Table of Contents
Omega-6 in Fresh Foods | The Problem: Rancid Oils | Impact of Repeatedly heated Oil | Unheated Vegetable Oils | Conclusions
Omega-6 is a type of polyunsaturated fatty acid (PUFA) that is essential to human health. In recent decades, however, consumption of omega-6 PUFAs has skyrocketed in developed countries (1), paralleling the dramatic increase in modern chronic disease. This has led many to vilify all forms of omega-6.
I wrote several articles on omega-6 years ago, including “How too much omega-6 and not enough omega-3 is making us sick” and “How much omega-3 is enough? That depends on omega-6.” Lots of new research has been published since then, and it’s important to constantly incorporate new information coming out in the medical literature. This article will thus serve as an update on my previous articles, this time focusing on the source of omega-6.
Omega-6 Is Not a Problem in Fresh, Whole Foods
Omega-6 has largely all been grouped together, regardless of the source. But whole-food sources of omega-6 also come packaged with other nutrients like dietary fiber (2), folic acid, niacin, tocopherols, vitamin B6, calcium, magnesium, potassium, phytosterols, polyphenols, vitamin E, and more. Some of these nutrients, like magnesium and vitamin E, have been shown to protect unstable omega-6 fatty acids from being oxidized (3).
Epidemiological evidence supports the idea that different sources of omega-6 might have different effects on health. Nuts and seeds contain large amounts of omega-6, yet are consistently negatively associated with cardiovascular disease (4). A pooled analysis of four prospective studies with follow-up time ranging from six to 18 years found that nut consumption resulted in a 37 percent reduction in cardiovascular-related mortality (5). Nut consumption has also been shown to reduce inflammation (6) and may also reduce risk of type 2 diabetes (7) and cancer (8).
Context does matter, though, and one situation where whole-food omega-6 could potentially become an issue is in people with low intake of omega-3 fatty acids (9). Short-chain omega-6 and omega-3 PUFAs directly compete for the desaturase and elongase enzymes that convert them to their long-chain derivatives. This means that excess omega-6 in the form of linoleic acid may inhibit the conversion of omega-3 alpha-linoleic acid into its long-chain derivatives, EPA and DHA (10). EPA and DHA are components of healthy cell membranes and are particularly important for cardiovascular and neurological health (11, 12). Luckily, as long as we eat adequate pre-formed EPA and DHA in the form of fatty fish, we effectively bypass this issue and can eat whole-food omega-6 without much tribulation.
Should you avoid whole foods high in omega-6?
What Is the Problem? Rancid Vegetable Oils.
The more concerning form of omega-6 is in vegetable oils. Repeated heating of vegetable oils is common practice in the food industry, particularly in large deep-fryers, because it significantly reduces the cost of food preparation. Instead of having to refill their deep-fryers with oil every day, many restaurants add just enough to top it off from the day before, only replacing the entire batch every few days or weeks.
In deep-fat frying, oil is heated to temperatures greater than 400 degrees Fahrenheit, while also being exposed to moisture and air. This causes thermal lipid oxidation, resulting in the formation of polar compounds and yielding new chemical functional groups that deposit in the cooking oil (13). Repeated heating also degrades the natural antioxidant vitamin E (14), which normally protects fatty acids against lipid oxidation.
Several European countries now have national food laws that prohibit reuse of an oil after it exceeds a certain polar compound content level (15). The U.S. has no such regulations (16). However, even the European laws overlook secondary oxidation compounds, which may also be harmful to human health and are not as well studied.
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The Effects of Repeatedly Heated Oil on Human Health
Repeatedly heated oil can also cause vascular inflammation and changes to vasculature that predispose to atherosclerosis (22). Studies have shown that oxidized LDL is much more important than total LDL level at determining atherosclerotic risk (23). Repeatedly heated oil has been shown to increase levels of oxidative stress in the body, including levels of oxidized LDL.
So if the problem is high heat, can unheated canola, soybean, or sunflower oil be a part of a healthy diet? To answer this question, we really need to understand how these oils are made.
What about Unheated Vegetable Oils?
