The main difference between a monosaturated fat and a polyunsaturated fat is in their molecular structure. Mono fats are linked by one molecular bond; polys are linked by many. Multiple bonds are highly unstable, and contribute to oxidative stress and free radical damage, the precursors to most chronic disease.
Poly fats are especially volatile if at all processed, and even when exposed to light, moisture, air or heat. It’s important to understand the havoc wreaked when cooking with oils like soybean, canola and corn – these oils virtually unleash free radicals in the body. Unfortunately, restaurants use these cheap oils extensively, and people mistakenly think “healthy” when they hear “cooked in vegetable oil.”
The clear and odorless oils you see on grocery shelves are first put through high heat processing, then bleached and deodorized. They are simply industrialized oils and contribute to the development of chronic disease.
Being high in Omega 6 fatty acids, poly oils can crowd out the very important, health promoting Omega 3 fatty acids. Most processed and/or fast foods are loaded with Omega 6 fatty acids.
It’s no accident that the increase in heart disease coincides with the discontinuation of monosaturated fats and the introduction of polyunsaturated fats into the American diet. Prior to the 20th century, when people principally consumed butter, coconut and palm oil, there was virtually no heart disease. But because the modern oils like corn and canola oil are cheaper to manufacture, they were touted as “safe and healthy” and began to replace the monos, who were given a bad rap.
Also, keep in mind that all oils become rancid when exposed to light, air, and heat. It is best to store any oil and oil-based food in the fridge or freezer, and this includes nuts and even vitamins that have an oil base, like Vitamin E or fish oil. If you do want to cook with oil, try to use oils that can withstand the heating process, like peanut or coconut oil. Buy organic and cold pressed oils packaged in darker, opaque containers. Face fats – all fats are not equal.