RHR: Seed Oils and Colon Cancer

In this episode we discuss:

• What researchers actually found in the University of Florida study
• Why oxidation and processing are the real problems
• Whole food sources vs industrial seed oils
• What really matters when it comes to the omega-6 to omega-3 ratio
• The importance of avoiding obsession and social isolation
• Recommendations on which oils to use and those to avoid
• How you can improve your Omega-3 intake

Show notes:

• “Stability of avocado oil during heating: Comparative study to olive oil” by Berasategi, I., et al.
• “Importance of maintaining a low omega-6/omega-3 ratio for reducing inflammation” by DiNicolantonio, J. J., & O’Keefe, J. H.
• “Increase in adipose tissue linoleic acid of US adults in the last half century” by Guyenet, S. J., & Carlson, S. E.
• “Nut consumption and risk of cardiovascular disease” by Guasch-Ferré, M., et al.
• “Social relationships and mortality risk: A meta-analytic review” by Holt-Lunstad, J., Smith, T. B., & Layton, J. B.
• “Re-evaluation of the traditional diet-heart hypothesis: Analysis of recovered data from Minnesota Coronary Experiment (1968-73)” by Ramsden, C.E., et al.
• “The importance of the ratio of omega-6/omega-3 essential fatty acids” by Simopoulos, A.P.
• “The importance of maintaining a low omega-6/omega-3 ratio for reducing the risk of autoimmune diseases, asthma, and allergies” by DiNicolantonio, J.J. & O’Keefe, J.
• “Integration of lipidomics with targeted, single cell, and spatial transcriptomics defines an unresolved pro-inflammatory state in colon cancer” by Soundararajan, R., et al.
• “Impact of heating temperature and fatty acid type on the formation of lipid oxidation products during thermal processing” by Wang, Y., et al.
• “Mechanisms of the formation of nonvolatile and volatile oxidation products from methyl linoleic acid at high temperatures” by Yao, Y., et al.
• “An Update On Omega-6 PUFAs” by Kresser, C.
• Zero Acre Farm’s cultured oil
• Learn more about the Adapt Naturals Core Plus bundle, Bio-Avail Omega+, or take our quiz to see which products best suit your needs
• If you’d like to ask a question for Chris to answer in a future episode, submit it here
• Follow Chris on Twitter/X, Instagram, or Facebook

Hey everybody, Chris Kresser here. Welcome to another episode of Revolution Health Radio. If you spent any time on social media lately, you’ve probably seen a lot of chatter around seed oils. A study came out from the University of South Florida in late 2024 linking omega-6 fatty acids to colon cancer. And the internet did what the internet does best. It went absolutely bananas. You’ve got one side screaming that seed oils are poison and you should never, ever let a drop touch your lips, and then you’ve got the other side saying the fears are completely overblown and seed oils are perfectly fine. As usual, the truth is somewhere in the middle.

In this episode, we’re going to talk about what this study found, what it means for your health, and most importantly, how to think about seed oils in a practical, balanced way. Because here’s the thing. I’ve had patients who became so obsessed with avoiding seed oils that they stopped going out to eat with friends and family. They became socially isolated. And we know from research that social isolation is a much bigger predictor of early death than eating a little bit of seed oil at a restaurant. So by the end of this episode, you’ll understand the difference between naturally occurring omega-6 in whole foods like chicken and avocados versus the oxidized oils in ultra-processed and refined junk food. You’ll know which oils to keep in your kitchen and which to avoid, and you’ll walk away with a balanced, evidence-based perspective that lets you make informed choices without the fear and stress. Ready? Let’s dive in.

The University of Florida Study – What They Actually Found

So let’s start with the study that kicked off this whole recent firestorm. Researchers at the University of South Florida and Tampa General Hospital Cancer Institute analyzed 162 tumor samples from colon cancer patients. They used a mass spectrometer to measure the types of fats in and around these tumors. Nearly all of the lipid mediators in the tumors were in what’s called a pro-inflammatory class of fats. These are primarily omega-6 fatty acids, and these inflammatory lipids were suppressing the immune system around the tumor.