There are three ways that oils are commonly extracted from their source:
- Rendering: this method uses heat only
- Chemicals: this method uses a solvent (usually hexane) and then subsequent heating to evaporate off the solvent
- Press it out: this method is purely mechanical. These oils are commonly labeled as “cold-pressed” or “expeller pressed.”
The majority of oils high in omega-6 PUFAs are produced using the second method. This means that even if you don’t heat your vegetable oil during cooking, it has likely already been heated long before it made its way to the supermarket. It may also have trace amounts of solvent remaining (24). After this extraction process, many oils are further refined, removing even more nutrients (25).
Given what we’ve learned, here are a few practical tips for modulating your omega-6 intake:
- Eat real food. Don’t fear the naturally occurring omega-6 in nuts, seeds, pastured meat, and other whole foods, especially if you are eating adequate amounts of omega-3 fatty acids. They are considered essential fatty acids, after all, so you do need some in your diet.
- Avoid industrial seed oils. Nix these nutrient-poor choices in favor of more nutritious and flavorful cooking fats like olive oil, coconut oil, ghee, and other pastured animal fats. Fats with higher saturated fatty acid content tend to have higher smoke points.
- Don’t go overboard with the nut flours. This sort of goes along with “eat real food.” While nut flours can be a great substitute for wheat flour in baked goods, they are easy to eat in large quantities, and the omega-6 fatty acids in these have the potential to be oxidized with heating. Switch it up with coconut flour or cassava flour.
- Eat pre-formed EPA and DHA. Consuming cold-water fatty fish is a good idea for everybody, but it’s especially important for people that have diets high in omega-6 fats.
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Excellent article. Ghee is a great option when you do not want the flavor of coconut oil in certain foods and you can get very large bottles of it in the Indian grocery store at a good price. Also recommend not buying oil in plastic bottles and always purchase cold pressed oils and keep out of heat and sunlight.
Winter Cohen MS,RD,CDN
I have an autoimmune condition and PUFAs trigger massive hair loss for me – including eyebrows and eyelashes. Even good quality cod liver oil and whole organic flax seeds and sesame seeds trigger hair loss which surprises me as I used to think it was just the oils and that they were perhaps rancid.
What about arachidonic acid? What is the relative risk of including “preformed omega-6” in the diet in ANY amount from things like egg yolks if you want to avoid excess inflammation?
So what about deep-frying in coconut oil? You can make some delicious plaintain or sweet potato chips that way. At <170 degrees, the boiling oil smells like nothing but water is coming out of it, but we do repeatedly re-head it. How would that compare to doing the same thing with a seed oil?
Maybe toss some concentrated vitamin E oil in there every time we re-heat…
The desaturase and elongase enzyme inhibition works both ways. Therefore, supplementing with EPA/DHA can inhibit the formation of gamma linoleic acid (GLA), an important anti-inflammatory omega-6 fatty acid. If using EPA/DHA supplementation to reduce inflammation, it is wise to also supplement with GLA.
I noticed no-one has mentioned palm oil. I buy the Nutiva red unrefined palm oil from Whole Foods. Is this a good oil to use for frying when you need a high smoke point?
I am involved with many natural doctors and Nutritional Therapists who are using a do-it-yourself blood test to test Fatty Acids.
The primary Indicators are:
Omega-3 Index >8% Is my Omega-3 high enough ?
Omega-6/3 Ratio 8% is relevant for heart health
Omega-6/3 Ratio is a very good indicator for Inflammation, especially for joints that are “on fire” such as early stage Rheumatoid Arthritis and also for early Endometriosis.
Most people have Omega-3 Index <2%, unless they are taking high strength fish oil or eating lots of oily fish
Many people have Omega-6-3 Ratio greater than 25:1 These people invariably have Inflammation and often have flaky skin and Depression and . . . and . . . . .
I have 3 Case Studies of 30-year old women with early stage Rheumatoid Arthritis who for 3 months took 3-5 mg of Omega-3 high strength natural fish oil each day – plus REDUCED their Omega-6 intake – and all the pain and symptoms went away. I was interested that all 3 called me a few months later and reported that their Endometriosis had also "gone away"
You can read more about this at:
http://www.omegametrix.eu ( scroll down for English )
http://www.expertomega3.com ( read the Studies )
http://www.greenvits.eu ( watch the videos & read the blogs )
Great update Chris! As for me… I never consume or cook with industrial seed oils. I’m that person who might pull a bottle of olive oil out of my purse at a restaurant. I do supplement fish oil because I am the only person in my home who likes to eat fish. I have not limited my consumption of nuts.
