It looks at first sight that many vegetable oils have high levels of the so-called essential fatty acids, omega-3 and omega-6, and are thus marketed as healthy oils to be used in our diet. There has to be a fine balance between omega-6 and omega-3 since omega-6 tend to increase the production of pro-inflammatory prostaglandins while omega-3 tend to be the reverse. A healthy ratio of omega-6 to omega-3 may be 4:1. Most of our vegetable oils contain an excess of omega-6 which is detrimental to our health.
Negative effects of processing
On deeper analysis however, the detrimental effects of processed vegetable oils are much more profound than the ratio of omega-6 to omega-3. These polyunsaturated fatty acids, by the presence of the double bonds their molecules, are easily damaged. They become oxidized and turn rancid.
The damage occurs in the presence of heat, light and oxygen. Thus, unless careful measures are taken during the extraction and processing of these vegetable oils, the end products contain a high percentage of damaged fatty acids which are detrimental to our body. This is what happens in the large scale industrial processing of soybean, sunflower, corn, canola and peanut oils.
The processing involves also using deodorizing and bleaching agents which may remain in small amounts in the finished products. Contrast this to the gentle cold compression of virgin olive oil. Thus, virgin olive oil is truly virgin in preserving the natural, undamaged oleic and polyunsaturated fatty acids. However, with high heat, even this can be damaged.
Since modern day industrial processing of seed oil damages polyunsaturated fatty acids, the higher the content of polyunsaturated fatty acids, the greater the damage in the finished products. These are what edible oil industry wants to get everyone to use instead of the traditional oils including animal fats and tropical oils.
Even when polyunsaturated fatty acids are not damaged, they should never be used in high temperature cooking including frying, baking and deep frying. Furthermore, repeated heating damages the oils even more. Modern fast food restaurants use a lot of vegetable oils in their cooking. Is it any wonder that we are now faced with numerous problems and diseases which can be traced directly or indirectly to the consumption of processed, damaged vegetable oils?
This sorry state of affairs has prevailed partly due to the ingenuity of man in finding a solution to the problem of surplus, excess vegetable seed oil. In the nineteenth century, seed oils including soybean oil were used in paints. Some clever chemist then invented a method to make cheaper paint from petroleum waste products. The seed oil industry was left with excess vegetable oils with no avenues for disposal.
At the time, the majority of the population was consuming large quantities of animal fats. Early in the 1950’s Ancel Keys suggested, on his observation of arterial disease, that saturated fat and cholesterol were the cause of heart disease. Substituting saturated animal fat with vegetable oils appeared to reduce the cholesterol level and thus arterial disease. The seed oil industry thus seized on this preliminary observation to promote their oils as heart healthy. Even though subsequently these were found to be contentious, the industry has become so powerful and so established that it is well-nigh impossible to say otherwise.