The Dangers of Seed Oils and Trans Fats | AIRD™ Series #5

Seed oils and trans fats lurk in countless processed foods and even so-called “healthy” foods. But are these fats doing your body more harm than good?

For decades, outdated guidelines and powerful marketing has promoted seed oils, including canola, corn, sunflower, soy, grapeseed, rice bran, and cottonseed, as heart-healthy essentials. Thankfully, new science is prompting a serious rethink. Let’s uncover why these highly processed fats could be undermining your health—and which fats truly nourish your body.

This article is part of the Anti-Inflammatory Rainbow Diet™ (AIRD™) series—a practical, faith-based framework centered on whole, properly prepared foods that calm inflammation and help your body thrive as intended. The AIRD™ avoids modern inflammatory ingredients such as seed oils and trans fats, and emphasizes traditional, colorful, nutrient-rich foods rooted in God’s design for nourishment.

Want to learn more about AIRD™ and how it can transform your relationship with food? Dive deeper in God’s Prescription: A Faith-Based Plan to Shift Your Mindset and Reclaim Your Natural Health.

“It Wasn’t the Salsa…”

For years, I couldn’t figure out why I’d get a surge of phlegm almost every time I ate out. It was especially bad at Mexican restaurants. At first, I blamed the salsa. But it kept happening—even with other cuisines. Then one evening, my husband accidentally overheated oil in a dish at home. The smell instantly made me feel off, and I realized I was having that same reaction. That’s when it clicked: it wasn’t just the salsa. It was the chips, or more precisely, the oils they were fried in.

Over time, I noticed the reaction was even worse when the oil was overheated or reused—just like it often is in restaurants.

Digging deeper into seed oils, I soon realized my symptoms weren’t just a nuisance. My body was actually trying to protect me.

How Are Seed Oils Really Made?

Manufacturers make vegetable oils by extracting fats from either plants or plant seeds. When you spot oils like soybean, corn, canola, safflower, sunflower, grapeseed, rice bran, or cottonseed in an ingredient list, you’re almost always looking at refined seed oils—products of heavy industrial processing. Here’s how these modern oils make their way from seed to supermarket shelf:

Cold-Pressed Oils:

In contrast, producing cold-pressed oils—like extra-virgin olive oil or authentic avocado oil—involves much gentler methods. The seeds or fruits are pressed at low temperatures (usually below 120°F/49°C) and never exposed to chemical solvents. Production is typically smaller-scale, with traditional presses or modern hydraulic equipment, but rarely the high-pressure, high-speed machinery of a seed oil refinery.

This process preserves far more of the oil’s natural nutrients, color, and flavor.

For example, cold-pressed, extra-virgin olive oil:

• • Preserves dozens of plant-based antioxidants—including polyphenols and vitamins E and K—making it a nutrient-rich, anti-inflammatory fat choice.
  • Contains compounds with antioxidant, anti-inflammatory, and neuroprotective effects, such as oleuropein, oleocanthal, and hydroxytyrosol.
  • Is linked to reduced LDL cholesterol, improved blood pressure, and slower cognitive decline in populations with high olive oil intake.

Cold-pressed oils often appear cloudier or deeper in color, reflecting their retained nutrients and pigments. They’re usually packaged in dark glass bottles (not plastic), which helps protect the delicate fats from light and microplastics, and labeled “cold-pressed,” “extra-virgin,” or “unrefined.” The taste and aroma remind you of the real food they were pressed from.

Hydrogenated Oils (Trans Fats):

Hydrogenated and partially hydrogenated oils—better known as trans fats—are created when manufacturers take liquid vegetable oils and blast them with hydrogen to make them solid at room temperature. This process changes the natural fat structure and makes the oil behave differently in your body. Think of natural saturated fats as straight puzzle pieces that fit perfectly in your cells, while trans fats are twisted ones that jam the works.

Saturated fats (like those in butter or coconut oil) have all their chemical bonds “filled” with hydrogen. This makes them stable during cooking and safe for our cells to use.

Trans fats are now widely recognized as some of the most dangerous fats, strongly linked to an increased risk of heart disease, insulin resistance, and metabolic dysfunction. Because of this, the AIRD™ excludes them completely.

