Topic Guide

What Is Seed oils?

Seed oils is a subject covered in depth across 6 podcast episodes in our database. Below you'll find key concepts, expert insights, and the top episodes to listen to — all distilled from hours of conversation by leading experts.

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Key Concepts in Seed oils

Converging lines of evidence

This is a scientific framework emphasized by Dr. Norton for evaluating complex research questions. Instead of relying on a single study, it involves looking at the totality of evidence from various high-quality, rigorously controlled studies—including specific types like Mendelian randomization and statin trials—to build a robust understanding and confidence in conclusions.

Hexane extraction

This is the process by which most commercial seed oils are extracted from seeds using hexane, a non-polar solvent. The episode explains its use due to efficiency and low boiling point, and the subsequent steam removal, arguing that the conditions are not conducive to significant oil oxidation or harmful hexane residue.

Bioaccumulation (and lack thereof for hexane)

Bioaccumulation refers to the gradual build-up of substances in an organism. The episode discusses this concept to explain why trace amounts of hexane in seed oils are unlikely to cause harm, asserting that hexane does not bioaccumulate to appreciable levels and is efficiently cleared by the body.

Precautionary principle (in nutrition)

This is the idea that if there's a potential for harm from something, even without definitive proof, one should err on the side of caution and avoid it. Dr. Norton addresses this by saying that while individuals can choose to avoid seed oils, they should then actively replace saturated fats with other beneficial fats.

Energy toxicity issue

Dr. Norton uses this term to describe the fundamental problem driving disease in developed countries. It refers to the imbalance between high average calorie consumption (e.g., 3,500 calories/day in the U.S.) and extremely low physical activity (e.g., less than 20 minutes/day), leading to an excess of energy intake relative to expenditure.

First principles argument against seed oils

This concept posits that because humans did not evolve consuming seed oils in significant quantities, and now they constitute a substantial portion of modern caloric intake (10-15%), there is a fundamental reason to view them as potentially harmful. The episode challenges the simplicity of this argument by introducing biological and historical nuances.

What Experts Say About Seed oils

1.Industrial processing of seed oils, including heating, refining, and solvent extraction, is often cited as a primary concern, separate from the oils' linoleic acid content.
2.Hexane is used as a non-polar solvent for efficient oil extraction from seeds due to its ability to mix with oils and its relatively low boiling point of 69 degrees Celsius.
3.The steam and temperature used to evaporate hexane from crude oil are typically low and brief (minutes to an hour), generally insufficient to cause significant oxidation of the seed oils.
4.Residual hexane levels in commercially processed seed oils are extremely low, often non-detectable or ranging from 0.05 to 0.5 parts per million.
5.To experience even mild side effects from hexane ingestion, a person would need to consume an unrealistic 11,340 kg of oil at one time.
6.Hexane does not significantly bioaccumulate in the human body, which possesses mechanisms to convert it to innocuous compounds and clear it efficiently.