How to Choose Cooking Oil

Remember when you could go to the grocery store to buy cooking oil and only had to decide between two or three types?

Today, the options are endless. In some respects, this is a good thing. Now that we know more about how oils affect our bodies and health, we can make smarter choices. At the same time, this remains a very complicated issue that still confounds experts in this area of science.

Here’s why.

When it comes to cooking oils, there are a couple important things to think about—their polyunsaturated and monounsaturated fat content, as well as omega-6 and omega-3 fatty acid content. Smoke point—the temperature at which the oil starts to break down—is another factor to keep in mind.

MUFA vs. PUFA

There are three main categories of dietary fats: saturated, monounsaturated, and polyunsaturated. Most vegetable-, seed-, and fruit-based oils are a combination of monounsaturated fat (MUFA) and polyunsaturated fat (PUFA).

Without getting too technical, the saturation of a fat is determined by how many hydrogen atoms vs. carbon atoms the molecule contains (as determined by the number of double bonds). Saturated fats (found in foods like butter and cheese) contain no double bonds. This enables the fat molecules to pack in close proximity to each other. This chemical characteristic also makes saturated fats harder to melt, so they are solids at room temperature.

Unsaturated fats contain more double bonds. These double bonds are disruptive to fat packing, and this chemical quality makes them a liquid at room temperature. The difference between polyunsaturated and monounsaturated fatty acids is the number of double bonds in the molecule, with monounsaturated fatty acids only having one and polyunsaturated fats having two or more.

Now, I’m a complete nerd, so I love this kind of stuff. But for those of you who don’t, I’ll tell you why this is so significant in a moment.

Within the polyunsaturated fatty acid (PUFA) family are two primary PUFAs—omega-6 and omega-3—and these are essential fatty acids in our diets.

OK, that’s enough biochemistry, what about cooking oils?

Most common cooking oils—soybean, corn, safflower, vegetable, cottonseed, peanut, sunflower—are rich sources of omega-6 fatty acids. As a nation, we are consuming more and more of these oils. In fact, our consumption of soybean oil alone has increased 1,000 times in the past 50 years. It is estimated that 8 percent of the total calories we eat each day come from soybean oil.

However, this overconsumption is problematic. As I’ve discussed extensively, omega-6 fatty acids shift our omega-6:omega-3 ratios and promote inflammatory responses in the body. Over time, this can increase risk of conditions such as Alzheimer’s and cardiovascular diseases, diabetes, and cancer.

Comparatively speaking, certain other oils, such as flaxseed, are greater in omega-3 fatty acids, which have been shown to help lower inflammation.

You would think this means that you should ditch your omega-6 oils and start cooking with omega-3 oils.

Not so fast…

One of the main problems with PUFAs is that they are chemically very unstable. Remember all those double bonds I mentioned earlier? Because of this chemical composition, PUFAs are very easily oxidized when exposed to high heat. This means they react with oxygen to form free radicals and harmful toxic byproducts that you certainly would not want to eat.

A recent study shows these oxidized PUFAs accumulate in plaques of the carotid arteries of heart disease patients. In fact, this potential public health disaster is well documented in the recent New York Times bestseller, The Big Fat Surprise by Nina Teicholz. PUFAs also tend to go rancid easily when exposed to light and air.

MUFAs, on the other hand, are much more resistant to heating. They are more stable and less likely to oxidize and go rancid, making them a safer, healthier option for cooking.

The “Smoking Gun”

The very last factor to keep in mind is smoke point. This is the temperature at which the oils break down and oxidize.

Oils utilized in frying, searing, baking, or roasting need to have a high smoke point. Many omega-6 oils, such as those mentioned earlier, fit the bill because they have particularly high smoke points.

So what makes these PUFAs so good for high heat cooking? Aren’t PUFAs unstable? Well, yes—but during the refining process, the extracting of the oils from the seed or vegetable also removes free fatty acids (as well as much of the taste, smell, color, and nutritional content). As oils become more and more refined—and free fatty acids are eliminated—the smoke point rises. So those omega-6–rich oils may have been altered to work well in the kitchen, but they’re still far from healthy.

Low smoke point oils, on the other hand, are either unrefined or only mildly refined. The first pressing (called “cold pressing”) extracts the oil using cool/warm water and a centrifuge. This allows the oil to retain much of its flavor, color, and nutritional content. Low smoke point oils are ideal for marinating or for low-smoke cooking techniques such as blanching, slow cooking, or steaming—but should not be used with high heats.

Your Best Options

I know this may be enough to make your head spin. But in a nutshell, here’s what you should know when choosing cooking oil: Look for high MUFA and low PUFA content to minimize oxidation, a favorable omega-6:omega-3 ratio to reduce your intake of pro-inflammatory omega-6s, and a high smoke point.

To help take the guesswork out of your next grocery trip, here are some of the best choices you can make based on the latest research.

Olive oil erroneously developed a reputation as a low smoke point oil with which you should not cook, but research is showing the opposite. In one study, researchers warmed two different extra virgin olive oils for 36 hours at 180°C (about 360°F). They found that, despite the heating, the oil “maintained most of its minor compounds, and therefore most of its nutritional properties.” While 360° is more along the lines of medium heat, olive oil’s high MUFA content (>75 percent) lends further support to the idea that you can confidently cook with it.

Canola oil is also called rapeseed oil. Rapeseed plants belong to the same genus of the crucifer family called Brassica, which includes turnips, Brussels sprouts, cabbage, kale, cauliflower, and broccoli. Canola oil has high MUFA concentrations and a high smoke point of 450°. It also contains a healthy omega-6:omega-3 ratio.

Macadamia oil contains up to 75 percent MUFA, has a favorable omega-6:omega-3 ratio, and a moderately high smoke point (about 400°).

Avocado oil is also a rich source of monounsaturated fats, with the added benefit of a high smoke point—520°.

Green tea seed oil is another great pick. Though not as easy to find at your average grocery store, you can easily buy it online. It has 80 percent MUFAs and a 485° smoke point.