Hi, I usually cook with coconut oil, some ghee sometimes. I never use vegetable oils because of the GMO trash that is in them. I found the web site from.Dr Seralini, its address is gmoseralini.org there I saw what happens if you run the apprival tests for gmo for a longer period if time. It is just ugly. Take a look for yourself.
If I can use organic coconut oil instead of poisonous vegetable oils, there is no need to put my health at risc. Best price for coconut oil I find at Costco, a lot better than anywhere else.
You didn’t mention avocado oil. Would you please comment on this oil for occasional use in sautéing.
Are you not concerned at all about the FADH2:NADH ratio of fats? (And maybe there’s good reason not to be – just wondering.)
It seems like – particularly in a context where carbs are plentiful – having a low FADH2:NADH ratio (which omega-6 fats necessarily do) will be much more likely to cause overeating by lowering insulin resistance in cells?
How then do you now feel about ground flaxseed, Chris? Yay or nay? I did on the weekend used to like to have a flaxseed muffin-in-a-mug, but stopped because of the o6 issue. Could I resume the weekly muffin? Ty!
You seem to be unaware of the fact that the body is capable of transforming Omega-3 PUFAs into one another, so it’s not true that eating fish is ESSENTIAL. Flaxseed oil, for instance, is a great source that is vegetarian in nature. When it’s present in the diet of otherwise well-nourished people, it can be an ideal source of Omega-3 GENERALLY, as EPA and DHA can be created from that by enzymes created in the body (which are also necessary for absorption of those same PUFAs from fish!)
I’ll let someone more knowledgeable than I comment on the body’s ability to convert and use EPA and DHA in flaxseed oil (see, for example, https://chriskresser.com/why-fish-stomps-flax-as-a-source-of-omega-3/) , but flax has another concern. It is a phytoestrogen and that’s not necessarily desirable. This article http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3074428/describes both pros and cons of phytoestrogens and points out that despite benefits, phytoestrogens are, among other things, endocrine disrupters “with molecular and cellular properties similar to synthetic endocrine disruptors such as Bisphenol A (BPA).” There are safety concerns, particularly in the amounts one has to ingest to replace animal sources of essential fatty acids.
Ingesting flax caused me to have severe bleeding. I’ll stick to fish sources for my DPA/EHA, thank you very much.
Yet the conversion efficiency from the ALA in flaxseed oil and other plant sources to EPA and DHA is low. According to Wikipedia (with sources cited):
“Humans can convert short-chain omega-3 fatty acids to long-chain forms (EPA, DHA) with an efficiency below 5%. The omega-3 conversion efficiency is greater in women than in men, but less-studied. Higher ALA and DHA values found in plasma phospholipids of women may be due to the higher activity of desaturases, especially that of delta-6-desaturase.”
Moreover, the competition with omega-6 fatty acids may further decrease the extent of the conversion:
“These conversions occur competitively with omega-6 fatty acids, which are essential closely related chemical analogues that are derived from linoleic acid. They both utilize the same desaturase and elongase proteins in order to synthesize inflammatory regulatory proteins.”
Great article. The one question I have is: Is it OK to cook with unrefined,cold pressed oils with higher smoke points? – I’m from the UK where cold-pressed unrefined rapeseed oil is widely available. (Bright yellow – v different to typical canola oil). I don’t deep fry – but use it for igentle shallow frying. Will it still oxidise & become harmful?
I would recommend that rapeseed oil not be used extensively, as it is high in a toxic component, erucic acid, and certainly canola oil should be avoided entirely. Good quality oil is quite important, and organic, extra-virgin coconut, avocado and olive oil (and others) can be used with great benefit. Refined coconut oil has a higher smoke-point, but heat should generally be kept as low as possible to avoid auto-oxidation, allowing the healthier UNrefined coconut oil to take a greater role.
I use ghee for shallow frying which I find is very good for lack of smoke, even when camping – camp stoves have a very fierce heat.
