Traditional Fats vs Industrial Oils

The fats humans evolved on

Before the 20th century, the cooking fats available to humans were limited to what could be rendered, churned, or pressed with simple tools. Animal fats — tallow (beef), lard (pork), schmaltz (poultry), butter, and ghee — were staples in nearly every traditional cuisine. Plant-based fats came from fatty fruits and nuts: olive oil in the Mediterranean, coconut oil in the tropics, sesame oil in Asia. These fats share a common trait: they can be extracted mechanically, without chemical solvents, at low temperatures.

What changed

The industrial revolution brought a new category of fat into the food supply: oils extracted from seeds using chemical solvents. Soybean oil, corn oil, cottonseed oil, canola oil, sunflower oil, and safflower oil all require multi-step industrial processes — solvent extraction with hexane, degumming, bleaching, and deodorising — to produce a shelf-stable product. These oils did not exist in the human diet before the early 1900s. By 2000, soybean oil alone accounted for more than 7% of total caloric intake in the United States, according to USDA Economic Research Service data.

Soybean oil went from nonexistent in the human diet to more than 7% of total U.S. caloric intake in under a century.

What the new guidelines say about fat

The 2025-2030 U.S. Dietary Guidelines, published at RealFood.gov, take a notably different stance on fat than previous editions. Rather than warning Americans to limit fat intake, the guidelines state: "Healthy fats are a natural part of real foods such as meat, seafood, dairy, nuts, olives, and avocados. These fats support brain health, hormone function, and nutrient absorption." Full-fat dairy, eggs, nuts, seeds, olives, and avocados are all explicitly recommended. The guidelines define real food as being prepared "without added sugars, industrial oils, artificial flavors, or preservatives" — naming industrial oils as something to avoid.

RealFood.gov: 'Healthy fats are a natural part of real foods. These fats support brain health, hormone function, and nutrient absorption.'

Stability and oxidation

One of the key differences between traditional fats and seed oils is chemical stability. Saturated fats (butter, tallow, coconut oil) and monounsaturated fats (olive oil) are relatively stable when heated — their chemical bonds resist oxidation. Polyunsaturated fats, which dominate seed oils, are unstable. They oxidise readily when exposed to heat, light, and air, producing aldehydes and other reactive compounds. A 2012 study published in Food Chemistry by Grootveld et al. found that heating polyunsaturated-rich oils (sunflower, corn) produced significantly higher concentrations of toxic aldehyde compounds compared to olive oil, coconut oil, or butter.

The displacement effect

The rise of seed oils did not add new fats to the diet — it displaced the fats humans had eaten for millennia. Butter consumption in the U.S. dropped from 18 pounds per person per year in 1910 to under 4 pounds by 2000. Lard virtually disappeared from home kitchens. Tallow was removed from restaurant fryers (McDonald's switched from beef tallow to vegetable oil in 1990). These traditional fats were replaced almost entirely by soybean oil, canola oil, and other industrial seed oils — a shift driven by cost, shelf life, and decades of flawed dietary guidance that demonised saturated fat.

Choosing fats today

The principles are simple and now align with official U.S. guidance: cook with fats that humans have used for generations. Extra virgin olive oil for low-to-medium heat and dressings. Butter, ghee, tallow, or coconut oil for higher-heat cooking. Avoid oils that require chemical solvents to produce — if it needs hexane to extract, it is not a traditional food. Check ingredient labels for soybean oil, canola oil, sunflower oil, and "vegetable oil" (usually soybean). These are in virtually every packaged product, fast food item, and restaurant kitchen. Replacing them is the single most impactful change most people can make to their fat intake.