Here’s the crucial thing to understand. Dr. Timothy Yeatman, the lead researcher, was very clear in his interviews. He said, and I’m paraphrasing here, the study doesn’t show that seed oils cause cancer. What it shows is that ultra-processed foods with high amounts of omega-6 in the context of low omega-3 intake create chronic inflammation that may fuel tumor growth. The omega-6 to omega-3 ratio in these tumor environments was around 15 to 20 to one. That’s important. The colon tumors look like poorly healing wounds under the microscope. Cancer is basically a chronic wound that won’t heal, and when your body is living off daily ultra-processed foods, its ability to heal that wound decreases. The inflammation persists, the immune system gets suppressed, and that allows cancer cells to grow. So it’s not just about seed oils, it’s about the entire Western diet pattern. Ultra-processed foods, added sugars, oxidized fats, and a massive imbalance in omega-6 to omega-3 intake.

The Real Problem – Oxidation and Processing

Now let’s talk about why processing matters so much, because this is where a lot of the confusion comes in. Linoleic acid is an omega-6 fatty acid. It’s found naturally in chicken, nuts, seeds and, yes, in oils like sunflower and soybean oil. The question is, what happens to that linoleic acid? When linoleic acid is heated to high temperatures, especially repeatedly, it oxidizes. It forms what are called lipid oxidation products. Studies published in journals like the Journal of Agricultural and Food Chemistry have shown that when you heat oils rich in linoleic acid to temperatures like 180 degrees Celsius, which is a typical frying temperature, you get the formation of these oxidation products. They include compounds like 4-HNE and other volatile aldehydes that are potentially harmful to human health.

This is what happens in restaurant deep fryers and industrial food processing. The oil gets heated, it’s exposed to air and moisture, it degrades, and then it gets used again and again. In Europe, they actually have laws that prohibit reusing oil after it exceeds certain levels of these polar compounds. In the US, we have no such regulations. So when you’re eating fried food at a restaurant or ultra-processed foods from a package, you’re not just getting linoleic acid. You’re getting oxidized, degraded linoleic acid, and that’s a very different thing. Compare that to eating a piece of chicken with the skin on or a handful of walnuts or some avocado. Yes, these foods contain linoleic acid, but that linoleic acid hasn’t been subjected to repeated heating at 400 plus degrees. It’s in its natural form, and it’s packaged with protective nutrients like vitamin E, magnesium and polyphenols that help prevent oxidation.

The Omega-6 to Omega-3 Ratio – What Really Matters

For years, we talked a lot about the omega-6 to omega-3 ratio, and it was mentioned in the study as well. Research shows that humans evolved on a diet with a ratio of about four to one or less. Some estimates say it was closer to one to one. But today, the typical Western diet provides an omega-6 to omega-3 ratio of approximately 20 to one. Studies have shown that adipose tissue linoleic acid in the US has increased by 136 percent from 1959 to 2008. That’s a massive shift, and it happened in parallel with the rise in chronic inflammatory diseases.

But here’s where the science has gotten more nuanced. More recent research suggests that it’s not just about the ratio, it’s primarily about the denominator. In other words, omega-3 intake. A study published in Open Heart found that when you reduce the omega-6 to omega-3 ratio by increasing omega-3 intake, you see reductions in inflammatory markers like IL-6. What seems to matter most is having adequate omega-3s, particularly EPA and DHA from fish or fish oil, to resolve inflammation and balance out the omega-6. So if you’re eating adequate amounts of omega-3 fats, consuming some naturally occurring omega-6 in whole foods is unlikely to be a problem. That’s what the research suggests. The issue arises when you have a high intake of oxidized omega-6s from processed foods combined with inadequate omega-3 intake, as seen in the standard American diet. That’s when you get into trouble.

Context Matters – Natural vs. Processed Sources

This brings us to the most important distinction, and this is where I see people getting confused. Eating modest amounts of naturally occurring linoleic acid in the context of a healthy whole foods diet is very different from eating large amounts of oxidized linoleic acid from ultra processed food.

