Seed oils are vilified for the amount of omega 6 they contain. Seed oils are commonly called “industrial” seed oils, toxic, inflammatory, and touted to drive inflammation and chronic disease. And then of course we see influencers parading through supermarkets pointing to every food with the tiniest amount of seed oil and rant about avoiding it all costs.
So what does the evidence actually say about omega-6 fats, particularly linoleic acid, the main omega-6 fat in the diet? What about the other omega-6 fat arachidonic acid?
First, what is linoleic acid?
Linoleic acid (LA) is an essential omega-6 fatty acid. “Essential” means we must get it from food because the body cannot make it itself. It is found in foods such as:
- Nuts and seeds
- Sunflower, soybean, corn and safflower oils
- Many packaged foods made with these oils
- Smaller amounts in whole foods like eggs and poultry
For decades, linoleic acid has been studied in relation to cardiovascular disease, inflammation, and chronic disease risk.
Omega-6 has increased over the years
One of the reasons omega-6 has a bad reputation is that the amount in our diets has increased over the years, particularly in relation to omega-3. The primary reason is added oils are cheap, widely available and used in many processed foods. Along with the increase in omega-6 is the increase prevalence in many preventable diseases. This is an association, and does not necessarily mean seed oils are the cause. Many other changes in our diet and lifestyle have occurred.
This graph shows the change in the ratio of omega-6 to 3 over 80 years (source)
Sources: Chaves et al. 2019; Simopoulos 2002–2016; Sokoła-Wysoczańska et al. 2018; Molendi-Coste et al. 2011
The biggest confusion: “Omega-6 causes inflammation”
This idea comes from the fact that linoleic acid can be converted into arachidonic acid (ARA), which is used to make inflammatory signalling molecules called eicosanoids.
The concern goes like this: linoleic acid gets converted in the body to arachidonic acid (ARA), which produces pro-inflammatory compounds. More LA in the diet → more ARA → more inflammation → more chronic disease. Simple, logical, and largely unsupported by the human evidence.
The body tightly regulates this conversion, it is estimated at less than 1% of dietary LA is converted to ARA. Multiple studies have confirmed that eating more LA doesn’t meaningfully raise ARA levels in the blood or tissues. In real-world human studies, increasing linoleic acid intake does not consistently increase inflammatory markers.
A large systematic review of 30 randomised controlled trials looked at what happened to 11 different inflammatory markers, and found that higher linoleic acid intake did not significantly raise markers such as:
- C-reactive protein (CRP)
- IL-6
- TNF-alpha
- Fibrinogen
Some studies have even found that higher LA levels are associated with lower levels of pro-inflammatory markers.
What about heart disease?
This is where the evidence is strongest.
Higher linoleic acid intake is consistently associated with lower risk of cardiovascular disease and lower mortality rates.
One large meta-analysis involving more than 310,000 people found that higher intake of linoleic acid was associated with:
- 15% lower risk of coronary heart disease events
- 21% lower risk of coronary heart disease death
Replacing saturated fat with linoleic acid-rich foods appears to improve blood lipid markers, including LDL cholesterol and apolipoprotein B.
A separate analysis across more than 800,000 people found that higher LA intake was linked to a 13% lower risk of dying from any cause, including a 13% reduction in cardiovascular deaths and 11% reduction in cancer deaths. These aren’t small effects, and they hold up whether LA is measured by diet recall or by objective blood and tissue biomarkers.
Another concern – omega-6 competes with omega-3 for the same enzymes.
There is also a real concern about omega-6 competing with omega-3 fats for the same metabolic enzymes. In theory, high LA intake could reduce your conversion of plant-based omega-3s to the long-chain forms EPA and DHA. In practice, the conversion of plant omega-3s to EPA and DHA is already quite poor regardless of your LA intake, which is exactly why getting EPA and DHA directly from oily fish or a quality supplement is so important.
However low omega-3 intake with high omega-6 intake means that there may be an imbalance of these fatty acids in cell membranes where they get stored.
Ultra-processed foods muddy the waters
Many foods high in omega-6 fats are also ultra-processed foods:
- Deep fried takeaway foods
- Chips
- Fast food
- Packaged snack foods
People often blame the oil itself, when the problem may actually be the overall dietary pattern, excess calories, low fibre intake, lack of whole foods, or repeated high-temperature frying.
Are all omega-6 fats the same?
No – and this is an important nuance often missed online.
The term “omega-6” covers a whole family of fatty acids. Some appear beneficial, while others may behave differently. One genuinely interesting finding comes from a large German study that tracked individual omega-6 fatty acids separately. It found opposing effects: shorter-chain omega-6s like LA were associated with reduced mortality risk, while longer-chain omega-6s (like ARA) further down the metabolic pathway were associated with increased risk.
This is why broad statements like “omega-6 is inflammatory” are oversimplified.
My practical take as a nutritionist
- Adult Males (19-70+ years): 13 g/day to 17 g/day
- Adult Females (19-70+ years): 8 g/day to 12 g/day
The majority of omega-6 should come from whole foods (rather than added oils) such as:
- Nuts, seeds, nut butters, with smaller amounts of from quality vegetable and seed oils such as sesame seed oil
- Too many ultra-processed foods, and deep fried food
- Too little fibre
- Not enough seafood
- Low fruit and vegetable intake
- Excess calories
Limit the omega-6 fat arachidonic acid
Arachidonic acid is a long chain version of omega-6 and is a precursor to pro-inflammatory eicosanoid hormones. Because it directly makes the signalling molecules that increase inflammation, an excess amount of these in ratio to omega-3 in cell membranes appears to be pro-inflammatory. The dietary key is to:
- Eat plenty of omega 3 rich foods – seafood in particular (long chain omega-3). If you avoid seafood add omega-3 supplements from algae (vegan) or fish. Aim for 1-3 grams EPA+DHA per day.
- Avoid eating excessive amounts of ARA found in organ meats, egg yolks and fatty meats.
Check this earlier post for omega 6 and omega 3 amounts in many different foods: Omega 6 and 3 in nuts, oils, meat and fish. Tools to get it right.
