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Cooking Oil Smoke Points: Are We Asking the Right Questions?

03/06/2014 09:19 BST | Updated 02/08/2014 10:59 BST

Imagine yourself perusing your supermarket's cooking oils, overwhelmed by the seemingly endless choices. A recurrent term catches your eye—high smoke point. Not one to trust product labels, you reach for your phone, eventually landing on the Cleveland Clinic's website. "Heating oil above its smoke point," you read, "produces toxic fumes and harmful free radicals."

The message is clear—avoid dangerous molecules by choosing high smoke point oils—but the logic is flawed. High smoke point oils are advertised as healthy and safe, but when it comes to choosing cooking oils, are there more pertinent questions we should be asking?

Opinions vary as to which oils have the highest smoke points, but refined oils always have higher smoke points than their unrefined counterparts. The following refined oils are commonly marketed as high smoke point cooking oils: avocado, grapeseed, canola, coconut, corn, peanut, safflower, sesame, soybean, and sunflower.

Refined gentlemen are elegant, cultured, and indeed respectable. But what about refined oils? Do they command the same respect? The oil refinement process, which involves hexane solvents, high heat (180 to 220°C), bleaching, and deodorizing, raises numerous health concerns, particularly those associated with hexane residues, trans fats, and damage to heat-sensitive polyunsaturated fatty acids (PUFAs).

There are three types of fatty acids—saturated, monounsaturated, and polyunsaturated. Most fatty foods contain all three, but are dominant in one. Butter and coconut, for example, are primarily saturated. Olive oil and avocados are primarily monounsaturated. Seed oils, including corn, grapeseed, soybean, and sunflower oils, are primarily PUFAs. When exposed to heat, PUFAs become chemically unstable, promoting oxidative deterioration and free radical chain reactions.

In other words, the oil refinement process, despite increasing an oil's smoke point, critically denatures its PUFAs. Further oxidative damage occurs during cooking, even when oils are heated below their smoke points. Free radical chain reactions ensue, which eventually promote systemic inflammation and various degenerative diseases.

As you probably known, some scientists are working towards a unified field theory of physics, a theory to explain everything. But did you know medicine has its own unified field theory? Increasingly, scientists are recognizing inflammation as the common thread connecting almost all diseases. In 2003, for example, the American Heart Association and Centers for Disease Control issued a landmark statement that heart disease essentially stems from inflammation. Would you be interested to know that some, but not all, PUFAs are significant sources of inflammation?

PUFAs, of which there are two varieties—omega-6 and omega-3—are known as essential fatty acids. We require them from food, but only in very small amounts. And whereas omega-3 prevents inflammation, excessive omega-6 is increasingly recognized as a primary inflammatory driver of heart disease, cancer, and other degenerative diseases.

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Returning to our aforementioned high smoke point oils, we see that many are high in omega-6. The smoke point issue therefore raises many critical questions. Should we be eating omega-6-rich foods? Should we eating PUFAs that have been heated? Is high-heat cooking necessary?

Fat is an essential macronutrient and at 9 calories per gram, compared to 4 each for protein and carbs, the stakes are high. We should choose the healthiest sources, predominantly saturated and monounsaturated, and consume them raw or minimally heated.

For low-heat cooking, I use healthy sources of heat-stable saturated fat, primarily butter and virgin coconut oil. Saturate fat, of course, was once believed to promote heart disease, but modern science increasingly shows it doesn't. On the other hand, replacing saturated fat with omega-6 actually increases heart disease mortality.

I regularly enjoy steamed foods with liberal amounts of healthy fat applied post-cooking. My primary fat sources include coconut, butter, olive oil, avocados, and full-fat fermented dairy (yogurt and kefir). In my opinion, smoke point proclamations give the impression that refined PUFAs are safe and omega-6-rich diets are healthy. The science suggests otherwise.

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Christopher James Clark is the author of the critically acclaimed book, Nutritional Grail: Ancestral Wisdom, Breakthrough Science, and the Dawning Nutritional Renaissance