Let me give you some specific examples. Avocados contain linoleic acid. Avocado oil, which is mostly monounsaturated fat, has been shown in studies to have heat stability comparable to olive oil. Research published in the Journal of Food Science and Technology found that avocado oil remains relatively stable even when heated to cooking temperatures. Chicken with the skin on contains linoleic acid. Nuts and seeds contain linoleic acid. In fact, walnuts are very high in omega-6. But study after study shows that nut consumption is associated with reduced cardiovascular disease risk, reduced inflammation, and lower mortality. A pooled analysis of four prospective studies found that nut consumption resulted in a 37 percent reduction in cardiovascular related mortality. Now there’s a big caveat here. These are observational studies, so they don’t prove a causal relationship between nut consumption and cardiovascular disease. However, if we assume that linoleic acid in nuts increases the risk of heart disease, we would expect to see some relationship in these observational studies. And as we’ve just discussed, we not only don’t see a positive relationship, we see an inverse relationship, meaning people who consume more nuts tend to have lower rates of heart disease.

So clearly, the form and context matter. These whole foods come packaged with protective nutrients. They’re not subjected to industrial processing. They’re not repeatedly heated to extreme temperatures, and when you eat them as part of a diet that also includes adequate omega-3s, they are not going to cause problems. On the flip side, you’ve got french fries cooked in soybean oil that’s been sitting in a deep fryer for days. You’ve got packaged snack foods made with corn oil that’s been refined and deodorized using hexane. You’ve got ultra-processed frozen meals loaded with oxidized vegetable oils. That’s a completely different ball game.

A new study on omega-6 fats sent the internet into a seed-oil panic — but does it actually mean seed oils cause cancer? In this episode, we break down what the research really shows, why oxidized fats in ultra-processed foods are the real problem, and how to choose healthy cooking oils without falling into fear or obsessive eating habits. #RHRpodcast #seedoils #ChrisKresser

The Social Isolation Factor – Don’t Miss the Forest for the Trees

Now I want to address something concerning that I see happening in the health community. I’ve had patients come to me who are so terrified of seed oils that they won’t eat at restaurants anymore. They’ve stopped going to dinner parties. They’ve isolated themselves socially because they’re afraid of consuming even tiny amounts of seed oil. And here’s what I tell them: there’s a study that showed lack of social connection was a greater predictor of early death than body mass index, blood pressure, and even smoking 15 cigarettes a day. Let that sink in. Social isolation is more dangerous than smoking. So if you’re creating stress and anxiety for yourself, if you’re isolating from friends and family, if you’re obsessing over every molecule of linoleic acid that might cross your lips, you’re almost certainly doing more harm than good. The body is naturally resilient when we’re addressing the pillars of health – eating a nutrient-dense whole foods diet, getting adequate sleep, moving your body regularly, managing stress, spending time outdoors, and maintaining social connections. Stress and excessive or obsessive attention to diet at the expense of these other factors is counterproductive. It will have a bigger impact on your longevity than occasionally eating very small amounts of seed oils at a restaurant or a friend’s house.

The Research on Different Ratios

Let me share some specific research on what omega-6 to omega-3 ratios actually do in the body, because this helps put things in perspective. A paper published in Biomedicine and Pharmacotherapy by Dr. Artemis Simopoulos looked at different ratios and their effects on various conditions. They found that a ratio of two to three to one suppressed inflammation in patients with rheumatoid arthritis. A ratio of five to one had a beneficial effect for people with asthma, but a ratio of 10 to one had adverse consequences. The optimal ratio seems to vary depending on the disease and the individual, but clearly having a ratio of 15 to 20 to one, which is what’s typical in the Western diet, is not ideal. Studies published in several peer reviewed journals have shown that this high ratio creates a pro-inflammatory, pro-allergic, pro-thrombotic state. It perpetuates chronic low-grade inflammation, and that chronic inflammation is at the root of so many modern diseases. But again, the solution isn’t to become hysterical about every source of omega-6. It’s to reduce intake of oxidized omega-6 from processed and refined foods and increase intake of omega-3s from fish, fish oil, or if you are vegan, algae oil.

