Americans have long been urged to embrace polyunsaturated fatty acid (PUFA) vegetable oils because they are low in saturated fats. These oils made from corn, peanuts, soybeans, safflower and sunflower seeds are high in omega-6 fatty acids, however. Their widespread use in processed foods such as crackers, condiments, chips, bread, coffee creamers, dips and plant-based processed meat alternatives means that many, if not most, Americans get a lot more omega-6 fatty acids in their diets than omega-3 oils. What’s the problem?
Omega-6 Oils and Cancer? Are Omega-3 Oils Safer?
New studies are connecting seed oils rich in omega-6 fatty acids with certain cancers. Last week we described a connection between these omega-6 PUFAs and colon cancer. This week we add to that story by sharing a study published in the Journal of Clinical Oncology (Dec. 13, 2024). It too points a finger at omega-6 fats. This time, though, the connection is with prostate cancer. More about that shortly.
Why would seed oils rich in omega-6 fatty acids be linked to colorectal or prostate cancer? And why would omega-3 oils be safer?
In a word, inflammation. Of course it is much more complicated than that. Please strap in for a short overview of fatty acid biochemistry. We know this is a tad challenging, but it could have a profound impact on your future health:
Essential Fatty Acids and Inflammatory Pathways:
The Difference Between Linoleic Acid (LA) and ⍺-linolenic acid (ALA):
This gets crazy complicated very fast, but please hang in for 2 minutes. I will do my best to keep it as simple as possible.
Linoleic acid (LA) is an omega-6 fatty acid. It is considered an “essential” fatty acid because the body cannot make it. We get it from food. Ditto for ⍺-linolenic acid (ALA). It too is an essential fatty acid. Unlike LA, however, ALA is an omega-3 fatty acid.
The Inflammatory Pathway:
The omega-6 fatty acid, linoleic acid (LA), is a precursor for arachidonic acid (AA). It is AA that creates pro-inflammatory compounds such as leukotrienes, prostaglandins and thromboxanes. This pro-inflammatory pathway facilitates the formation of mediators that help our innate immune system fight off pathogens. It is important to understand that inflammation is the body’s natural way to overcome infections and help us heal after injuries.
So, inflammation is good…in the short term and only up to a point. But when inflammation turns bad in the longer term, it can lead to a lot of mischief: cancer, arthritis, diabetes, atherosclerosis, allergies, asthma and many other chronic conditions.
The Anti-Inflammatory Pathway:
The omega-3 fatty acid, ⍺-Linolenic Acid (ALA), is a building block for eicosapentaenoic acid (EPA) and docosahexaenoic (DHA). This pathway leads to anti-inflammatory compounds such as protectins, lipoxins and resolvins. They help the body move from an attack mode to a healing process.
Compounds like EPA and DHA compete with AA (arachidonic acid) for similar enzymes. Think of it as an eating contest. There are piles of chips and guacamole.
One group of contestants is consuming lots more chips (loaded with omega-6 oils) than avocado-rich guacamole. The other group is gobbling down the guacamole (containing lots of omega-3 oils) with as few chips as possible. One group (the chip lovers) will have more pro-inflammatory omega-6 fatty acids in their bodies while the other group (the guac guzzlers) will be rich in anti-inflammatory omega-3 oils from avocados.
The bottom line is that there is a dynamic balance between attack and inflammation to deal with infection or danger. Once the initial battle is over, it is hopefully followed by healing and then recovery. We want to dampen down the initial inflammatory reaction.
Inflammation and Cancer:
Colorectal Cancer:
Researchers at the University of South Florida uncovered a possible consequence of continuous inflammation. They used sophisticated technology to analyze colorectal tumors.
Chronic inflammation linked to seed oil consumption showed up in the biomarkers they uncovered (Gut, Dec. 10, 2024). Utilizing fats with more monounsaturated and omega-3 fatty acids seems to help calm that inflammation. Fish, olive oil and avocados are all good sources of omega-3 oils. You can get the inside scoop on this research by reviewing our overview at this link.
Omega-6 Oils vs Omega-3 Oils and Prostate Cancer:
Another recently published study in the Journal of Clinical Oncology (Dec. 13, 2024) also suggests that a diet high in omega-6 fats could be harmful for men with prostate cancer on active surveillance. Substituting omega-3 oils through diet and fish oil supplements can slow cancer growth and delay the need for treatment.
The investigators tracked a biomarker called Ki-67 to determine the activity of the prostate cancer. They assigned 100 men with early-stage prostate cancer randomly to either their usual diet or a diet low in omega-6 fatty acids. That meant avoiding highly processed foods, fried foods, chips and baked goods. They also consumed more foods rich in omega-3 oils found in salmon and tuna. These volunteers also took fish oil capsules.
