I first became aware of the danger of cooking foods in vegetable oils when I saw an article in the Sydney Morning Herald on9 November 2015, p.2. It has taken a little time, but I have tracked down the source. I wanted to make sure that the information was accurate. It appears that it was. This is the material I found at the following site on 10 March 2016:
“Volunteers were given sunflower oil, vegetable oil, corn oil, cold-pressed rapeseed oil, olive oil, butter, goose fat and lard and asked to use them in every day cooking. They collected any leftover oil and sent it to DMU’s labs to be analysed. When fats and oils are heated the molecular structure changes, producing chemicals called aldehydes that may cause heart disease and cancer.
“Professor Grootveld’s team found sunflower oil and corn oil produced aldehydes at levels 20 times higher than recommended by the World Health Organisation. Olive oil and rapeseed oil produced far fewer aldehydes as did butter and goose fat. Not only that, but Professor Grootveld’s team also identified two previously unknown aldehydes in the samples of these oils – a world first.
“He said: “Sunflower and corn oil are fine as long as you don’t subject them to heat, such as frying or cooking. It’s a simple chemical fact that something which is thought to be healthy for us is converted into something that is very unhealthy at standard frying temperatures.”
He recommends olive oil for frying or cooking: “Firstly, because lower levels of these toxic compounds are generated, and secondly the compounds which are formed are less threatening to the human body.” (I have added the bold)
Presenter Michael Mosley said: “Put simply, cooking with these oils is producing even more toxic compounds than has ever before been realised. In contrast, the olive oil and cold-pressed rapeseed oil produced far fewer aldehydes, as did butter and goose fat. The reason being that these fats are richer in monounsatured and saturated fats, and are much more stable when heated. I was surprised as I’d always thought of sunflower oil as being ‘healthy’.”
Professor Grootveld has been carrying out research in this area for many years and is a respected consultant for a wide variety of healthcare, pharmacy and food companies.
It seems to me that “rapeseed oil” is canola oil. Professor Grootveld is from De Montford University, Leicester
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