Well, here at kenkco HQ, we don’t believe in fearmongering furor. So we hunkered down with one of our in-house Registered Dietitians, Joana Mendonça, to set the seed oil story straight. *Spoiler alert* seed oils are not the monsters you may think they are!

Let’s start by chewing the fat (pun intended)…

“To understand this topic better, we first need to talk about fats. All oils contain fats, of which there are two kinds: saturated fats and unsaturated fats. Most oils contain both types of fat in different proportions, but are likely to have a higher amount of one or the other.

Saturated fats 

• Often come from animal sources, including meat and dairy products, but can also be found in some plant foods, such as coconut oil. 

• Eating too much saturated fat has been associated with an increase in “bad” cholesterol (LDL), which increases the risk of heart disease.

Unsaturated fats 

• Mainly found in plant based foods, such as nuts, seeds, olives and avocados. 

• These are broadly considered to be beneficial, as several studies have shown that they can help improve blood cholesterol levels and exert an overall positive impact on human health. 

• Unsaturated fats can be further divided into two groups: monounsaturated fats (e.g. omega-9, found in olive oil) and polyunsaturated fats. Some important functions are attributed to polyunsaturated fats, which have a unique subgroup that you've probably heard of, called essential fatty acids. These are your omega-3s and omega-6s, both of which cannot be synthesized by the body and, like vitamins, need to be supplied by food.”

Aren’t seed oils a source of unsaturated fats?

“Yes! Many vegetable oils, and seed oils in particular, are rich in unsaturated fats (“good” fats) and low in saturated fats. However, in most seed oils, omega-6 is predominant. And omega-6 is one of the main reasons why some people suggest avoiding seed oils.”

So what’s the issue with omega-6?

“One of the most common omega-6s is a compound called linoleic acid. Linoleic acid is converted into arachidonic acid in the body, which some people claim sets the stage for chronic inflammation. If this were true, it would be worrying… since a wide range of diseases such as diabetes, cardiovascular disease and cancer are associated with inflammation. However, the latest research suggests otherwise.

A 2019 meta-analysis, which included 30 studies, on the association of linoleic acid (LA) and arachidonic acid (AA) with incident cardiovascular disease, showed that higher levels of LA and possibly AA had a lower risk of major cardiovascular events. 

Research from 2020 also concluded that higher levels of omega-6, in particular linoleic acid, were associated with a reduced risk of cardiovascular disease. 

Another study published in the American Journal of Clinical Nutrition in 2018, which followed about 2,500 men for 22 years, found that those with the highest blood levels of linoleic acid had a 43% lower risk of dying from any disease during the study period. 

These studies suggests that linoleic acid might, in fact, play a role in cardiovascular disease prevention. In addition, linoleic acid performs a wide variety of functions in the body, including maintaining healthy skin and forming part of cell membranes.”

So why do seed oils get a bad rep?

“It’s true that many of the foods we see available on the market today that contain seed oils are considered to be unhealthy. But are the seed oils really the cause? Many of the foods that include seed oils are ultra-processed – think packaged snacks, chips, crackers, salad dressings and pre-prepared meals. These tend to be higher in sodium, sugar, saturated fats, as well as additives to improve taste, texture, appearance and shelf life. And they often contain lower levels of dietary fiber and micronutrients.

Increasing evidence suggests that high consumption of ultra-processed foods is associated with a rise in non-communicable diseases, such as cardiovascular diseases, cancer, diabetes and obesity. It is therefore better to moderate your consumption of these foods. But the seed oils themselves do not appear to be to blame for the associated health issues.”

What about cooking with seed oils?

“When heated beyond a certain limit (what we call thermal oxidation), the characteristics of seed oils can change and produce potentially harmful substances and free radicals. Excessive production of free radicals, with an overload of the cell's antioxidant defense system, results in oxidative stress, which can be worrying. Nevertheless, cooking with seed oils at home shouldn't be a problem as long as you store and use them properly. If you avoid reusing them and repeatedly heating them to high temperatures, you will avoid the potentially harmful effects of thermal oxidation.”

All in all…

“It shouldn’t be a problem to include seed oils in your diet—as long as you focus on eating less processed foods and have an overall healthy and varied diet, with organic, natural ingredients as far as possible. Use seed oils to cook with, in place of butter or coconut oil, which are sources of saturated fats.

Overall, seeds are friends not foe. Like nuts, they are highly nutrient-dense foods, rich in unsaturated fats, proteins, and fibers. They are also good sources of vitamins, minerals and antioxidants. Chia seeds, for example, are composed of different functional components including fiber, polyphenols, omega‐3 fatty acids, vitamins and minerals such as magnesium and potassium. Pumpkin seeds are densely packed with useful nutrients such as amino acids, vitamin E, zinc, potassium, unsaturated fatty acids as well as phytosterols and phenolic compounds.”

So there you have it. Don’t believe the haters, kids! And definitely don’t believe everything you read or watch on the internet about nutrition, unless its come from a veritable source!

Joana Mendonça is one of kencko's Registered Dietitians. She has a BSc in Dietetics and Nutrition from the Lisbon School of Health Technology and a keen interest in food sustainability and vegetarianism. She is also a proud cat mom.