Seed Oils and the Diary of a CEO Podcast

REALLY!!?!

Several clients this week have asked me about a recent Diary of a CEO episode that aired on January 27th. It seems like many of you listen to the podcast, so I wanted to address some of the controversies raised.

At the 1 hour 10-minute mark, the dietitian guest states that there is clearly no evidence that seed oils are unhealthy.

That’s just NOT TRUE.

There are numerous studies and reviews raising concerns about seed oils, particularly those high in omega-6 fatty acids (such as soybean, corn, canola, sunflower, and safflower oils). Here are some key points:

1. Omega-6 to Omega-3 Imbalance & Inflammation

  • Seed oils contain high amounts of linoleic acid, an omega-6 fatty acid that competes with omega-3s in the body.
  • Study: A 2018 review in Open Heart suggests that excessive omega-6 intake, combined with low omega-3 consumption, may promote chronic inflammation, which is linked to cardiovascular disease, obesity, and autoimmune disorders.
    • Source: Lands, W.E.M. (2018). “Historical perspectives on the impact of n-3 and n-6 nutrients on health.” Open Heart.

2. Oxidation & Toxic Byproducts

  • Seed oils are extracted at high temperatures using chemical solvents, leading to oxidation and the formation of harmful compounds like aldehydes.
  • Study: A 2017 paper in Redox Biology found that cooking with polyunsaturated-rich oils at high temperatures produces toxic aldehydes, which are linked to neurodegenerative diseases and cancer.
    • Source: Grootveld, M., et al. (2017). “Excessive consumption of omega-6 polyunsaturated fatty acids and oxidative stress.” Redox Biology.

3. Links to Obesity & Metabolic Dysfunction

  • Some researchers suggest that rising seed oil consumption correlates with increasing obesity rates.
  • Study: A 2020 study in Nutrients found that high dietary linoleic acid intake can promote fat storage and metabolic dysfunction in animal models.
    • Source: Tucker, C.J. (2020). “The role of linoleic acid in obesity and inflammation.” Nutrients.

4. The Heart Health Debate

  • While some studies suggest polyunsaturated fats lower LDL cholesterol, others question their long-term impact on heart health.
  • Study: The Sydney Diet Heart Study (2013) found that replacing saturated fats with linoleic acid-rich seed oils increased the risk of cardiovascular mortality.
    • Source: Ramsden, C.E., et al. (2013). “Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: The Sydney Diet Heart Study.” BMJ.

The Problem with Nutrition Research

In all transparency, the research on seed oils is mixed, which isn’t surprising. It’s extremely difficult to prove that any single food causes a disease, as there are too many variables.

Many nutritional studies rely on Food Frequency Questionnaires (FFQs), which depend on memory and self-reporting—both of which are unreliable.

Then there’s cherry-picking—highlighting convenient data while ignoring the rest. For example, some studies claim seed oils lower cholesterol compared to saturated fats. What’s often ignored is that in the Minnesota Coronary Experiment (1968–1973), seed oils lowered cholesterol but increased mortality. This data was hidden for decades and only resurfaced in 2016.

Finally, industry influence is real. Many nutrition studies are funded by companies that benefit from certain narratives.

It’s worth noting that Steven Bartlett was a company director for HUEL, a meal replacement brand that contains… you guessed it..  canola oil.

Professor Berry, the guest on the show, is associated with the British Nutrition Foundation, which has received funding from processed food companies that utilise seed oils in their products’’.

Food for thought.

My Take on Seed Oils

There’s no definitive proof that seed oils are harmful, but there’s also no conclusive proof that they’re safe. The research is mixed.

However, I personally choose to avoid them—not because of cherry-picked studies, but because of how they’re made:

  1. High-heat processing increases oil yield but also creates harmful byproducts.
  2. Hexane (a petroleum-based solvent) is used to extract the remaining oil.
  3. Refining & bleaching removes impurities and neutralizes odors with chemicals.
  4. Steam treatment removes strong smells and tastes but also destroys beneficial nutrients.
  5. Hydrogenation turns some oils into trans fats, which are known to be harmful.

To me, that’s enough reason to stick with natural fats like butter, tallow, coconut oil and ghee.