Polyunsaturated fats = healthy. Or, at least, that’s what we’ve consistently been told.
Countless health organizations — including the American Heart Association — recommend eating foods with unsaturated fat, especially polyunsaturated fats (let’s all agree to shorten it to PUFAs), instead of saturated fat when possible.
Why? Two words: heart health.
According to a 2015 Cochrane review, replacing foods rich in saturated fat with foods rich in PUFAs could lead to 27% fewer cardiovascular events.
So … what’s up with the widespread hate against PUFA-rich seed oils?
They’re called “toxic”, “inflammatory”, and “evil” — blamed for nearly every chronic health condition there is, from obesity to diabetes to depression (just search “seed oils” on TikTok or Reddit). So, let's get to the bottom of this head-scratching mystery together.
First things first. What are seed oils?
The term “seed oil” is somewhat of a misnomer.
While a few seed oils are derived from seeds, not all are. Instead, seed oil is an umbrella term for vegetable and seed oils. Here’s a list of the most common seed oils you’d likely find right in your kitchen pantry or on some of your favorite foods’ labels:
- (“True”) seed oils: Sunflower, cottonseed, safflower, canola, and grapeseed oil
- Vegetable oils: Soy, palm, and corn oil
Why are seed oils considered bad for you?
See, there are 2 types of PUFAs:
- Omega-3 fatty acids (considered anti-inflammatory)
- Omega-6 fatty acids (considered inflammatory)
And, as it turns out, seed oils are absolutely bursting at the seams with linoleic acid, a polyunsaturated omega-6 fatty acid.
The body's conversion of linoleic acid into arachidonic acid produces several inflammatory compounds, such as eicosanoids.
🫒 Olive oil: 3-21% linoleic acid, 55-83% oleic acid, and <1% linoleic acid (note: oleic and linoleic acid are omega-3 fatty acids)
🌻 Sunflower oil: 44-75% linoleic acid, 14-43% oleic acid
Soybean oil: 54% linoleic acid, 23% oleic acid, and 8% linoleic acid (side note: yep, couldn't find a soybean emoji)
So, the argument goes, "Since seed oils contain a higher ratio of omega-6 fatty acids than omega-3 fatty acids, they're pro-inflammatory — and, as we all know, inflammation is the root of all evil."
That statement is half-right.
Yes, inflammation is associated with many chronic diseases, including heart disease, type 2 diabetes, some types of cancer, arthritis, gastrointestinal disorders, and even Alzheimer’s.
But seed oils aren’t pro-inflammatory in the human body.
Wait … what? Didn’t we just say that the conversion of linoleic acid into arachidonic acid produces inflammatory compounds?
Here’s what research says about seed oils
As it turns out, many studies in healthy human adults have found that the increased intake of linoleic acid (or arachidonic acid, for that matter) does not increase the concentrations of many inflammatory markers.
And that epidemiological studies have even suggested that linoleic/arachidonic acid intake may be linked to reduced inflammation.
Honestly, the actual explanation is probably way too long — and complicated — for this article. So, just know that human physiology is extremely complex. Just because there's an increase in certain pro-inflammatory compounds doesn't mean that it'll translate to an actual rise in inflammatory markers in the body.
To quote the G.O.A.T Arnold Schwarzenegger in FUBAR (hi-five if you're binge-watching the series!): that's it, and that's all.
OK, that's not all (I just thought it seemed like a cool way to end the discussion 🤪).
Because while it’s difficult to explain the biochemical mechanism behind why omega-6 fatty acids aren’t inflammatory, finding evidence that linoleic acid is good for health isn’t.
What this means is: seed oils are not bad for you.
See for yourself:
2️⃣ 2023 review published in the International Journal of Molecular Sciences: Diets higher in linoleic acid and omega-6 fatty acids are associated with lower or similar:
Inflammation and oxidative stress levels, and
Risk of inflammation-related health conditions
3️⃣ 2021 review published in Obesity Review: The consumption of polyunsaturated fats — including linoleic acid — is associated with improvements in body composition (lower fat mass; increased lean mass).
