17% Drop in Death Risk Starts with One Small Oil Change in Your Kitchen

Written by

Louise W Lu, PhD, MPH, BMLS

Reviewed by

Alexandra V Goldberg, Registered Dietitian

Ever stood in a supermarket aisle, staring at shelves of cooking oils and feeling completely lost?

On one side: extra virgin olive oil, avocado oil, flaxseed oil. On the other: familiar staples like canola, soybean, even butter and coconut oil. Which are truly healthy? Which are overrated—or even harmful? And is that everyday spoonful of oil helping or hurting your health?

In this first post of our Cooking Oil Series, we unpack the real science behind fats—starting with saturated vs. unsaturated oils—and help you choose what actually belongs in your kitchen.

01｜Saturated vs. Unsaturated Fat: Which One Lowers Your Risk of Death?

We’ve all heard that some fats are “good” and others are “bad.” But can switching the type of fat you cook with—like using olive oil instead of lard or butter—really help you live longer?

A major Harvard study says yes. After tracking over 220,000 people for more than 30 years, researchers found that those who ate more plant-based oils like olive, canola, or soybean oil had a 16% lower risk of early death. Those who ate more saturated fat—such as butter, lard, or beef fat—had a 15% higher risk.

Even small changes helped: swapping just 10 grams of saturated fat a day (about a tablespoon of butter or lard) for plant oil lowered the risk of dying early by 17%.

So what’s the difference?

Saturated fat raises “bad” cholesterol (LDL) and increases inflammation, both linked to heart disease and cancer.
Unsaturated fat, found in plant oils, does the opposite—it supports heart health and may help your metabolism work better.

In short:
Saturated fat clogs. Plant oils protect.

And the best part? This isn’t a strict diet. It’s a simple swap you can make in your kitchen—one that could add years to your life.

02｜How Is Cooking Oil Made — And What Are You Really Eating?

Cooking oil may seem simple, but how it's made can tell you a lot about its quality, nutrition, and what you're really putting into your body.

Most oils you see in supermarkets—like soybean, canola, corn, and sunflower oil—are industrial seed oils, extracted using a multi-step process. It starts with crushing the seeds at high pressure and heat. Then, to get as much oil as possible, manufacturers often add a chemical solvent called hexane—a petroleum-based liquid that pulls out every last drop of oil from the plant material.

Once the oil is extracted, it’s not ready for your kitchen just yet. It goes through refining, which typically includes:

• Bleaching: to remove color and pigments
• Deodorizing: to eliminate smells
• Degumming and neutralizing: to remove free fatty acids, waxes, and phospholipids

The result is what’s known as RBD oil—short for Refined, Bleached, and Deodorized. This is the kind of oil found in most clear plastic bottles on grocery store shelves.

On the other end of the spectrum are cold-pressed oils, like extra virgin olive oil or unrefined avocado oil. These oils are extracted mechanically, without heat or solvents. This allows them to retain more of their natural antioxidants, color, and flavor—and often, a higher price tag.

But the difference isn’t just about nutrients. It’s about how the oil was made, what was lost or added along the way, and how much processing was needed to make it look and taste “neutral.”

That processing isn’t always a bad thing. In fact, RBD oils are specifically treated to remove impurities that could cause the oil to go rancid, taste bitter, or smoke too easily during cooking. The refining process also helps standardize the oil’s stability and shelf life, making it more practical for commercial food production and everyday high-heat cooking at home.

03｜Smoke Point, Oxidation, and Polar Compounds: Why We Use Refined Oils

Why are refined oils—like canola, sunflower, rice bran, and camellia oil—so common in everyday cooking?

The answer lies in chemistry. Refined oils are more stable under heat. They have higher smoke points, resist oxidation, and generate fewer harmful polar compounds than many unrefined oils. That’s why they’re preferred not only in restaurants but also in home kitchens—for stir-frying, roasting, baking, and searing.

