Why? Because the vast majority of them are derived from GMO crops, riddled with neurotoxic pesticides, oxidized, rancid, and loaded with high estrogen and omega-6 content.
A single tablespoon of soybean oil, for example, contains the estrogen equivalent of a birth control pill! That’s a lot of estrogen. In men, this drops sperm counts, plummets testosterone levels, and triggers overall endocrine dysfunction. In women, it can drive PCOS and feed endocrine-related cancers such as breast and ovarian cancer. Not good.
And the worst part? These oils are hidden in almost everything. The average American now gets about 30% of their daily calories from these rancid, toxic oils. They’re in almost all packaged foods, making it critical to read the ingredients list.
Want to stay safe? Avoid seed oils and opt for reliable, healthy animal fats like grass-fed tallow instead.
1. More Estrogen in a Tablespoon of Soybean Oil than in a Birth Control Pill
Soybean oil is extremely high in phytoestrogens — plant-derived compounds that mimic estrogen in the body. In concentrated amounts, like those in ultra-refined cooking oils, these estrogenic compounds disrupt hormonal balance. Some researchers have compared the estrogenic load from small amounts of soybean oil to that of pharmaceutical birth control, especially when consumed daily over time.
2. The Cancer Connection Is Becoming Clear
Population studies and lab research have drawn disturbing links between high omega-6 polyunsaturated fatty acid (PUFA) intake and the progression of aggressive cancers. Tumors fed a high-PUFA diet show increased growth rates, and excessive omega-6 from seed oils has been shown to drive inflammation, oxidative stress, and cell mutation — the perfect storm for cancer development.
3. Originally Designed as Machine Lubricant
Seed oils like cottonseed, canola, and soybean oil weren’t invented for cooking. In the 19th century, they were marketed as cheap industrial lubricants and lamp oils. It wasn’t until aggressive marketing campaigns by Procter & Gamble that these industrial fats were repurposed and sold as “heart healthy” cooking oils.
4. Aldehydes: The Same Toxins Found in Cigarette Smoke and Car Exhaust
When heated, seed oils produce toxic aldehydes — the same class of compounds found in cigarette smoke and diesel exhaust. These aldehydes damage DNA, accelerate aging, and cause oxidative stress throughout the body. The irony is that many people switched from butter to seed oils to “be healthy,” only to expose themselves to toxins every time they fry an egg.
5. When “Experts” Say Seed Oils Are Healthy…
Mainstream nutrition authorities continue to push seed oils as “heart healthy” because they lower LDL cholesterol on paper. But lowering LDL by replacing stable animal fats with unstable, oxidation-prone seed oils is like replacing the roof of your house with tissue paper — it might look fine until the storm hits.
6. High in Estrogen and Omega-6
Seed oils aren’t just estrogenic — they’re also loaded with omega-6 fatty acids. While omega-6 is essential in small amounts, the modern diet has skewed the omega-6 to omega-3 ratio to an inflammatory 20:1 or worse. This imbalance drives systemic inflammation, hormonal disruption, and metabolic disease.
7. Black, Gunky, and Tar-Like Before Refining
Before they’re bleached, deodorized, and deodorized again, seed oils are thick, black, and gunky. The industrial refining process strips away the sludge-like impurities, but it also requires high heat, solvents like hexane, and chemical bleaching agents — leaving behind a product far from “natural.”
8. Choose Wisely
Put grass-fed tallow next to seed oil, and you’ll see the difference in both color and stability. Tallow is rich in stable saturated and monounsaturated fats, resistant to oxidation, and naturally nutrient-dense. Seed oils, on the other hand, are fragile, prone to rancidity, and come with a long list of metabolic and hormonal risks. The choice should be obvious.
Closing Thoughts
Seed oils are a modern invention, never consumed in human history until the last century. Their industrial origins, chemical processing, hormonal disruption, and cancer-promoting tendencies make them one of the most damaging additions to the modern diet. Replacing them with stable, nutrient-rich animal fats like tallow and butter is one of the simplest and most impactful steps you can take for your health.
References
- Almeida, C., et al. “Phytoestrogens and Their Health Effects.” Nutrition and Health, vol. 32, no. 1, 2022, pp. 3–17. https://doi.org/10.1177/02601060211061228.
- Cook, M. E., et al. “Dietary n-6 Polyunsaturated Fatty Acids and Cancer Risk.” Journal of Nutrition, vol. 124, no. 8, 1994, pp. 1358–1363. https://doi.org/10.1093/jn/124.8.1358.
- Mozaffarian, Dariush, et al. “History of Modern Vegetable Oils.” The American Journal of Clinical Nutrition, vol. 100, no. suppl_1, 2014, pp. 919S–926S. https://doi.org/10.3945/ajcn.114.083998.
- Zhong, Y., et al. “Formation of Toxic Aldehydes in Heated Oils.” Food Chemistry, vol. 230, 2017, pp. 349–356. https://doi.org/10.1016/j.foodchem.2017.03.035.
- Lopes, F. C. C., et al. “Polyunsaturated Fatty Acids and Inflammation.” Prostaglandins, Leukotrienes and Essential Fatty Acids, vol. 159, 2020, 102142. https://doi.org/10.1016/j.plefa.2020.102142.
- Gómez, C., et al. “Refining of Edible Oils: A Critical Appraisal.” European Journal of Lipid Science and Technology, vol. 121, no. 11, 2019, 1900193. https://doi.org/10.1002/ejlt.201900193.