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Olive oil comes from olives, corn oil comes from corn and canola oil comes from ... canola?
Right... sort of. Canola oil is a genetically modified food made from a hybridized version of the rapeseed plant which is a member of the mustard or cabbage family.
Rapeseed oil is a low quality monunsaturated oil used mostly in industrial applications and in some traditional Japanese, Indian and Chinese cultures. The problem with rapeseed oil is that it's high (30 to 60%) in a toxin called erucic acid, found to be associated with fibrous heart lesions.
In the late 1970's, when polyunsaturated fats from vegetable oils were beginning to be shunned for their association with high rates of cancer and heart disease, monounsaturated fats like olive oil were being relied on more and more as the best source of healthy monounsaturated oil. However, there was not enough olive oil for world demand, not to mention that it was too expensive for producing cheap processed foods.
Canadian researchers came to the rescue by engineering a new plant from the rapeseed plant which was lower in erucic acid. It was eventually called "canola," short for Canadian oil, low [erucic] acid.
The Canola Council of Canada defines canola as
...an oil that must contain less than 2% erucic acid, and the solid component of the seed must contain less than 30 micromoles of any one or any mixture of 3-butenyl glucosinolate, 4-pentenyl glucosinolate, 2-hydroxy-3 butenyl glucosinolate, and 2-hydroxy-4-pentenyl glucosinolate per gram of air-dry, oil-free solid.
Sounds yummy! Canola oil was marketed to healthcare professionals and consumers as a health product high in monounsaturated fats and Omega-3 fatty acids, and low in saturated fats.
In 2006, the FDA allowed canola oil and products containing canola oil to be labeled with heart health claims. Labels can say that limited evidence suggests that eating 19 grams (about 1.5 tablespoons) of canola oil daily in place of saturated fat may reduce the risk of heart disease as long as you don't increase your total caloric intake.
It was quickly embraced as a cheaper alternative to olive oil and endorsed by such health gurus as Dr. Andrew Weil. However, since then Dr. Weil has modified his view, calling canola oil a distant second choice to olive oil and pointing out that there are no long term studies on the effects or benefits of canola oil:
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 anti-oxidant polyphenols that are protective against heart disease and cancer.
Critics of canola oil are vocal and passionate. Sally Fallon of the Weston A. Price Foundation agrees that there are no long-term human studies and concludes from a review of laboratory studies that:
...canola oil is definitely not healthy for the cardiovascular system. Like rapeseed oil, its predecessor, canola oil is associated with fibrotic lesions of the heart. It also causes vitamin E deficiency, undesirable changes in the blood platelets and shortened life-span in stroke-prone rats when it was the only oil in the animals' diet. Furthermore, it seems to retard growth, which is why the FDA does not allow the use of canola oil in infant formula. When saturated fats are added to the diet, the undesirable effects of canola oil are mitigated.
Other critics complain that the oil is highly processed, that it is genetically modified, contains traces of hexane from the extraction and refining process, and in general is an imitation food.
Notwithstanding, the American Heart Association continues to bless the use of canola oil.
What's a consumer to do? Why bother with an unproven food invention? Stick with tried and true olive oil.