When patients seek nutritional advice, this handy guide to cooking oil can help

By Anastasia Climan, RDN, CD-N | Fact-checked by Barbara Bekiesz
Published March 12, 2024

Key Takeaways

  • Dietary fats have become a polarizing topic among the general public, and many are turning to their healthcare provider for advice that considers the latest research.

  • Replacing saturated fats with unsaturated fats is still highly recommended; seed oils have been proven to have beneficial properties, but these are mitigated with cooking and processing.

  • One oil stands the test of time: Decades of research still stresses the healthfulness of extra virgin olive oil.

Nutritional science is ever-evolving, making it tough to keep up with patients’ latest fads and beliefs. Social media only adds fuel to this fire. Now, a simple task like choosing the right cooking oil can leave patients feeling paralyzed in the grocery store.

In a world of low-carb diets, veganism, and everything in between, dietary fats have become a polarizing topic.

Here, we’ll decode the latest on fats for cooking so you can feel confident advising your patients.

An ongoing saga: Saturated fats

Saturated fat has long been considered an enemy of heart health, with the American Heart Association recommending intake should be limited to 6% of a person’s diet.[] However, some mixed opinions have left people questioning the merits of such strict restrictions, particularly if the saturated fat comes from natural sources like butter and coconuts. 

Individual variability in cholesterol homeostasis and genetic cardiovascular risks warrant more tailored saturated fat guidelines, particularly when considering other dietary factors, like fiber intake.

For now, medical consensus generally still favors replacing solid cooking fats with unsaturated options. But the health implications of different plant oils can vary widely.

How seed oils became controversial

The unsaturated fats in seed oils earned them a health halo that’s recently come under scrutiny. In their natural state, seed oils are a rich source of beneficial compounds.

Grapeseed oil, for example, contains vitamin E, linoleic acid, phytosterols, and phenolic compounds like catechins, and provides antioxidant, anti-inflammatory, and anticancer effects.[]

In addition, the consumption of flaxseed oil has been demonstrated to reduce systolic blood pressure in multiple randomized controlled trials.[] Unfortunately, it’s not well-suited for cooking.

Public health organizations commonly recommend rapeseed oil (canola oil) as a superior cooking oil practically on par with olive oil due to its negligible saturated fat. Although research generally favors canola oil, some conflicting observations prevent researchers from drawing a strong conclusion on its health impacts.[]

Once a health-fan favorite, the reputation of seed oils has been tarnished by social media gurus calling seed oils toxic and advising for complete elimination from the diet.

While extreme views on nutrition should always be taken with a grain of salt, there may be some merit to these emerging concerns.

The seed oils typically found in Western diets are highly refined and stripped of precious antioxidants before they’re added to processed foods. As a result, cutting back on ingredients like corn and soybean oil usually means avoiding unhealthy snacks and treats. Additionally, seeds oils are naturally high in omega-6 fatty acids, which tend to be overrepresented in modern diets.[] 

It’s also worth noting that some trans fats are produced when cooking with seed oils, particularly when stir frying at high temps.[] Which oils are best for which cooking methods may depend on their smoke point.[] Sunflower oil has a high smoke point, making it suitable for high-heat cooking like searing, browning, and deep frying. In fact, it has a higher smoke point than canola, grapeseed, and peanut oil. 

Hemp, pumpkin, and sesame oils also have beneficial properties, but are delicate and better saved for the last few minutes of cooking to prevent heat damage. Oils such as flaxseed, walnut, and wheat germ should be reserved for use in dressings, dips, and marinades, rather than for cooking.

Why olive oil is still the gold standard

The Mediterranean diet is frequently named as the best diet for longevity and good health. One hallmark characteristic of the diet is the inclusion of olive oil.

Studies show that virgin olive oil protects LDL particles against oxidative damage due to its hydroxytyrosol content.[] The polyphenols in olive oil consistently demonstrate cardiovascular benefits in clinical trials, even when used for cooking.

While it may sound like old news, encouraging patients to cook with olive oil is sound nutritional advice.

Avocado oil is another plant-based option with a similar thermal stability to that of olive oil, and it has a higher phytosterol content. However, it has lower levels of vitamin E, slightly more saturated fat, and a lower omega-3 to omega-6 ratio than olive oil.[] Certain nut oils, like almond and hazelnut oil, are also very low in saturated fat and stand up well in high temperatures. However, their distinct taste isn’t suitable for every culinary creation.

What this means for you

Explaining the nutritional differences between unrefined seed oils and those found in processed foods can help patients make healthier choices. Those already consuming a good balance of omega-3 fatty acids, and using unprocessed seed oils with high smoke points (like sunflower), are less likely to experience potential proinflammatory effects. Virgin olive oil still reigns supreme for cooking, with avocado and some nut oils following close behind.

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