Vegetable oils or polyunsaturated oils like corn, soybean, canola, safflower and sunflower are often referred as “healthy” oils.
Let us start clarifying that these oils do not come from vegetables, actually they should be called seed oils because they are crushed out of seeds or beans. Lately we have been told that in ketogenic diets we should consume a diet high in fat and low in carbohydrates. Moreover we are told these oils are healthy but is it really true? According to the dietary guidelines for Americans 2015-2020 it includes: corn oil, cottonseed oil, soybean oil, safflower oil, peanut oil and canola oil as recommended fats. American have done a good job following this guideline, In the course of the 20th century the consumption of oil has dramatically increased over one hundred twenty one thousand times. This is due to the fact that at the beginning of the 20th century we did not consume these products.
A little history on oils.
Centuries ago the fats we consume were lard and butter, the production of oil came from whales and was for used mainly for machinery. Oils were not something that humans consumed. Eventually a new source of oil was found and we started producing cotton seed oil.
Chemistry on fatty acids.
Unsaturated fatty acids are found in oils and they possess double bonds between carbons molecules. Double bonds are not stable and create a rupture in the chain and are not stable.
Saturated fatty acids like the ones we find in meat, cheese and butter do not have any double bonds and they are solid at room temperature.
Unsaturated fatty acids are unstable because they have the potential to react with oxygen.
In the early part of the 1900’s, In United States a new way was found to make unstable molecules stable with a process called hydrogenation, this long process consisted of pressing the cottonseed oil out resulting in a gray sludgy mixture that has to be steamed to eliminate bad odors then bleached and winterized for stability to then be enhanced with artificial color and synthetic vitamins. This discovery allowed companies to sell this product for human consumption because of its resemblance to lard. Crisco was the result of this process of hydrogenation. Thanks to its marketing campaign it became very popular and the idea was that this product stood for the future and was also approved by scientists. Later on, Crisco was modified with salt and yellow color and the margarine was incorporated into our lives.
In 1961, the American Heart Association advised to limit saturated fats to prevent heart disease and we were introduced to the the the idea that polyunsaturated fats as medicine to lower cholesterol. However in the middle of the 20th century studies suggested that the rise of vegetable oils had an impact on heart disease. In the 1960’s and 70’s studies were made by governments around the world and the results claimed that no effects of saturated fats were found on cardiovascular mortality or total mortality. On the other hand when it comes to studies on polyunsaturated oils on animals they found in study published in 1972 that soybean when heated produced compounds that were highly toxic to mice. Rats which were fed mildly oxidized oils suffered liver damage and heart lesions compared to rats fed with tallow, lard, diary fats, which showed no such damage.
Linoleic acid is polyunsaturated omega 6 fatty acid that, when heated degrades into free radicals, degraded triglycerides and other oxidized decomposition compounds, one of them is called aldehydes which are known toxins that lead to heart disease, cancer, affecting DNA and RNA.
Which oils to use?
First of all, it is not advisable to cook with any oil because they are not stable, it is more advisable to cook with more stable fat like lard, butter and tallow. If you are going to use for salad dressing or sauce it is more recommended to use olive oil, flaxseed, macademia and avocado oil. However, the common ones we use are soybean oil, peanut oil, corn oil are very high in linoleic acid
In conclusion, we have to be conscious about which oils we are using and which meals are we consuming during the week, cooking oils have a direct impact in our bodies so next time you are at the grocery store take a look around and check for options that will make you live longer and healthier. Do not go for polyunsaturated oils, choose life.