Are Olive Oil and Canola Oil Interchangeable?

To look at many cookbooks, you'd think olive oil and canola oil were identical twins separated at birth. Countless recipes call for "extra-virgin olive oil or canola oil," as if the two were interchangeable.

This implied equivalence is odd. Extra-virgin olive oil is cold-pressed from a fruit that has been cultivated for more than 7,000 years, with no refining beyond filtration. Canola oil is refined with heat, pressure, solvents, and bleach, and comes from the seed of a plant that's younger than the Rolling Stones.

The canola plant was conceived when demand for rapeseed oil plummeted in the late 1940s, and the Canadian rapeseed industry began seeking and creating new markets for its product. Since the Industrial Revolution, rapeseed oil has been an important component of lubricants for ships and steam engines, because unlike most oils it sticks to wet metal. During World War II the U.S. built a lot of ships, and so needed lots of rapeseed oil, but couldn't get it from traditional suppliers in Europe and Asia. The Canadian rapeseed industry, which had been relatively small, exploded to fill the gap, and played an important role in the allied naval effort, becoming rich and powerful in the process.

But rapeseed oil demand waned when the war ended, and thus began an intensive program to breed a rapeseed edible to humans. The Holy Grail was a strain with dramatically lower levels of erucic acid and glucosinolates, which are the main culprits behind rapeseed oil's foul flavor, and according to some research, toxic effects.

In 1978 the new plant was christened canola, for "CANadian Oil Low Acid." The "Low Acid" refers to erucic acid.

Canola is processed with heat, pressure, and often solvents like hexane. Even in cold-pressed "organic" canola, the refining steps include bleaching agents like clay, deodorization, and the removal of various gummy, oozy byproducts. In fact, many of these steps are similar to practices that people are worked up about over pink slime, including heated centrifugation and treatment with noxious chemicals. Care should be taken in sourcing olive oil, as well, as some that aren't extra virgin, cold pressed could also be altered by chemicals and heat. 

The refining process for canola oil can be seen in this YouTube video. The food and agriculture industries love canola because it grows well, yields more oil per acre than any other oilseed, and because there are so many ways to eat it. That bottle on your kitchen counter is only the beginning.

Canola oil is used in most processed salad dressings, often after being treated with anti-foaming agents. Canola oil is frequently hydrogenated for use in shortenings, fry oil mixes, and many processed foods. Canola oil hydrogenates much more readily than corn or soy oil -- a process that turns unsaturated fats into saturated fats and creates trans fats along the way. Canola hydrogenates so eagerly, in fact, that it happens inadvertently during the oil's steam-injection deodorization process. Because of this unintended hydrogenation, any refined canola oil is going to be partially hydrogenated. And if it's partially hydrogenated, it's going to contain trans fats. A study published in the Journal of Food Lipids shows that the trans-fat content of commercial, non-hydrogenated canola oil can be as high as 4.6 percent. Nonetheless, many formulations of canola oil are billed as having no trans or partially hydrogenated fats, because they weren't present prior to the refining process.

Another selling point for canola oil is that it can stand high heat without burning, and is thus well suited for deep-frying. Because of this, canola is often considered a preferred alternative to olive oil for very hot cooking. But the oil's large percentage of polyunsaturated fats will oxidize in high heat, turning them rancid. Meanwhile, the widely followed prohibition against frying with olive oil is misplaced. Extra-virgin olive oil has been deep-frying food in Mediterranean diets for centuries. Interestingly, the Canadian Canola Council lists the smoke point for extra virgin olive oil at 331 degrees, despite the fact that most sources pin the smoke point of good quality extra-virgin olive oil above 400 degrees, which will deep-fry anything.

One thing that's certain is that canola oil is low in saturated fat. And according to the medical community's party line, that's a good thing because saturated fats cause obesity and heart disease.

The Mayo Clinic often invokes the Mediterranean diet on its Web site, recommending "Mediterranean-style cooking" for "heart-healthy eating," and the replacement of butter with "healthy fats such as olive oil and canola oil." And thus, the long-lost fatty twins are reunited again, in your heart-healthy lasagna.

But there's nothing close to a scientific consensus about the supposed superiority of unsaturated fats with regard to obesity and heart disease. Many parts of these arguments are currently being debated.

Is the debate influenced by canola's tremendous profitability? Worldwide production is hitting record highs almost every year. And in just a few short decades of life canola oil has leapfrogged in popularity over other unsaturated oils like safflower -- which is lower in saturated fats than canola oil -- and grapeseed, which, for what it's worth, is from the Mediterranean. To what degree this surging popularity is due to the zealous pursuit of unsaturated omega-3 fats or to the marketing genius of the salesmen is a question for the cookbook authors who began recommending the oil in droves in the 1980s. Although in 2006 one such messenger, Andrew Weil, called canola oil a "distant runner-up to olive oil." Weil writes, "We have a wealth of evidence showing that populations that consume good quality olive oil as a primary dietary fat have significantly lower rates of both heart disease and cancer than those that don't. We have no comparable epidemiological data for canola. Also unlike extra-virgin olive oil, canola oil doesn't contain the antioxidant polyphenols that are protective against heart disease and cancer."

Olive oil has flavor; canola is tasteless. Olive oil is intact, alive with enzymes and other biomolecules, while canola is processed, filtered and separated into a sliver of its former self. Olive oil is the ancient foundation of the Mediterranean diet; canola oil is a recent experiment, a Hail Mary effort to save an industry.  

But for all of its wonderful qualities, one thing extra-virgin olive oil isn't is cheap. And canola oil, while perhaps not as mind-boggingly awesome as some would have us believe, probably isn't that bad for you -- except for those trans fats created in the deodorization process. But other than the price difference, there isn't any reason to choose canola oil over olive oil. It's a truly inferior product, despite what so many recipes imply.  

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