Seed oil or just rich in Omega 6?

According to the internet, the issue with seed oils is they contain high levels of omega-6 (fatty acids). The argument goes that one of the most common omega-6s — linoleic acid — is converted into arachidonic acid in your body. This, they suggest, leads to the formation of other compounds that increase levels of inflammation throughout the body. 

And that’s where the health warnings come in. A wide variety of conditions — from diabetes to depression and from cardiovascular disease to cancer — involve inflammation. So, if seed oils really do boost inflammation, that would be a worry. 

These concerns appeared decades ago, and in the last few years, their volume has intensified. However, you’ll be glad to hear that the latest research doesn’t back up this claim. Before we get cracking, let’s outline what linoleic acid is. 

What is linoleic acid?

Linoleic acid is an essential fatty acid. This means that your body needs it but can’t produce it. So, you need to get it through food. It's in seed oils, of course, but also in nuts, meats, and eggs.Linoleic acid plays a wide variety of roles in the body, including maintaining healthy skin and forming a part of your cell membranes. As we’ve learned, linoleic acid is converted into arachidonic acid, which is then converted into a wide range of other important compounds. These compounds are involved in lots of processes, such as wound healing, blood clotting, and regulating inflammation.   

Although inflammation is a dirty word — it’s associated with chronic diseases, after all — we should also remember that it’s an essential response to injury and infection. Our health would struggle without it. It's only when it's in the wrong place at the wrong time and in excess that it’s a problem. 

Recent omega-6 evidence 

Over the last few years, a number of reviews of human studies have failed to identify any health concerns linked to consuming linoleic acid in realistic doses. We’ll take a quick look at a few of these here. Firstly, a 2020 review concluded that higher levels of omega-6s, particularly linoleic acid, are linked to a reduced risk of cardiovascular disease.  

Similarly, they found that these fatty acids are associated with a reduced risk of developing metabolic diseases and type 2 diabetes. And they found that higher levels of linoleic acid are linked with better glucose control.   

Another review found that people who consume more linoleic acid or have more linoleic acid in their blood don’t have higher levels of inflammation. In fact, the authors explain that in many studies, participants consuming the most linoleic acid had the lowest levels of inflammation. They write that linoleic acid and arachidonic acid are involved in both pro- and anti-inflammatory pathways. And they don’t recommend for people to reduce their intake. 

One review looked at 15 studies on linoleic acid consumption and a range of markers for inflammation. Again, they found “virtually no evidence” that this compound increased inflammation. Scientists have shown that humans evolved consuming a diet where omega-3 and omega-6 were closer to a 1-to-1 ratio. Currently, though, most people consume much more omega-6 than omega-3 — around 16:1. This, some believe, increases inflammation because omega-3s are anti-inflammatory and omega-6s are pro-inflammatory. Below, we’ll give you a deep dive into the reasoning behind the ratio concerns. It’s a bit complicated, but it’s good to lay it all out. This way, when you see it explained elsewhere by seed-oil detractors, you’ll know what they’re going on about.    

The most common omega-3 in plant-based foods is alpha-linolenic acid (ALA). The most common omega-6 is linoleic acid, as we’ve seen. In your body, you have enzymes that break ALA into eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA and DHA are long-chain fatty acids, and they’re really important for health. You need those. The same enzymes that convert ALA into EPA and DHA also convert linoleic acid (the omega-6) into arachidonic acid, which we’ve already met. Arachidonic acid, EPA, and DHA all go on to form compounds called eicosanoids. The eicosanoids produced by EPA and DHA are anti-inflammatory, and the eicosanoids produced by arachidonic acid are slightly pro-inflammatory. The argument goes that ALA and linoleic acid “compete” for the enzymes. 

So, if you consume fewer omega-3s than omega-6s, the omega-6s hog the enzymes and, therefore, your body produces more of the slightly pro-inflammatory eicosanoids. In principle, that sounds reasonable. But does it stand up to real-world scrutiny? 

Testing the ratio hypothesis 

Some studies have looked at links between the ratio of omega-3 and -6 and inflammation. But, as far as inflammation is concerned, the ratio doesn’t seem to be too important. 

As long as you're consuming a reasonable amount of omega-3, the ratio doesn’t matter. A 2008 report on fats and fatty acids from the Food and Agriculture Organization of the United Nations concluded:

“Based on the evidence and conceptual limitation, there is no rational[e] for a specific recommendation for [omega-6 to omega-3] ratio.” 

For instance, one study involving more than 800 people found that omega-6 didn’t block omega-3’s anti-inflammatory action, but that people who had high levels of both had the lowest levels of inflammation. Another study with more than 1,100 participants found that higher levels of either omega-3s or -6s had lower levels of inflammatory compounds. 

Omega-6s and health 

Over the years, a number of large, well-conducted studies have found links between consuming omega-6s and positive health outcomes. For instance, a study in Finland recruited almost 2,500 men aged 42–60. They followed them for an average of 22.4 years. The scientists found that higher levels of linoleic acid in the blood were associated with a lower risk of death from cardiovascular disease and death from any cause. Levels of arachidonic acid had similar positive links, but they were less strong. Another study pooled data from 30 studies that came from 13 countries and almost 70,000 participants. The authors found that higher levels of linoleic acid were associated with a lower risk of cardiovascular disease, death from cardiovascular disease, and one type of stroke. 

Also, arachidonic acid levels weren’t associated with a higher risk of cardiovascular disease. In fact, individuals with the highest levels had a reduced risk. Another large study used data from more than 120,000 people. This time, the researchers focused on type 2 diabetes. They concluded that linoleic acid intake is associated with a lower risk of type 2 diabetes. 

"This myth that seed oils have trans fats is totally outdated.” 

It’s true that if you heat seed oils to a high temperature and reuse them repeatedly, toxic compounds can build up. However, this is only really relevant for restaurants and industrial deep fryers. And there are laws in place to protect the consumers in these cases. Importantly, when you’re frying an egg at home, this isn’t an issue. You won’t generally reach these high temperatures, and you won’t be reusing the oil.    

And here’s where some confusion can enter: A lot of ultra-processed foods contain seed oils. But they also contain high levels of sugar, salt, and other additives, while lacking fiber and other nutrients. So, eating a lot of ultra-processed foods that contain seed oils might well be linked to an increased risk of obesity and other conditions, but it’s not the seed oils that are to blame. 

What to do 

At the end of the day, if you want to avoid seed oils just in case, that’s fine. The evidence so far suggests that there are no issues with them, but everyone gets to choose.  

Citation ref: ZOE