Do not start guzzling seed oils
⚠️ Before you start drowning your foods with seed oils like you’re an Audi S8 at the gas station, note that the same basic principles about fat consumption apply:
- Eat fat in moderation (between 20 and 35% of total calories), with a relatively balanced mix of saturated, polyunsaturated, and monosaturated fat
- Minimize consumption of ultra-processed, hyper-palatable food products, such as pre-packaged cookies, biscuits, and chips; these are jampacked with trans-fat, which is considered the worst type of fat you could eat
There’s no shortcut to health
Cut out seed oils (or commonly demonized food group, like carbohydrates) from your diet, and you'll be healthy — a tempting notion, but it's also unhelpful.
In truth, there isn't one easy thing you could do that'll instantly make you healthier.
Instead, it’s the tiny, everyday habits that count:
- Prioritizing minimally processed foods and eating plenty of fruits, vegetables, legumes, nuts, seeds, whole grains, and fiber
- Eating enough protein for appetite regulation and lean muscle mass maintenance
- Staying physically active (hitting a good mix of cardio and resistance training)
And speaking of staying physically active … if you don’t know where to start with your fitness journey (especially in the gym), why not download GymStreak?
This smart, AI-powered personal trainer app tailors workout plans to your unique fitness goal, equipment accessibility, and ideal training frequency — so all you need to do is show up and work toward better health, 1 session at a time.
Bonus: you’ll also get access to a nutrition planner + tracker that’ll help you keep an eye on your calorie intake and macronutrient distribution (because you should keep your fat consumption <35% of total calories!)
Interested? Here’s a sneak peek of the app:
*sigh of relief* We'll guide you through it all — step-by-step. Just download the app, and you'll be making progress toward your dream body like never before.
Akkaya, M. R. (2018). Prediction of fatty acid composition of sunflower seeds by near-infrared reflectance spectroscopy. Journal of Food Science and Technology, 55(6), 2318–2325. https://doi.org/10.1007/s13197-018-3150-x
Hernández, M. L., Sicardo, M. D., Belaj, A., & Martínez-Rivas, J. M. (2021). The Oleic/Linoleic Acid Ratio in Olive (Olea europaea L.) Fruit Mesocarp Is Mainly Controlled by OeFAD2-2 and OeFAD2-5 Genes Together With the Different Specificity of Extraplastidial Acyltransferase Enzymes. Frontiers in Plant Science, 12. https://www.frontiersin.org/articles/10.3389/fpls.2021.653997
Hooper, L., Al-Khudairy, L., Abdelhamid, A. S., Rees, K., Brainard, J. S., Brown, T. J., Ajabnoor, S. M., O’Brien, A. T., Winstanley, L. E., Donaldson, D. H., Song, F., & Deane, K. H. (2018). Omega-6 fats for the primary and secondary prevention of cardiovascular disease. The Cochrane Database of Systematic Reviews, 7(7), CD011094. https://doi.org/10.1002/14651858.CD011094.pub3
Innes, J. K., & Calder, P. C. (2018). Omega-6 fatty acids and inflammation. Prostaglandins, Leukotrienes, and Essential Fatty Acids, 132, 41–48. https://doi.org/10.1016/j.plefa.2018.03.004
Liu, A. G., Ford, N. A., Hu, F. B., Zelman, K. M., Mozaffarian, D., & Kris-Etherton, P. M. (2017). A healthy approach to dietary fats: Understanding the science and taking action to reduce consumer confusion. Nutrition Journal, 16, 53. https://doi.org/10.1186/s12937-017-0271-4
Monnard, C. R., & Dulloo, A. G. (2021). Polyunsaturated fatty acids as modulators of fat mass and lean mass in human body composition regulation and cardiometabolic health. Obesity Reviews: An Official Journal of the International Association for the Study of Obesity, 22 Suppl 2, e13197. https://doi.org/10.1111/obr.13197
Poli, A., Agostoni, C., & Visioli, F. (2023). Dietary Fatty Acids and Inflammation: Focus on the n-6 Series. International Journal of Molecular Sciences, 24(5), 4567. https://doi.org/10.3390/ijms24054567
Schönbach, J.-K., Nusselder, W., & Lhachimi, S. K. (2019). Substituting polyunsaturated fat for saturated fat: A health impact assessment of a fat tax in seven European countries. PLoS ONE, 14(7), e0218464. https://doi.org/10.1371/journal.pone.0218464
Szpunar-Krok, E., & Wondołowska-Grabowska, A. (2022). Quality Evaluation Indices for Soybean Oil in Relation to Cultivar, Application of N Fertiliser and Seed Inoculation with Bradyrhizobium japonicum. Foods, 11(5), 762. https://doi.org/10.3390/foods11050762