So, how did these highly processed, industrial oils go from factory floors to your dinner table? Let’s look at how seed oils infiltrated the modern diet…

How Did These Oils Invade Our Food Supply? A Brief History Lesson

It’s hard to imagine now, but just over a century ago, seed oils were virtually absent from our diets. So, how did these industrial oils become so deeply woven into modern eating?

Early 1900s: From Waste to Wonder

In the early 1900s, the booming cotton industry left behind a problem: excess cottonseed oil. Procter & Gamble turned this “waste” into profit by processing it into a white, shelf-stable fat called Crisco. Marketed as a modern alternative to lard and butter—and proudly promoted as “digestible,” as if that were a high nutritional standard—Crisco was a hit.

Hydrogenation: Making Shelf-Stable Profits

To further extend shelf life and appeal, manufacturers started hydrogenating liquid oils, turning them into solid trans fats (aka margarine and shortening). This process made storage and transport easy—great news for manufacturers, but not so good for our bodies.

World Wars and Government Guidance

Butter shortages during World War I gave margarine a marketing boost with government backing. Clever campaigns and nutrition “experts” claimed these new products were actually healthier.

The Demonization of Saturated Fat

Enter Ancel Keys: In the 1950s, his research blamed saturated fats (like butter and lard) for rising heart disease. Though his data was flawed and cherry-picked, the theory stuck. By the 1970s, government guidelines were urging Americans to avoid animal fats and embrace plant-based oils.

The Seed Oil Boom

Food manufacturers jumped on board, swapping out natural fats for cheap, industrial oils in everything from chips and salad dressings to granola bars and frozen meals. Today, it’s nearly impossible to avoid them: most packaged foods, even “healthy” ones, contain seed oils like soybean, canola, safflower, or sunflower oil.

A Modern Challenge

And good luck finding a restaurant that doesn’t use them! Most commercial kitchens rely on cheap seed oils—most often soybean oil—for frying, sautéing, and even salad dressings.

(Tip: The Seed Oil Scout app can help you locate eateries that avoid these oils.)

Unless you’re reading labels and making intentional choices, these oils end up in nearly every meal.

Wait! Aren’t Plant Oils Healthy?

The science around seed oils and heart disease can seem a bit mixed. Some studies suggest these oils are heart-healthy, but it’s important to look deeper and connect the dots.

Even minimally processed seed oils are very high in omega-6 fatty acids, which, when consumed excessively, can fuel chronic inflammation—a key factor in many chronic diseases, including heart disease.

Moreover, these oils are chemically unstable when heated, such as during frying, making them prone to oxidation that forms harmful byproducts. These byproducts include aldehydes and free radicals, both of which have been linked in studies to inflammation, cardiovascular disease, and even cancer. Their reactive nature can damage cells and DNA.

Humans evolved to consume omega-6 and omega-3 fatty acids in a ratio of about 1:1 to 4:1. Sadly, the ratio in the Western diet is highly imbalanced—often around 15:1 or even higher. Because omega-6 and omega-3 fats compete for the same enzymes in the body, too much omega-6 can block omega-3’s benefits. This imbalance shifts the body toward chronic inflammation, which is linked to heart disease, metabolic disorders, and many other chronic health conditions.

These industrial seed oils aren’t the ancestral fats our bodies evolved to handle. The AIRD™ focuses instead on biblical and ancestral fats: fats from naturally raised animals and cold-pressed oils derived from whole foods like olives, avocados, and coconuts.

Restoring Balance with Omega-3s

While most Western diets overload the body with omega-6 fatty acids, omega-3 fats—found in foods like wild-caught fish, flaxseeds, walnuts, and pasture-raised animal products—help counteract inflammation and support brain, heart, and immune health. Omega-3s have anti-inflammatory effects and help restore balance to your body’s fatty acid profile.

Restoring a healthier balance between omega-6 and omega-3 fatty acids is a key step in reducing chronic inflammation and lowering the risk of heart disease, diabetes, and other chronic illnesses.

That’s why AIRD™ encourages eating more foods rich in omega-3s—like fatty fish and grass-fed meats—while minimizing processed seed oils to bring your body back to its natural, health-supporting state.