Rapeseed oil does not have a good pedigree:
Excellent insight, Mr. Kresser.
Three questions of the board, and especially the author. First: O6 oils are quite prone to rancidity (just look at how often we encounter rancid oils in the best packaging possible: the nut or seed!) Yet we see that a processed seed oil, standing for months at room temperature out in the light in a clear plastic jug resists rancidity. How is this possible? What are these oils, in reality? Certainly they can’t still be O6. How could they be?
Second: “modified oil”. Anyone know what it is? I doubt the modification is an improvement. But I haven’t been able to find out what it is. Third: As Susan points out, virgin coconut oil is a very dominant flavor note. One my Redhead isn’t overly fond of, to boot. Certainly I’ll joyously throw it at any recipe with a little sweet, ginger, or warm N. African seasonings like harissa, or ras el hanout. But it can otherwise flat out ruin a recipe. How nutritionally inferior is the much-more-neutral refined form? Excellent content and fora, Mr. Kresser
I’m also curious about the refined vs non-refined coconut oil question. In addition to less flavor, the refined is also substantially cheaper at my market.
Same here… refined coconut oil allows for cooking at higher temps without fear of heating the oil past its “smoke point” and incurring the health issues that would result from doing so. I have been reading studies/reports that suggest that, for those on a budget, canola oil is an OK oil to use as long as it is non-GMO and expeller/cold-pressed. But the same issue arises with this oil as well – only the refined version can be used for higher temp cooking. Not everybody can afford these expensive fats (organic tallow/lard, duck fat, etc.) and oils (macadamia nut, pecan, etc.) to cook with.
So back to the main point of my reply – “How nutritionally inferior is the much-more-neutral refined form?” Is a refined coconut oil a better choice than a chemically produced, refined vegetable oil like soybean, corn, etc.? And if not, what type of non-refined, cold-pressed oil (or fat) is good for higher temp cooking that won’t break the bank?
“studies/reports that suggest that, for those on a budget, canola oil is an OK oil to use as long as it is non-GMO and expeller/cold-pressed” Again, back to my original query, how can it be? PUFAs are extremely prone to rancidity. If it’s standing in a jug in the light at room temp for months on end how can it be nutricious? How can it be O6 at all? I’m sure you can indeed get fresh cold-pressed canola, but I’ll bet it’s in a dark glass bottle, refrigerated, at a health food store. “budget” would not apply. If I’m mistaken, I throw myself at the mercy of the forum.
good point, natery… I must’ve just completely blanked out when reading that part of your post. I use avocado oil when I can, and it is usually in a dark colored glass bottle (or other non-clear container), but, most of all the other oils I have used in the past are in clear glass/plastic bottles. And, sadly, this is how most affordable oils are packaged.
But, again, even “virgin” avocado oil has only a medium-temp smoke point, along with “virgin” coconut oil. And forget about cooking with true pure virgin olive oil, it has such a low smoke point.
So, again, is a cold-pressed refined coconut oil/avocado oil/etc. a better choice than a chemically produced, refined vegetable oil like soybean, corn, etc.? And if not, what type of non-refined, cold-pressed oil (or fat) is good for higher temp cooking that won’t break the bank?
And, yes, I know that for healthier food, low and slow is the preferred cooking method, but there are times when a higher cooking temp is needed, and I would just like to find a healthy fat, or oil, that can withstand the heat (if one even exists).
“The best organic oils to safely use for cooking (the most heat tolerant) and their corresponding smoke point temperatures are:
• Avocado oil— 520 ° F
• Mustard oil— 489 ° F
• Ghee— 485 ° F
• Hazelnut oil— 430 ° F
• Grapeseed oil— 420 ° F
• Macadamia oil— 413 ° F
• Coconut oil— 350 ° F
• Butter— 350 ° F”
From Douillard, John. “Eat Wheat: A Scientific and Clinically-Proven Approach to Safely Bringing Wheat and Dairy Back into your Diet”
I liked the idea, mentioned by another reader, of buying ghee for cheap at an Indian grocery. I will try that myself.
On the recommendation of Chris Masterjohn, I use macadamia oil for making mayo and salad dressing. It is also excellent for sauteeing. It has a mild, buttery taste.
