poisonous canola oil
Ever since the late 1990s, when canola oil started to become a ubiquitous ingredient in food processing and restaurant fare, consumers have been ingesting it, literally, by the tons!

Canada produces 20 percent of the world's canola oil. The U.S. imports an average of 510,000 tons of canola oil per year!

Canola is a heated and processed oil using anywhere from 80 - 90°Celsius and even 120°Celsius temperature in the processing, or 176 - 194° Fahrenheit to 248° Fahrenheit. That would be in addition to any additional heating a cook uses when preparing foods—something to factor in to your cooking.
Christened "Canola" from "Can" (for Canada) and "ola" (for oil low acid), canola is not, strictly speaking, rapeseed. There is a internationally regulated definition of canola that differentiates it from rapeseed, based upon its having less than two percent erucic acid and less than 30 umoles glucosinolates. Oilseed products that do not meet this standard cannot use the trademarked term "Canola." [1] [CJF emphasis]
That 2 percent of erucic acid gets a lot of human digest tracts very upset, I've found as a nutritionist! The Free Medical Dictionary by Farlex defines erucic acid as:
a monounsaturated fatty acid that is a major constituent of certain oils, such as rapeseed oil. Because it [erucic acid] has been linked to cardiac muscle damage, oils such as canola oil were developed that are low in erucic acid. [2].
At one time, rapeseed oil was not permitted to be sold in the USA by the U.S. FDA, because of its toxicity.

By the way, there was a petition [3] that was delivered to Whole Foods about their using canola in all the edible products they make and sell, including its fresh food and soup bars! As an aside, since the late 1990s, I was in contact with Whole Foods various VPs about using canola oil. The letters I received from WF, in my opinion, showed shamefully woeful concerns for human health issues. Whole Foods was more concerned about the costs of producing products. I have refused to purchase any food products from Whole Foods since then, which contain canola oil, e.g., their "organic canola oil" is bunk, in my opinion.

Recently Mike Adams, the Health Ranger and editor of Natural News, featured a short exposé of canola oil, which I cite below:
Organic canola oil is a healthy choice [No way!]

Everything organic is not healthy. Let's go there. Organic means it doesn't contain chemical-based insecticides, algaecides, fertilizers and herbicides. What it doesn't mean is that it's free of heavy metals or trace amounts of dangerous chemicals. Canola is not a natural plant to this earth. Canola comes from rapeseed, which is toxic to all animals. What the manufacturers do is remove the stench of rapeseed using hexane, a constituent vapor of gasoline, but there's still some left in the final product. Irrespective of whether canola is organic or not, it strangles your mitochondria (cells) that need oxygen to function. Organic canola also inhibits enzyme function. Plus, the omega-3 fatty acids of processed canola oil are transformed during the deodorizing process into trans-fatty acids. The reason why canola is particularly unsuited for consumption is that it contains a very long-chain fatty acid called erucic acid, which is associated with fibrotic heart lesions.

Additionally, canola oil is hard on, and disruptive to, the entire digestive tract, especially those with irritable bowel syndrome (IBS) and other allergic-type reactions. I contend it's inflammatory too! [4] If you have any digestive problems, remove all processed foods, canola use in any form, and see if you don't get relief! That applies, particularly, to children on the Autism Spectrum Disorder (ASD). So many clients and other folks have thanked me for pointing out canola, especially since everyone buys into the pap that canola is supposedly 'healthy'.

Question: So, really, why do Whole Foods and other organic and natural food sellers use canola oil (organic and non-organic) in the foods they make and sell?

Probable Answer: Most likely propaganda 'shirt-tail riding'; it's cheap and supposedly sounds 'healthy'.

Safer cooking oils to use include only organically-grown oils: cold pressed olive oil; sunflower oil; grass fed/raised butter; safflower oil. Virginolais a combination of olive and either canola or soy oils, which restaurants use and pass off as "olive oil". Keep that in mind when dining out. Ask questions.

High heat cooking with any oil creates carcinogenic byproducts in foods. Don't deep fry food. Tropical oils, in my opinion, are questionable for many who have sensitive digestive tracts, which is almost everyone today due to so many years of ingesting canola oil as a 'healthful product'. Most tropical oils also are highly processed oils. They have to be because oil is not found as a free-flowing product in Nature. Oil and fat always are encased in some type of tissue: plant or animal. It has to be heated and processed to keep it in a free-flowing state.

Some of the carcinogenic byproducts produced from cooking with high heat oils can be found here and here.

In my July 2016 book, Eat to Beat Disease, Foods Medicinal Qualities, I provide an in-depth chapter on cooking oils, their dangers and digestive problems. That chapter is titled "A Greasy Story about Cooking Oils."

We need healthful-giving oils in our diets; not rancid, over-processed, heated, hexane-treated vegetable oils, I offer.

[1] http://www.soyatech.com/canola_facts.htm
[2] http://medical-dictionary.thefreedictionary.com/erucic+acid
[3] https://www.change.org/p/whole-foods-stop-using-canola-oil-in-foods-you-make-and-sell
[4] https://www.bewell.com/blog/canola-oil-a-healthy-oil-fraud/