Recent media: “Cooking with vegetable oil releases toxic chemicals linked to cancer”.

Heating up vegetable oils led to high concentrations of chemicals called aldehydes, which have been linked to illnesses including cancer, heart disease and dementia according to UK scientists. In contrast, heating up butter, olive oil and lard in tests produced much lower levels of aldehydes. Coconut oil produced the lowest levels of the harmful chemicals. It is important to note that these were chemical tests on oils, not trials involving humans.

What should failsafers do? Well, don’t panic - half of all nutritional advice is likely to be seen as nonsense within 10 years and canola oil, which is recommended for failsafers, still looks much better than the corn and sunflower oils implicated in the report. Coconut oil, by the way, is high in salicylates and amines, so obviously not failsafe.

Fats and oils are complicated by contradictory research reports but there are three things to consider: the ratio of omega-6 to omega-3 fatty acids (fats and oils are made of smaller units called fatty acids; omega-6 and omega-3 classes are as essential for health as vitamins), the amount of mono-unsaturated fatty acids, and the amount of saturated fatty acids. The length of the fatty acids may also be an issue.

There is reasonable evidence that humans evolved on a diet with a ratio of omega-6 to omega-3 of approximately 1:1. Of all commercial fats and oils, canola is closest to this with a ratio of 2:1. Corn oil is 57:1 and sunflower oil is 71:1. Coconut oil, which is currently fashionable for marketing reasons, has no omega-3 so a ratio cannot be calculated. Rice bran oil is 17:1.

Mono-unsaturated essential fatty acids are regarded as protective for heart disease with anti-inflammatory and anti-oxidant properties. Of all commercial fats and oils, canola, safflower and olive oil are the highest (61-75%). Coconut oil (7%), butter (28%) and lard (47%) are all lower. Rice bran oil is 38%. Olive oil is not failsafe due to the presence of salicylates, so canola is still looking good.

The advice from the Heart Foundation of Australia remains that saturated fats increase cholesterol in your blood, particularly LDL cholesterol (the ‘bad’ type). Replacing saturated fat with unsaturated fat reduces the risk of heart disease and stroke. Canola has only 7% saturated fat, the lowest of all commercial fats and oils. Coconut (91%), butter (68%) and lard (43%) are all far higher. Rice bran oil is 25%.

Trans fatty acids (TFAs) from partially hydrogenated vegetable oils have clear adverse effects and should be eliminated. Naturally occurring TFAs are found in some animal products including butter, cheese and meat. They are largely not present in retail vegetable oils but some commercial products still contain them.

What can I do if I am concerned?

Minimise frying as a means of cooking food. Use smaller amounts of oil and avoid deep-frying. Steaming, boiling and baking avoid the high temperatures that produce potential carcinogens.

Minimise re-use of frying oil. Use it once and discard. Keep temperatures low to minimise production of harmful aldehydes and other carcinogens.

Adopt a lower fat intake. Many so-called low fat diets still provide 30% of your daily calories as fat; a genuine low fat diet should be 10%.

Some references: 

Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002 Oct;56(8):365-79. 

Simopoulos AP. The importance of the omega-6/omega-3 fatty acid ratio in cardiovascular disease and other chronic diseases. Exp Biol Med (Maywood). 2008 Jun;233(6):674-88. doi: 10.3181/0711-MR-311. for ratios


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