We have been through quite a journey and it is not over!

We have learned why fats are important for our bodies and which fats are essential and in what ratios. We have learned about good, bad, and ugly fats. We touched on the molecular chemistry of fats.

Now, we are going to learn how cooking oils are processed and, after that, why rancid oils are bad for us.



  1. (of foods containing fat or oil) smelling or tasting unpleasant as a result of being old and stale

We know that polyunsaturated oils are unstable once they leave their place in nature. Well, this created a problem when the cooking oil manufacturers want to bottle them and sell them. These oils would naturally go rancid quite quickly.

Enter chemistry. Here we have man stepping in again so that they can create shelf-stable products cheaply and make big money.

This image shows the process quite well. Follow along on the chart while you read the step-by-step breakdown of the process. (Image source: http://www.madehow.com/Volume-1/Cooking-Oil.html)

Get ready to know more than you ever wanted to know about vegetable oils!

To keep these oils from going rancid:

  • First, seeds or grains are cleaned, ground, pressed, and heated to make the extraction process easier.
  • The extraction process then begins using a solvent called hexane, which is what they use to dry clean clothes! Manufacturers like hexane because it can efficiently extract almost 100% of the oils from the plants. Wondering why you don’t see hexane on the ingredient label? It evaporates during processing, so it is not required to be listed, but we won’t mention the traces that remain in the oil after processing and refining! (oops, or did we!?)
  • After extracting, the oil stinks and tastes bitter, and it doesn’t have a very nice color to it, either. It is basically rancid, so all the naturally occurring substances in the oil need to be removed. If left in there, your oil would foam, pop, or smoke when heated. Can’t have that!
  • The oil is then heated AGAIN, and chemicals are used to “clean” the oils. These chemicals include (but are not limited to) bleach, defoamers, and degumming agents.
  • Now, because the natural and healthy antioxidants have been stripped from the oil during processing, there is not protection from it returning to its bitter, stinky, ugly state, so the manufacturer adds TBHQ, BHA, and/or BHT. These are all chemical preservatives that have been known to cause cancer.

These processed oils did not exist until the 1930s, yet our current diet can contain up to 30% of our daily calories from these oils.

Over-consumption of these oils leads to a large number of illness and diseases like:

  • Cancer
  • Heart disease
  • Compromised immune system
  • Liver damage
  • Digestive disorders
  • Diseases of the reproductive organs
  • Lung diseases
  • Weight gain

Just consider the difference when you eat a handful of raw sunflower seed versus when you eat a handful of tortilla chips. The sunflower seed contains healthy, unadulterated polyunsaturated oil, but the tortilla chip that has been deep fried in processed sunflower oil gives you free radicals, damaged cells, and poor health.

This is another reason our health depends on us decreasing processed foods while increasing the amount of whole foods we consume…especially those veggies and fruits that are full of free-radical-fighting antioxidants!

Next up, free radicals and their effects on our body.