So much of what’s in processed food isn’t there because food manufacturers independently decided to use it but because food manufacturers reacted to pressure from government agencies. In no circumstance is this more evident than with cooking oils.
Due to the misguided and scientifically unsubstantiated demonization of saturated fats over the last century, a myriad of plant-based polyunsaturated oils have been mass-produced and put into nearly every packaged food in existence. But are these processed oils really more healthy than the fats and oils they replaced?
Fats are a macronutrient vital to humans. All omnivores derive fats from both animals and plants. In animals, fatty acids are found naturally in the flesh of meats and fish, within egg yolks and in mammals’ milk. Plants contain fats in the form of oils. Oil in most plants is contained in the nut or seed but some plants have oils in the flesh of their fruit.
There are two types of fats: saturated and unsaturated. Unsaturated fats are further categorized as either monounsaturated or polyunsaturated. A fat’s classification is based on its chemical structure. To simplify, saturated fats are the most stable and polyunsaturated fats are the most unstable. What that means is stable fats have a naturally longer shelf life and can be used for cooking without burning. Whereas unstable fats go rancid more quickly and can’t withstand heat. They’re best consumed fresh. Animal fats are predominantly saturated, with lesser amounts of unsaturated, while plant oils are mostly polyunsaturated with some monounsaturated and saturated exceptions.
Post World War II, some in the scientific community hypothesized that the growing rate of heart disease in Western cultures was due to consumption of animal fats and saturated plant fats. Even though clinical studies didn’t bear this out, a few highly publicized epidemiological studies seemed to support the hypothesis. (Decades later, these studies were discovered to have significant data flaws.) The idea that saturated fats caused heart disease became an accepted fact and the push was on to extract and stabilize polyunsaturated plant oils to be used in packaged foods and bottled for home cooking. Hello shortenings, margarines and corn oil and, eventually, soybean and canola oils.
With the exception of soybean oil, plant oils can be extracted from the seed, nut or fruit by pressing it. However, to speed up the process, manufacturers of mass-produced plant oils extract the oils by using a solvent, usually hexanes. Though hexanes are considered non-toxic and evaporate during the refining process, one could hardly consider oils that have been through this process “natural” or minimally processed.
Regardless of whether the oil is extracted through pressing or applying solvents, the oil usually goes through some or all of the following refining processes: stabilizing, de-gumming, neutralizing and bleaching. Remember, most of these oils are 50-100% polyunsaturated fats and, therefore, considered unstable. The refining process must be done to prevent spoilage and withstand heat. It also neutralizes odors, colors and off-tastes. The refining process is diagrammed here:
Hydrogenated Oils: The practice of adding hydrogen to stabilize oils was widespread until clinical studies suggested a link between them and disease. In response, some manufacturers replaced the hydrogenation process with other refining processes (shown above) to achieve stabilization. Though many packaged foods still contain hydrogenated oils and are considered unhealthy. They’re listed as hydrogenated or partially-hydrogenated in the ingredient list and as trans fats in the Nutrition Facts label on packages.
Oils: Most Processed to Least Processed
Soybean Oil: Because these seeds are small and contain very little oil, the oil can’t be extracted through pressing. Therefore, all soybean oil is extracted through the use of solvents and goes through the entire refining process. Because of soybean abundance and government subsidies, this highly processed polyunsaturated oil is ubiquitous. Unless one makes all her food from scratch and avoids all chain restaurants, it’s nearly impossible to rid one’s diet of soybean oil.
Seed Oils: Oils from most seeds can be extracted through pressing to avoid chemical extraction. But chemical extraction produces a higher yield per seed as compared to pressing. Therefore, most mass-produced seed oils go through the entire refining process, including the solvent phase. It’s possible to find bottled oils and packaged products that use pressed seed oils. They would be listed as expeller-pressed or cold-pressed oil on the ingredient list. One should assume, however, that unless it’s also listed as unrefined, the oil has been put through the stabilization, neutralization and bleaching processes to extend shelf life, withstand heat and remove odor, color and bitterness. Common seed oils (>50% polyunsaturated, unless otherwise specified):
- Sesame (50:50 mono to polyunsaturated)
- Palm Kernel (palm tree seed)
- Corn (extracted from corn kernel germ)
- Canola (extracted from a variety of rapeseed plants such as turnip & cabbage; rapeseed is >50% monounsaturated)
Nut Oils: Like seed oils, nut oils can be extracted via pressing or solvent treatment. But because they tend to be larger than seeds and contain more yield compared to seeds, it’s easier to find pressed nut oils for the home. But most industrial nut oils used in packaged products and in restaurants are solvent extracted. Again, even if they’re pressed, unless they’re listed as unrefined, they likely have gone through stabilization, neutralization and bleaching. Common nut oils:
- Peanut (>50% monounsaturated)
- Walnut (>50% polyunsaturated)
- Almond (>50% monounsaturated)
Fruit Flesh Oils: These are easily extracted through pressing and are the least processed plant oils. Because they’re either monounsaturated or saturated oils, they don’t need to be stabilized. Be sure to choose virgin, extra-virgin or unrefined versions to ensure they haven’t been neutralized or bleached. Common fruit flesh oils:
- Olive (monounsaturated)
- Avocado (saturated)
- Coconut (saturated)
- Palm (saturated)
And, of course, there’s animal-derived butter (saturated fat) which contains churned cream with or without salt – no chemicals, no refining process.
Now that you know how cooking fats and oils are made, I’ll let you decide which you think are healthiest for you and your family.
Sources: WiseGeek.com, Madehow.com, Kitchn.com, Wikipedia.com