Good Oils Gone Bad: How Even Healthy Fats Can Be Compromised

• • Improper storage: Cold-pressed oils like extra-virgin olive oil and unrefined avocado oil should be stored in a cool, dark place to retain their flavor and chemical stability. When exposed to heat, light, or air, these oils oxidize—drastically reducing their quality and health benefits.
  • Heat sensitivity of cold-pressed oils: These oils are delicate by design. Exposing them to high temperatures during cooking or processing can degrade antioxidants, alter their fatty acid structure, and create harmful byproducts. For optimal health benefits, use these oils raw or for low-heat cooking—and store them away from heat and light.
  • Avocado oil confusion: Unrefined avocado oil is a healthy, nutrient-rich fat. However, many brands on the market are highly refined or adulterated with cheaper oils like soybean or canola. Even authentic avocado oil can lose nutritional value and develop harmful compounds if exposed to high heat during cooking or manufacturing.
  • Olive oil adulteration: Some oils labeled “olive oil,” especially in restaurants or budget brands, are blended with soybean or other refined seed oils. These imitations lack the flavor, color, and benefits of authentic extra-virgin olive oil.

Recently, I was served what was supposed to be olive oil with my salad, but it lacked color and flavor. My husband agreed it wasn’t authentic olive oil, so I sent it back and simply used salt and pepper on my salad instead.

The Low-Fat Fallout: How Bad Science Made Us Fatter

After Ancel Keys blamed saturated fat for heart disease—using selective and flawed data—the government doubled down on low-fat recommendations. By the 1980s and 1990s, the low-fat and non-fat craze was in full swing. Fat became the new dietary villain, and processed snacks flooded supermarket shelves.

But something ironic happened: as fat was removed from foods, manufacturers replaced it with sugar, salt, and—most notably—inflammatory seed oils to boost flavor and extend shelf life.

The result? Rates of obesity, diabetes, and metabolic diseases skyrocketed.

God’s design didn’t include shelf-stable margarine or fake cheese spread. Instead, it gave us nourishing foods like olive oil, animal fats, and whole foods. The AIRD™ brings us back to that foundation.

Choosing healthy fats supports hormone balance, brain health, and reduces inflammation—all key pillars of AIRD™.

Practical Tips for Avoiding Seed Oils

• • Read ingredient lists: Even “natural” and organic products often contain seed oils. Watch for terms like “vegetable oil,” canola, grapeseed, sunflower, soybean, safflower, or cottonseed oil.
  • Be restaurant savvy: Most restaurants use cheap seed oils, especially soybean oil, for sautéing and frying. Don’t hesitate to ask what oils they use. If healthiest options aren’t available, choose grilled, steamed, or baked dishes.
  • Use the Seed Oil Scout app: This handy resource (available on iOS and Android) can help you find restaurants that avoid seed oils—but it’s always smart to double-check what fats they actually use.
  • Eat out less often: Cooking at home with whole-food ingredients gives you total control over your fats. Simple, scratch-cooked meals mean fewer surprises.

Better Fats for Your Kitchen

Choose these healthy fats:

For cooking:

• • • Grass-fed butter or ghee
    • Coconut oil
    • Duck fat, lard, or tallow from pastured animals
    • Unrefined avocado oil (best for low-to-medium heat only)
    • Extra virgin olive oil (best enjoyed raw or at low heat)

For baking or cold uses:

• • • Coconut oil or grass-fed butter
    • Avocado or olive oil

Learn how to save money by making your own ghee here.

The Bigger Picture: Why This Matters

For decades, dietary guidelines demonized saturated fats based largely on selective interpretations of data—most notably from Ancel Keys—shaping public policy in ways that modern science is now revisiting. In fact, the new USDA walks back its limits on saturated fat, acknowledging the complexity of fat’s role in health and recognizing that previous restrictions may have been misguided.

The Anti-Inflammatory Rainbow Diet™ invites you to return to the nourishing, traditional fats that sustained our ancestors and align with God’s design for wholesome nutrition. It’s time to move beyond industrial seed oils and artificial trans fats, reclaiming the healthy fats that truly fuel our bodies and support long-term wellness.

Ready to Dig Deeper?

Curious how to swap seed oils for better alternatives in your kitchen? Explore these delicious recipes to get started, and subscribe to receive more guidance, tips, and inspiration on living well.

• • Easy Beet Salad
  • Homemade Ghee
  • Salmon with Dill and Capers
  • Healthy Homemade Mayonnaise with or without eggs