The goal was to decrease the ratio of omega-6 to omega-3 oils. Over the course of a year, the Ki-67 index dropped dramatically for the men on the low-inflammation diet.
The authors concluded that a diet low in omega-6 and high in omega 3 fats:
“…resulted in a significant reduction in prostate cancer tissue Ki-67 index, a biomarker for prostate cancer progression, metastasis and death.”
Nutrition Experts and Cardiologists Love Omega-6 Fats:
The nutrition establishment has been thrilled with omega-6 fats from cottonseed, sunflower, soybean, safflower, canola, corn and grapeseed oils for decades. They are inexpensive, have little if any taste and can be heated to a high temperature.
They are the go-to oils in most ultra-processed foods. Onion rings are fried in omega-6 fats. Ditto for fried chicken. Corn chips? Yup! High in omega-6 fats! That’s also true for potato and tortilla chips. Even tofu can be high in omega-6 fats.
Omega-6 PUFAs are supposed to be good for us because they have little, if any, saturated fat. They lower cholesterol and are supposed to improve cardiovascular health. When it comes to the question of inflammation, most of the cardiologists and nutrition experts insist that omega-6 fatty acids do not increase inflammation, but rather lower it.
Some nutrition experts even insist that these seed oils will lower the risk of cancer. I wonder what they think about the recent studies of colorectal and prostate cancer?
The Sydney Diet Heart Study (SDHS):
We wish the story were as simple as most of the experts maintain. They would like to ignore the Sydney Diet Heart Study.
That report concluded (BMJ Feb. 5, 2013):
“In this evaluation of data from the SDHS, selectively increasing the n-6 [omega 6] PUFA LA [linoleic acid] from safflower oil and safflower polyunsaturated margarine increased rates of death from cardiovascular disease, coronary heart disease, and all cause mortality compared with a control diet rich in SFA [saturated fatty acids] from animal fats and common margarines. This is the first published report to show an increase in mortality from cardiovascular disease and coronary heart disease, comparing this LA [linoleic acid] intervention to the control group, and demonstrating that the magnitude of increased n-6 LA intake was associated with higher risk of death.”
That was inconvenient. Most of the experts would prefer to ignore that study.
More Omega-3 Oils, Please!
For years, Americans were warned away from olive oil and nuts. Why? They are high monounsaturated fats. They also have some saturated fat, which is perceived as deadly for the heart.
Another ooops, though. The PREDIMED study compared a low-fat “heart healthy” diet to a high olive-oil and/or nut diet. The latter was high in omega-3 oils. The so-called heart-healthy diet was higher in omega-6 fats. The results were embarrassing (New England Journal of Medicine, June 21, 2018).
The envelope please:
“In this study involving persons at high cardiovascular risk, the incidence of major cardiovascular events was lower among those assigned to a Mediterranean diet supplemented with extra-virgin olive oil or nuts than among those assigned to a reduced-fat diet.”
You can read more about this research and the benefits of omega-3 oils at this link.
The Minnesota Coronary Experiment:
OK…I know you are getting tired of this. But there is one more study that deserves your attention. The nutrition establishment has tried mightily to ignore it. It was one of those randomized controlled trials that are rarely performed when it comes to food.
Roughly 9,000 patients were served food that was either high in omega-6 PUFA corn oil or high in saturated fat. The high-corn oil diet lowered cholesterol, but it did not improve survival (BMJ, April 12, 2016).
The conclusion:
“Available evidence from randomized controlled trials shows that replacement of saturated fat in the diet with linoleic acid effectively lowers serum cholesterol but does not support the hypothesis that this translates to a lower risk of death from coronary heart disease or all causes. Findings from the Minnesota Coronary Experiment add to growing evidence that incomplete publication has contributed to overestimation of the benefits of replacing saturated fat with vegetable oils rich in linoleic acid.”
Confused about linoleic acid (LA) vs. ⍺-linolenic acid (ALA)? Please scroll back to the top of this article for a 30 second refresher course.
Final Words on Omega-3 Oils:
We love extra virgin olive oil. We use it on salads, on bread and we cook with it for most things that require oil. Yes, it is more expensive than corn or safflower oil. But we are willing to spend more for omega-3 oils. We also cook with avocado oil. It is especially handy for high heat like stir frying.
Did you find this article of interest? If so, please share it with family and friends. We hope our discussion about linoleic acid and ⍺-linolenic acid was semi-understandable. If you have a slightly better understanding of the differences between omega-3 oils and omega-6 oils, you might want acquaintances to benefit as well. While you are at it, please encourage folks to sign up for our newsletter at this link. It helps us continue to bring you articles like this one. Thank you for supporting our work.
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