My guess is that the Omega 6s in nuts, while possibly not bad for human health, likely cause reduced weight loss or weight gain. Dr. Eades has a good article on this:
Otherwise, I agree with everything you’ve said.
I’ve also been using all kinds of animal fat for any kind of “frying” (meaning searing, mainly). I use bacon fat, home-made lard, home-made beef tallow, duck fat, goose fat, etc. Our home-made lard is great for searing meat after it comes out of a sous vide machine, for instance. I’ve even used our lard to fry plantains in, as a treat. We’ve also found some places that sell tallow from grass-fed cows, nicely made lard, etc.
I do use extra virgin olive oil or avocado oil for home-made mayo or salads. That’s about it in terms of vegetable oils (other than coconut oil, that is).
I’ve found the Eades’ article interesting…We could say, that most nuts are also rich in antinutrients…
Nevertheless, we also have African tribes that heavily rely on mongongo nuts…
It’s a bit controversial issue, probably some nuts are better than the others, as macadamia nuts for example
African tribes have a completely different microbiome than western civilizations. One cannot compare their diet with ours but it’s clear that they eat a lot more healthily since they’re still hunter gatherers.
I certainly agree with most of the stuff about microbiome, but I don’t want to go so far to overlook our genome. Now it seems that it’s all about microbiome and we are forgetting what we actually are aside from that.
It’s about the interaction between everything, not just about one thing, and it’s proven by the fact that survivor men that had to live in the jungle for years seemed to be perfectly adapted to live their despite their western provenience and microbiome.
It takes some good sense overall…the microbiome stuff is being overexploited by big pharma and from those who want to make you believe that it’s not possible to be healthy outside of our crazy little world.
You can actually compare our diets…
Yes I did shy away from nuts and seeds high in omega 6, especially because I do not eat fish or meat. I do not eat oils high in omega 6, but prefer olive oil or coconut fat. This is an interesting development and an argument I have not heard before, thank you for posting the article. I am more inclined not to worry about almonds and peanut butter now.
Almonds are very high in oxalate, so there are other choices that are better, like hemp or pumpkin seeds.
I often use avocado oil in cooking, especially at higher heats like baking/roasting chicken or vegetables, especially when I don’t want even a trace of coconut flavor (Nature’s Way liquid coconut oil is great, but sometimes I don’t want even a hint of that flavor). It has a very neutral flavor. I don’t fry, but for other stovetop cooking I usually use pastured ghee, butter, sometimes olive, coconut or avocado oil. For salad dressing I like olive, sometimes a specialty seed or nut oil like macadamia, or I’ll just use a mashed up avocado as my “oil” in a creamy dressing. I’d rather have a quarter avocado than 1-2 T of oil.
When I say “it has a very neutral flavor” I mean avocado oil.
You didn’t mention avocado oil. Would you please comment on this oil for occasional use in sautéing.
Thank you Chris, for this clarification. This is great to know. Yes, I have been conscious about eating too many nuts and seeds because of the omega 6 content. But now I can relax a little, since I don’t eat processed foods. And I very rarely cook with fats – I mostly cook in water and then add fat if I want it. In the rare instances I do cook with fat, it’s ghee or coconut oil. Also, I’m not crazy about how so many Paleo people use almond flour for baking.
Great discussion, I have found that eating a diversity of organic nuts and seeds in our daily regimen has helped to stabilize as our family has become a grain free, sugar free, and ketogenic for various health related issues. I often questioned how to gauge the omega 3 and omega 6 and we take a good quality fish oil with over 3 grams of EPA and DHA combined. I now feel less consumed with worrying about one or two servings of say, a pancake made with almond flour, coconut flour, grinded pumpkin seeds, sunflower seeds and brazil nuts all raw and organic. These are delicious and easy to make. Also, a similar combination can be used to make a “nutty flour” to coat organic chicken with an organic egg wash. The heat in cooking is medium low and 350 F. (pancakes, and baked chicken).
The nutrients can boost a comprised autoimmune hypothyroidism issue. Thanks for the update, and valuable input.
No need for almond flour for pancakes. Try a combo of coconut flour , potato starch,arrowroot powder, pysillium husk,a clean grass fed plain unsweetened whey protein powder