Their View: What’s the deal with seed oils?

I’m on vacation. So I have no idea why I decided to write on such a controversial topic this week. I would guess, though, that I’m not the only one scratching my head over the current banter against seed oils.

As you might guess, seed oils are liquid fats that come from plant seeds. The most notable are derived from canola, corn, cottonseed, soybean, sunflower, safflower, grapeseed and rice bran. Some media influencers have targeted these particular oils as being unhealthy. The issue seems to be how they are processed and the types of fats they contain.

There is quite a process to get oil out of seeds. And it’s more challenging than pressing the oil from the flesh of olives or avocados. A common solvent that manufacturers use to separate the liquid fat from the rest of the seed is a compound called hexane. It’s also used for the production of natural extracts, drugs and nutraceuticals, according to a 2022 article on this topic in the journal Foods.

Hexane can be toxic if inhaled as a gas. In fact, it’s a component of gasoline emissions. As a liquid solvent, however, it is evaporated off (without deteriorating nutrients) after doing its job to extract oil from seeds. Any trace amounts that may be present in seed oil has been determined to be “toxicologically insignificant” by the Department of Health and Human Services Agency for Toxic Substances and Disease Registry.

Seed oils are also high in monounsaturated and polyunsaturated fatty acids (aka MUFAs and PUFAs). Critics say seed oils are bad for us because they contain an excess amount of a certain omega-6 PUFA called linoleic acid.

However, omega-6 fat is one of two polyunsaturated fats — the other is the omega-3 alpha-linolenic acid (ALA) — that are “essential” for humans. That means we need them in our diets since our bodies cannot make these fats.

Strong evidence from clinical trials has shown that replacing some of the saturated fats in our diets (which is not essential by the way) with mono- or polyunsaturated fats helps our hearts and possibly lowers our risk for Type 2 diabetes.

So until we find solid evidence against seed oils, we might not want to throw the baby out with the bath water.

Instead of fixating on avoiding seed oils at all costs, we’d be better off to make reasonable decisions about the foods we choose to eat. Concentrate more on minimally processed foods — fruits, vegetables, lean protein foods, whole grains and dairy. I will continue to cook with canola and olive oils and not be afraid to use other products made with seed oils. You are free to make your own choices.

And we can all agree to continue to follow this subject. It pays to keep up with the science.

Barbara Quinn-Intermill is a registered dietitian and certified diabetes educator affiliated with Community Hospital of the Monterey Peninsula. She is the author of “Quinn-Essential Nutrition” (Westbow Press, 2015). Email her at to [email protected].