Soybean oil remains the most widely used cooking oil in the United States and is present in a large proportion of packaged and processed foods. Recent scientific work is now drawing attention to how this routinely consumed ingredient can promote obesity in animal models, offering important clues about its metabolic impact in humans.

The Experiment and What It Shows

Researchers fed one group of mice a soybean-oil–rich diet; they gained weight, accumulated fat, and showed metabolic changes. Another group with a slight genetic modification in a liver-fat–metabolism protein ate the same diet but did not gain weight.

This shows that the oil alone isn’t the only factor—how the body metabolizes it matters. Certain liver enzymes convert soybean-oil polyunsaturated fats into oxylipins, which can influence inflammation and fat storage.

The key takeaway: not all fats act the same in every body. Even common seed oils may cause metabolic issues in people with enzyme variations, inflammatory tendencies, or sensitivities (including those who react to seeds or spices).

Why Seed Oils Can Be Metabolically Harmful

Seed oils such as soybean, sunflower, safflower, corn, cottonseed, and canola share a common feature: they are rich in polyunsaturated fatty acids (PUFAs). These fats contain multiple double bonds, which makes them chemically unstable. When exposed to heat, oxygen, or even light, these bonds break down and generate reactive byproducts.

Oxylipins: How the Body Converts PUFAs Into Inflammatory Molecules

When the body metabolizes omega-6 PUFAs—particularly linoleic acid—it produces oxylipins. These compounds function as signaling molecules, but in excess, they contribute to inflammation, fat accumulation, and impaired metabolic regulation. This is exactly the mechanism highlighted in the mouse experiments: the animals that became obese produced more inflammatory oxylipins, while the genetically modified mice did not.

In human health, elevated oxylipins are associated with insulin resistance, non-alcoholic fatty liver disease, migraines, and immune dysregulation. For readers concerned with gut-health, chronic inflammation, and metabolic resilience, these pathways are highly relevant.

The Problem Intensifies During Cooking

PUFAs degrade rapidly during heating. When seed oils are used for sautéing or frying, they form aldehydes, lipid peroxides, and even small amounts of trans fats. These compounds place significant stress on the liver and contribute to oxidative damage. This is one reason why seed oils are repeatedly implicated in the rising prevalence of fatty liver disease in heavily urbanized regions such as China and Singapore.

The Refining Process Adds Further Burden

Most industrial seed oils undergo multiple stages of processing—extraction with petroleum-derived solvents such as hexane, bleaching, deodorizing, degumming, and high-temperature heating. These steps remove beneficial nutrients and pre-oxidize the fats, meaning the oil often reaches the consumer already damaged. Once used for cooking, oxidation escalates quickly.

Excess Omega-6 Intake Overwhelms the Liver

Linoleic acid (the primary omega-6 fat in seed oils) accumulates in cell membranes and promotes inflammatory pathways. High intake is now associated with disturbances in fat-burning genes, hormonal regulation, and mitochondrial function. This imbalance explains why populations with high seed-oil consumption often show higher rates of obesity and liver disease.

Why Ghee or Clarified Butter Do Not Behave the Same Way

Ghee is structurally different from seed oils. It is composed largely of saturated fats and short-chain fatty acids such as butyrate, which remain stable even at high temperatures. Saturated fats lack the vulnerable double bonds found in PUFAs, so they do not oxidize rapidly or form toxic byproducts during cooking.
Ghee also contains fat-soluble antioxidants that protect against oxidative stress. Its high smoke point makes it suitable for most forms of cooking, and its composition supports gut lining integrity and liver health. This stability sharply contrasts with the fragility of PUFA-rich seed oils.

Practical Guidance for Choosing Safer Oils

For high-heat cooking and frying, stability is the most important factor. Oils low in PUFAs are superior, while those high in PUFAs produce hazardous compounds when heated

Best oils for frying in the world as recommended by scientists

Frying requires high stability and low PUFA content.

BEST for frying (in order):

1. Ghee / Clarified Butter

• Smoke point: 250°C
• Highly stable saturated fat
• Zero oxidation
• Traditional in India + Middle East

3. Extra Virgin Coconut Oil

• Smoke point: 175–200°C
• 90% saturated fat
• Excellent for shallow fry
• Low oxidation

4. Avocado Oil (Unrefined)

• Smoke point: 190–200°C
• Low PUFA
• Contains monounsaturated fats

BUT NOTE: Many avocado oils are adulterated (studies show 70% of bottles are fake). Use only trusted brands.

Alright for frying (but not the best)

• Olive oil (light): stable at medium heat
• Rice bran oil: medium-PUFA, neutral flavor
• Mustard oil (if cold-pressed): good for Indian cooking but avoid deep-fry

❌ NEVER USE FOR FRYING (most unstable)

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

These create toxic aldehydes even at normal cooking temperatures.