Oils and fats essential to diet


In my columns thus far I’ve mentioned very little about the third leg of the nutritional triad — fats.

They’re an essential part of our diet, and oil is fat that is liquid at room temperature. Oils such as linolenic and linoleic acid are the starting points for some very important factors in our bodies.

Although edible oils have been made and used by man for thousands of years, very few people really understand just how oils are produced and what the different terms like “cold pressed,” “solvent extracted” or “virgin” means.

Oils carry fat soluble vitamins A, D, E and K. Fats of all kinds give satiety value to meals, helping us to be satisfied for longer periods of time. Oil can be extracted from nuts and seeds, certain vegetables and even from fish.

Let’s start by talking about the obvious oldest known and perhaps the most important one, olive oil. By reviewing the methods of extracting oil from olives we can apply that information to other media as well.

First, the food (called substrate) must be reduced to what is called a “mash” by grinding or mashing it to create a greater surface area to release the oils within. At this point several procedures of various complexities can be applied; we’ll discuss only the basics.


Hot water extraction, probably the oldest method of extracting oil, involved boiling the mash in water. The oil was allowed to rise to the surface and was then skimmed off.

The mechanical “cold pressed” method is also time-honored. When the mash is pressed, heat is naturally generated but not enough to affect the quality of the oil. Hence, “cold pressed.”

The mash is put into a press not unlike presses used to extract juice from wine grapes. As pressure is applied, the liquids within are squeezed out. This will be mainly water and the oil, which when allowed to stand will rise to the top of the water and eventually be skimmed off.

The first emissions when pressure is applied are called the “virgin” oil. There has been considerable debate on what “virgin” actually means in the olive oil business, but virgin and extra virgin oils will usually be the first oil from the press and will be darker, containing some of the olive residue, hence imparting a rich olive flavor. Some people desire this; others don’t.

Expeller pressing is also considered a mechanical method since it mechanically presses the mash through a fine sieve. The process does not generate much heat and is also considered a desirable way to extract olive oil.

There also is chemical extraction. The method also begins with the mash, but at that stage the mash is mixed with a solvent — usually hexane — that separates the oil from within the mash. After settling, the hexane and the oil are then separated.

Though hexane is a known carcinogen, manufacturers insist that all of the hexane is removed. I stay away from oil that does not state “cold pressed” because it will likely be chemically extracted.

I also advise steering away from cottonseed oil. To the best of my knowledge, there are no restrictions on sprays used in growing cotton. Hence, cottonseed oil may contain residues. Cottonseed oil is frequently listed on labels as “vegetable oil.”

Edible oil facts

Now let’s discuss some interesting facts about edible oils.

All oils have a characteristic referred to as being “unsaturated.” Although being nutritionally desirable it can easily lead to oil becoming rancid. Rancidity can in itself be very dangerous.

This may seem overprotective, but my recommendation has always been to not buy oil in a large container, because each time you open the bottle and pour out some oil, you also allow in an exchange of air that will eventually cause the remainder of the contents to become rancid.

One of the touts for olive oil is that it is a “mono-unsaturated” oil, which does not allow it to easily become rancid.

The next characteristic about oils is the “smoking point.” When an oil is overheated, depending on its own characteristics, it will begin to smoke.

Oils that reach the smoking point have chemically broken down enough to also be carcinogenic and dangerous.

Hence, when cooking, especially frying, never let your oil reach the smoking point!

True story: In one of my nutrition classes some years ago a middle-aged male student commented, “What you are saying Dr. ‘T’ must be true.”

“How so?” I asked.

“I live alone and cook for myself, and my favorite meal is pan fried steak,” he said. “I love it burnt on each side and rare in the middle.”

“So what?” I asked.

“Two years ago,” he said, “I had to have half of my stomach removed because of cancer”

Warning: Beware of rancid and over-cooked fats and oils.

Retired chiropractic doctor Frank Trapani’s background includes 41 years of practice plus doing investigative reporting and fitness programs for broadcast media in Hawaii. He lives in Walla Walla. For more information, go to drftrapani.com.


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