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Ask the Diet Doctor: Cooking with Olive Oil

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Q: I’ve heard you shouldn’t cook in olive oil because it has a low smoke point. But a new study found that olive oil withstands the heat of a fryer or pan better than several seed oils. What’s the deal? Is the low smoke point just a myth? And are seed oils better off used for drizzling/dressing rather than cooking?

A: The smoke point is the temperature at which the oil begins to break down and discolor due to oxidation. Once you get too far past the smoke point of an oil, it's nutritional profile gets compromised, it starts to smell burned, and it imparts that burned taste to your food. Both the chemical structure of the oil and how it was processed impact the smoke point. As a general rule, oils that contain a lot of antioxidants (e.g. extra virgin olive oil) and oils with high amounts of polyunsaturated fats (e.g. flaxseed oil) have lower smoke points and are damaged more when exposed to high heat.

However, in the study you mention, published in Journal of Agricultural and Food Chemistry, researchers compared refined olive oil—not the peppery-tasting, antioxidant-loaded, first-pressed extra virgin olive oil we drizzle on salads—to corn, soybean and sunflower oil. (See which of these oils made the list of 10 Foods that Cause Inflammation.) Refined olive oil, which is chemically extracted from olives once the antioxidant-rich extra virgin oil is removed, is generally tasteless and essentially clear. Researchers both pan- and deep-fried potatoes in each of the oils, reusing the oils for 10 cooking sessions (as a means of trying to degrade the oils as much as possible). They found that refined olive oil, which is high in monounsaturated fats and thus has a high smoke point, held its chemical integrity best: It had the lowest formation of trans fats and was the most resistant to oxidation.

For no-cook preparations, I recommend extra virgin olive oil that has been pressed within the last 12-18 months (this ensures maximum freshness and antioxidants). For pan- or deep-frying, refined olive oil is a better choice than soybean, sunflower, or corn oil. Other good oil choices for daily cooking at higher temperatures are avocado oil, coconut oil, or canola oil, all of which have relatively high smoke points. (And whatever dish you create, store leftovers in one of these 12 Brilliant Eco-Friendly Eating Supplies.)

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