Practical Guidance – What Oils to Use

So let’s get practical. What oils should you keep in your kitchen? What should you use for cooking? I recommend focusing on solid fats and monounsaturated fats. For cooking at higher temperatures, use coconut oil, ghee, lard, or tallow from grass-fed sources. These have higher smoke points and are more stable when heated. Avocado oil is also excellent for high-heat cooking. It has good oxidative stability. I’m also a fan of Zero Acre Farm’s cultured oil, which is made from algae. It’s very high in monounsaturated fat. In fact, it’s almost 100 percent monounsaturated and has a smoke point of over 500 degrees. Their ghee and avocado oil products are great for cooking. For lower heat cooking and for drizzling on salads, olive oil is still my favorite. It’s been part of the Mediterranean diet for thousands of years, and we have abundant evidence for its health benefits. And it tastes great and there are many different artisanal options out there with different flavor profiles to enjoy.

What should you avoid? I’d stay away from soybean oil, corn oil, safflower oil, sunflower oil and cotton seed oil, especially in processed foods. These oils are typically refined using chemical solvents, they’ve often been heated during processing, and they’re the ones most likely to be oxidized before they even get to your kitchen. Now, does this mean you can never eat a french fry again? No, not, in my opinion, at least. It means you’re thoughtful about frequency. If you’re eating an overwhelmingly healthy, nutrient-dense, whole foods diet, going out to a restaurant occasionally and eating food cooked in seed oil is probably going to be fine. Having some chips at a party once in a while is probably fine. It almost certainly won’t have a significant impact on your long-term health or health span. The goal is not perfection. It’s reducing your intake of seed oils from highly processed and refined foods as much as is reasonably possible without causing social isolation or undue stress. 

The Omega-3 Solution

Here’s where I want to bring it back to something actionable, because reducing seed oil intake is only half the equation. You also need to ensure adequate intake of omega-3 fats, specifically EPA and DHA. These are found in cold-water fatty fish like salmon, mackerel, sardines, and anchovies. They’re also available in fish oil supplements and algae oil supplements if you don’t eat enough fish. If you need some extra support, check out Bio-Avail Omega+ from Adapt Naturals. It contains nearly one gram of EPA and DHA, the long chain omega-3 fats that we get from consuming fish, in addition to curcumin and black seed oil, which have metabolic, anti-inflammatory, and immune system benefits.

EPA and DHA are the omega-3s that have the most powerful anti-inflammatory effects. They help resolve inflammation. They compete with omega-6 fatty acids for the same enzymes. And when you have adequate EPA and DHA in your system, it effectively balances out the omega-6. In fact, the University of Florida researchers are now testing what they call resolution medicine. They’re using specialized derivatives of fish oil to address inflammation at its root cause in cancer patients. Early trials have shown some promise. This supports the idea that omega-3s are crucial for resolving the inflammatory state these tumors thrive in. If you’re eating a whole foods diet with some naturally occurring omega-6 but you’re also eating fatty fish two to three times a week, or taking a quality fish oil supplement like Bio-Avail Omega+, you’re in good shape. You don’t need to stress about the linoleic acid in your chicken or your handful of almonds.

All right, so let me recap what we’ve covered. The University of Florida study shows that ultra-processed foods high in omega-6 fats may contribute to chronic inflammation in colon tumors. But that’s not the same as saying that all seed oils or all omega-6 fats cause cancer. Context matters. Naturally occurring linoleic acid in whole foods like chicken, avocados, and nuts is very different from oxidized, repeatedly heated vegetable oils in processed junk food. The real issue is the combination of excessive omega-6 from processed food, inadequate omega-3 intake, and chronic unresolved inflammation.

The action steps are simple here. Focus on whole, unprocessed foods. Use stable cooking fats like coconut oil, ghee, avocado oil, and olive oil. Eat fatty fish regularly or supplement with quality fish oil. And don’t become so obsessed with avoiding seed oils that you create stress and social isolation in your life. There is no need to be obsessive about this. If you are addressing the pillars of health, eating a nutrient-dense diet, getting good sleep, moving your body, managing stress, spending time outdoors, and maintaining strong social connections, your body is naturally resilient. An occasional meal cooked in seed oil is not going to fully derail your health.

These are tools you can use to take control of your health without the fear and anxiety. Thanks for listening. You can find show notes and references at ChrisKresser.com. I’ll also put a link to an article I wrote called “An Update On Omega-6 PUFAs” in there as well, which goes deeper into this topic. Until next time, be well. Keep sending your questions to ChrisKresser.com/podcastquestion.