These three factors—smoke point, oxidation resistance, and toxic breakdown products—are key to choosing a cooking oil. Here’s what they mean:

What is smoke point?

The smoke point is the temperature where oil starts breaking down and smoking. At this point, it releases acrolein (an eye- and lung-irritating compound) and begins to lose flavor and nutrition.

Oils with higher smoke points are better for high-heat cooking.

What is oxidation?

Oxidation happens when oils react with air, heat, or light. It breaks down fatty acids, produces off-flavors, and creates free radicals and aldehydes—compounds linked to inflammation and chronic disease.

Refined oils oxidize more slowly because unstable compounds have been removed during processing.

What are polar compounds?

When oils are overheated or reused repeatedly, they form polar compounds: altered molecules like peroxides, aldehydes, and polymers. These degrade flavor and may be harmful to health if consumed frequently.

So how do popular oils actually perform? Let’s look at real data—including modern oils like Perilla Seed Oil and Camellia Oil, which are gaining attention for their nutrition profiles but require care in cooking.

Note: Oxidation stability depends on the oil’s fatty acid profile. Oils high in monounsaturated fats (MUFA) are generally more heat-stable than those rich in polyunsaturated fats (PUFA).

As you can see, refined oils with high MUFA and low PUFA tend to withstand high heat best—like rice bran, high-oleic sunflower, and refined avocado oil.

Meanwhile, delicate oils like Perilla or Flaxseed Oil are best for cold dishes only. Heating them can destroy nutrients and generate harmful byproducts.

Smart oil choices don’t just make your food taste better—they help protect your long-term health too.

04｜LOLU Nutritionist’s Guide: Which Oil to Use, and When

There’s no such thing as the “perfect oil.” But there is a right oil for the right job.

From a nutritionist’s perspective, the best cooking oil depends on how you use it, how often you use it, and what kind of stability it offers during heat exposure.

Here’s how we recommend choosing oil in your kitchen:

For high-heat cooking (≥200°C)

Use refined, heat-stable oils with high smoke points and low oxidation risk:

• Refined avocado oil
• Rice bran oil
• High-oleic sunflower or canola oil
• Refined peanut oil
• Refined camellia oil

These oils are ideal for stir-frying, oven roasting, searing, or deep-frying. They remain stable, don’t oxidize easily, and have a clean, neutral flavor.

For medium or low heat (≤180°C)

Use mildly refined oils with moderate heat tolerance and flavor character:

• Light olive oil
• Refined sesame oil
• Ghee (clarified butter)
• Refined coconut oil (in moderation)
• Unrefined camellia oil

These are great for gentle sautéing, baking, or finishing sauces. While not as antioxidant-rich as cold-pressed oils, they perform well at moderate heat.

For cold use or finishing touches

Use cold-pressed or delicate oils to preserve nutrients and flavor complexity:

• Extra virgin olive oil
• Flaxseed oil
• Perilla seed oil
• Walnut oil
• Unrefined sesame oil
• Unrefined avocado oil

These oils are best used for salad dressings, dips, drizzle-over applications, or post-cooking enrichment. They are not suitable for heating due to their low smoke points and oxidation sensitivity.

The LOLU rule of thumb?
Don’t stick to one oil. Rotate based on the dish, cooking method, and your nutritional goals.

This way, you benefit from a diverse range of fatty acids and antioxidants—while minimizing the risks of overusing any one type of fat.

Let your oil work for you, not against you.

Authors:

Louise W Lu

Registered Nutritionist (NZ Reg. 82021301), PhD of Nutrition Science, Honorary Academic at the University of Auckland. Louise blends clinical research with public health to help people eat better and live stronger.

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Alexandra V Goldberg

Registered Dietitian (NZ Reg. 20-02273) and expert in nutrition, medicinal chemistry, and skincare. Alexandra helps clients reach their health goals with science-backed strategies in post-op recovery, feeding tolerance, and weight management.

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