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Canola oil is a vegetable oil derived from the rapeseed plant (Brassica napus), a species of the Brassica genus that includes turnip, mustard, and colewort. The genus includes cabbage, cauliflower, broccoli, and kale. The unfortunate name comes from the Latin rapum, meaning turnip. The more marketable name comes from its home country of Canada.
Unlike standard rapeseed oil, which has relatively high levels of cardiotoxic fatty acids such as erucic acid and is used in the West only for industrial purposes, canola is derived from special breeds of the rape plant selected for low levels of erucic acid. Even the typical levels of erucic acid would probably do only slight damage to adults, but the "adults" wouldn't stop whining about its bitter taste, so it was bred out.
Some people who get their knickers in a twist about almost any new food plant don't like canola oil very much, which is a shame because it's a nice substitute for olive oil where the olive flavor would be too much and it has a higher smoke point than most oils as light, making it ideal for deep-frying. (It does smell a bit weird when hot though.) It's also got just about the lowest saturated fat content of any cooking oil on the market, and is the only oil with a smoke point above 350°F with a significant amount of omega-3. Detractors like to refer to it using the strictly correct but blatantly loaded term "rape oil", a choice of terminology that would make Newt Gingrich proud.
Most canola oil is processed using hexane, a chemical derived from petroleum. Hexane is not carcinogenic in rodents. Even the industry admits that some amount of hexane remains in the finished product, but claims the amounts are "insignificant".
The main bugaboo with hexane is that though it's technically natural — extracted from naturally-occurring petroleum — it does not meet the definition of organic according to some, and hence to them canola oil labelled as organic is an oxymoron.
It's important to note, though, that hexane is used in the processing of many different vegetable oils, not just canola oil. Soybean oil — and for that matter, soy protein — are also processed using hexane. The food processing industry is looking into replacing the regular hexane they're now using with isohexane. Also worth noting is that hexane boils at a much lower temperature than cooking oil and should not be present after the oil is heated to cooking temperatures, and also that consumption of the raw oil is not the usual practice.
Trans fat production
While raw canola oil contains only 0.4% trans fat, by the time it's processed, bottled, and sold, this rises to nearly 2%. This is still a small enough amount to qualify as "0g trans fat per serving" for both American (1 tbsp) and Canadian (10 mL) labelling laws.
Some claim that heating polyunsaturated fats, such as those found in canola oil and soybean oil, creates even more trans fats, therefore cooking with canola oil sentences you to an early grave. Others claim that this is a load of malarkey. According to a 1993 journal article, you have to heat a polyunsaturated oil to 245°C for 16 hours before it begins to trans-isomerize into trans fats – and even then, only a very small percentage (less than 1%) are converted.
If the canola oil is subjected to partial hydrogenation, that's a whole different kettle of fish, of course. That'll produce more than enough trans fat to show up on a nutrition facts label. But then, it can no longer be called "canola oil" on an ingredients list; it has to be listed as "hydrogenated canola oil" or "partially hydrogenated canola oil."
Genetic modification, oh noes!
All canola is genetically modified food, in the sense that the modern canola plant is the product of selective breeding and cross-breeding. Varieties of rapeseed that produced little or no erucic acid were selected and bred, and their most desirable (i.e. lowest erucic acid) descendants were chosen to breed in the next generation, until the modern plant was produced.
However, starting in the 1990s, new varieties started to be developed by more direct genetic engineering — i.e. by actual gene splicing/DNA recombination. By the late 2000s, around 90% of all canola seeds planted in the U.S. and Canada carried genes that had been spliced into either their own seeds or the seeds of their ancestors.
Thus far, the only such genetic modification made to canola seeds is the ability to tolerate herbicides (weed killer). This allows canola farmers to kill the weeds that harass their canola crops by spraying the entire field with glyphosate (AKA RoundUp™), without fear of killing their crops with the stuff too. This particular genetic modification is known in the biz as the "Roundup Ready trait". However, pollen from these genetically-modified canola plants soon made its way out into the wild, either because the crops scattered their pollen or because seed-hauling trucks accidentally spilled some of their cargo or both. By 2010, 80% of wild rapeseed plants in North Dakota carried transgenes for herbicide tolerance. This raised concerns that the build-up of herbicide resistance in feral canola could make it more difficult to manage these plants using herbicides.
The gene(s) for herbicide tolerance spliced into the canola plant do, of course, change its protein makeup slightly. However, since it is only the oil of the canola plant that is sold as food, and not any of the protein-bearing portions, the potential for the new GM-introduced proteins to cause allergic reactions has not been investigated. So far as as is known, the chemical composition of the oil has not changed.
- Snopes.com on canola oil
- Canolainfo.org Processing Canola Oil - Page 6 - Hexane Extraction of Canola
- Rape, Online Etymology Dictionary.
- Or so they™ keep telling you; but according to the Wikipedia entry at http://en.wikipedia.org/wiki/Canola#Comparison_to_other_vegetable_oils its smoke point is actually lower than that of soybean oil, corn oil, or even safflower oil.
- Chronic inhalation carcinogenicity study of commercial hexane solvent in F-344 rats and B6C3F1 mice by W. Daughtrey et al. Toxicol Sci. 1999 Mar;48(1):21-9
- Natural News: Organic canola oil; Is that an oxymoron? Caution: NaturalNews
- Canola Oil: The blob that ate butter, olive oil, coconut oil and peanut oil threatens American cuisine, from a paleo diet webpage
- Trans Fatty Acids Are Not Formed by Heating Vegetable Oils, from a 2004 article on the Weston A. Price Foundation site
- Przybylsk et al., Formation of trans fats during food preparation, Canadian Journal of Dietetic Practice and Research, 2012 Summer, vol. 73 no. 2, pp. 98-101
- Wolff, R. L. 1993. Heat-induced geometric isomerization of alpha-linolenic acid: effect of temperature and heating time on the appearance of individual isomers, Journal of the American Oil Chemists Society, vol. 70 no. 4, pp. 425-430.
- Beckie, Hugh et al. (Autumn 2011) GM Canola: The Canadian Experience Farm Policy Journal, Volume 8 Number 8, Autumn Quarter 2011. Retrieved 30 December 2012
- Johnson, Stanley R. et al Quantification of the Impacts on US Agriculture of Biotechnology-Derived Crops Planted in 2006 National Center for Food and Agricultural Policy, Washington DC, February 2008. Retrieved 30 December 2012.