Be Careful of Canola 

Relatively unknown just a decade ago, canola oil is now found in many foods, especially health foods, and it is considered by many nutritionists as one of the healthiest cooking oils. Canola oil is thought to be the second highest vegetable source of the beneficial omega-3 fatty acids—nutrients reputed to boost heart health by effectively lower serum triglyceride levels and reducing platelet aggregation. In addition, canola oil is high in monounsaturated oleic acid, a cholesterol-reducing substance. 

Despite canola oil’s healthy reputation, popular acceptance, and excellent nutritional composition, it may be toxic when used in cooking. This is because omega-3s, one of canola's nutritional strengths, become damaged if the oil is heated. Whether through cooking or processing, heating distorts the omega-3 molecules, converting them into the trans form that can elevate total cholesterol, and lower the good HDL cholesterol. 

Refined canola oil, typically found in conventional food stores, is usually exposed to high temperatures, deodorizing and bleaching. Its health-giving constituents are processed away, and its omega-3s converted into the undesirable trans form. Even "lightly refined" and "expeller pressed oils can be exposed to deodorizing, which may raise the oil temperature to a sizzling 450°–470° F. 

The best way to enjoy the health benefits of canola oil is to buy the unrefined variety, and use it exclusively in cold preparations, such as salad dressings. Other, more heat-resistant oils, such as extra Virgin olive oil, unrefined sesame oil or high-oleic sunflower oil are better for cooking. 

[Editor: Canola oil is made from a strain of rapeseed—a naturally toxic plant—that has been bred to be nontoxic. Some people do not trust that all the toxins are removed, and, therefore, do not use canola oil in any form.]