Matter of Principle
While avocado oil is primarily fat and low in carbohydrates, it's technically not allowed on a strict zero-carb carnivore diet because it's plant-based. Some argue that consuming any plant oil can disrupt the diet, which aims to rely solely on animal products.
Additionally, avocado oil may cause minor digestive upset for those fully adapted to a zero-carb diet. Animal-based fats like tallow or butter are considered more carnivore-friendly.
Choosing and Storing Avocado Oil
When selecting avocado oil, opt for 100% pure, extra virgin, or cold-pressed labels. Choose brands with third-party purity testing and oils packaged in dark glass bottles. Store avocado oil in a cool, dark place and use it within 6-12 months after opening.
Avocado Oil vs. Canola Oil
Avocado oil differs significantly from canola oil in terms of source, processing, fat composition, and cooking stability. Avocado oil comes from fruit flesh, while canola oil is extracted from rapeseeds. Canola oil is almost always refined with solvents, whereas avocado oil can be consumed unrefined. Avocado oil is higher in monounsaturated fats and lower in PUFAs, while canola contains more PUFAs. Avocado oil is also more stable at high temperatures.
Addressing the "Seed Oil Conspiracy": Separating Fact from Fiction
The idea that seed oils are a hidden ingredient causing obesity and chronic diseases has gained traction, often blaming them for the health issues traditionally attributed to bacon cheeseburgers, carbohydrates, and sugar. This narrative often labels seed oils as "linoleic acid," "omega-6 fatty acids," and "polyunsaturated fatty acids (PUFAs)."
Some nutritionists refer to common seed oils as the "Hateful Eight," including soybean, corn, canola (rapeseed), safflower, sunflower, cottonseed, grape seed, and rice bran oil, suggesting that these fats were not historically part of the human diet.
Challenging the Historical Claims
The assertion that humans did not consume beans and grains until recently is used to argue that seed oils are unnatural. Proponents suggest that our ancestors were primarily hunter-gatherers who consumed mostly meat and fruit, with fat sources coming from animals and fatty fruits like olives, avocados, and coconuts.
Understanding Fat Types and Oxidation
The argument often distinguishes between saturated, monounsaturated, and polyunsaturated fats. Saturated fats, primarily from animal fats and coconut oil, are solid at room temperature because they are "saturated" with hydrogen, making them less prone to oxidation. Monounsaturated and polyunsaturated fats, found in fatty fruits and seeds, respectively, have areas lacking hydrogen bonds, allowing oxygen atoms to attach and potentially causing oxidation, which is linked to inflammation and disease.
The Introduction of Seed Oils and Its Impact
The narrative highlights the introduction of large amounts of polyunsaturated fats into the human diet around a century ago, starting with Crisco, which chemically processed cottonseed oil for popular consumption. Before World War I, cottonseed oil was used to lubricate machinery, but it was later advertised as a "heart-healthy" alternative to traditional fats like tallow, lard, and butter.
Seed oils were also introduced into livestock feed, particularly for monogastric animals like chickens and pigs, which store these oils in their fat. This means that when we consume bacon or chicken skin, we are also consuming the stored seed oils. Cows, being polygastric animals, can convert some of the fats they eat into healthy saturated fat.
The Ideal Amount of PUFA Consumption
The ideal amount of PUFA consumption is suggested to be less than 10 grams per day. Even with a healthy diet avoiding seed oils, some PUFA intake is unavoidable from sources like red meat and eggs.
Debunking Misinformation
The claim that consuming PUFA reduces cholesterol and that high LDL cholesterol is linked to heart disease is presented as misinformation benefiting the agriculture industry and the medical establishment. It is argued that lowering LDL cholesterol does not protect against heart disease and may even increase the risk.
While omega-3 fats (like fish oil) are also polyunsaturated, they are considered less harmful than omega-6 poly fats from seed oils. The focus is placed on minimizing seed oil intake rather than balancing omega-3 and omega-6 ratios.
The Detoxification Process
Researchers suggest that the half-life of seed oils in the human body is 680 days, taking 4-7 years to completely remove stored seed oils from the body. Given the alleged link between seed oils and diseases like obesity, heart disease, diabetes, and cancer, the recommendation is to avoid seed oils as much as possible.
Practical Strategies for Avoiding Seed Oils
At home, it's recommended to replace "vegetable" oils with beef tallow, butter, high-quality olive oil, and coconut oil. Avoiding chicken and pork fat, while still consuming the protein, is also advised. Additionally, it's important to avoid beans, nuts, and seeds, as they are sources of seed oils.
Eating at restaurants poses a greater challenge, as many restaurants use seed oils due to their low cost. Fried food, sautéed food, salad dressings, and sauces are often high in seed oils. The suggestion is to opt for beef burgers (without the bun or mayo) and steak, which are less likely to contain added oils.
The "French Paradox" and Seed Oils
The "French paradox" is mentioned, attributing the lower rates of obesity and Western diseases in France to the historical use of animal fats in cooking. However, it's noted that many French restaurants in the US use canola oil, requiring consumers to inquire about the type of oil used.
Potential Benefits of Eliminating Seed Oils
The elimination of seed oils may lead to several benefits, including improved carbohydrate tolerance, reduced cravings, and decreased sunburn susceptibility.
A Focus on Ancestral Diets
The narrative emphasizes the importance of consuming foods that align with ancestral diets, primarily animal foods and fruits. Fruits are defined broadly to include sweet fruits, as well as vegetables like zucchini, cucumber, avocado, olives, and coconut. Root vegetables like carrots and sweet potatoes are also mentioned as potentially beneficial.
The Dangers of Seed-Derived Foods
All foods derived from seeds, including nuts, grains, and beans, are portrayed as damaging to the human body due to the presence of seed oils and other plant toxins. These toxins, such as gluten, lectins, oxalates, phytates, phytoestrogens, phenols, saponins, and tannins, are said to damage the intestinal lining and overall health.
Olive Oil and Avocado Oil: Considerations
While olive oil and avocado oil are monounsaturated fats and don't contain PUFA, they still have one bend, making them susceptible to oxidation. It is recommended to use cold-pressed ("extra virgin") oils stored in dark containers. Concerns about adulteration with seed oils are also raised.