Over recent decades, researchers have hypothesized that the ratio of omega-6 to 3 intake in the human diet may contribute to chronic disease risk.
However, current evidence suggests that the dietary omega-6 to 3 ratio itself likely isn’t the issue. In fact, a critical appraisal even noted that the omega-6 to 3 ratio “has become scientifically outdated” as far back as 2018.
This article discusses the omega-6 to 3 ratio in the human diet and the most important considerations surrounding the topic.
If you have six apples and one orange, the ratio of apples to oranges is six to one (or 6:1).
Likewise, the same rules apply when calculating the omega-6 to 3 ratio. If you consume 10 grams of omega-6 and 0.5 grams of omega-3, then that ratio will be 20:1. In other words: the omega-6 to 3 ratio refers to the amount of omega-6 we consume compared to omega-3.
Both of these fats have different functions within the body:
Omega-6: The main dietary form of omega-6 fatty acid (linoleic acid) is a precursor to arachidonic acid, which plays a role in pro-inflammatory and anti-inflammatory processes. As a precursor, it can convert to arachidonic acid in the body.
The Omega-6 to Omega-3 Ratio Has Significantly Changed
According to some researchers, humans evolved on a diet that provided omega-6 and omega-3 at a relative ratio of around 1:1. However, estimates based on current dietary trends now place this ratio anywhere between 15 to 1 and 20 to 1.
The reason for much of this change is how humans eat. As people have started to eat less seafood and fewer whole foods, omega-3 intake has fallen. Also, our intake of omega-6 has risen rapidly, mainly due to vegetable oil intake.
This is because most ‘vegetable’ oils are made from the concentrated oil extracted from nuts and seeds, which are high in the primary form of omega-6 found in foods: linoleic acid.
In 1909: Soybean oil, which is primarily a source of omega-6 fat, contributed 0.006% of calories in the average American diet.
By 1999: Soybean oil now provided more than 7% of total calories in the average diet. Notably, these figures indicate a 1000-fold increase in consumption.
Some people argue that these changes to the dietary intake ratio of omega-6 to omega-3 may have negative connotations for human health. We will examine the legitimacy of such claims by analysing what the current scientific research demonstrates.
EPA + DHA proportion: The amount of the omega-3 fatty acids EPA and DHA in the blood (as a percentage of total fatty acids).
AA/EPA ratio: These tests may also show the ratio of AA to EPA in the blood.
For those unaware of any of these abbreviations, the list below explains what they mean:
EPA: Eicosapentaenoic acid (EPA) is one of two highly bioavailable forms of omega-3 found in seafood.
DHA: Docosahexaenoic acid (DHA) is the other highly bioavailable omega-3 found in seafood. Both these fats are “preformed,” which means they are a form of omega-3 ready to use by the body.
AA: Arachidonic acid (AA) is an omega-6 fatty acid produced in the body from linoleic acid, the primary form of omega-6 found in foods like nuts, seeds, and vegetable oils. Small amounts of preformed arachidonic acid are also present in some animal-based foods like eggs and salmon.
Potential Benefits of Increasing Dietary EPA/DHA Intake
Here’s a quick summary of some of the recent research findings on the potential benefits of increasing EPA and DHA intake.
An updated 2025 review of mechanisms and clinical outcomes assessed the evidence on EPA and DHA intake and cardiovascular health. The review found that higher intakes (and blood levels) of EPA and DHA are linked to reduced cardiovascular risk.
A 2018 systematic review of randomized controlled trials demonstrated that higher intake of EPA and DHA improved several risk markers for cardiovascular disease. These improvements included lower triglycerides, larger LDL particle size, and higher HDL levels. Additionally, larger intakes of EPA alone lowered LDL levels.
While higher intakes of EPA and DHA may support cardiovascular health, it is important to note that adverse effects may be possible at very high intake levels.
For example, the 2025 review of clinical outcomes found that high-dose supplementation can potentially increase the risk of atrial fibrillation (abnormal heart rhythm).
For this reason, it is important to consult with a healthcare provider before considering any diet or supplementation regime for individualized guidance.
Is a High Dietary Omega-6 To Omega-3 Ratio Bad?
Now that we have established the potential benefits of a higher omega-3 index, we will assess whether the relative amounts of omega-6 and omega-3 in the diet is important. Specifically, whether a high dietary omega-6 to omega-3 ratio negatively influences the omega-3 index.
First, as discussed, higher blood levels of omega-3 to omega-6 (e.g. the ratio of EPA to AA) are thought to be beneficial. Studies in this area have shown that lower EPA/AA ratios are associated with an increased cardiovascular disease risk.
However, evidence suggests that the absolute amount of omega-6 compared to omega-3 in the diet is probably not the main issue. Instead, the issue appears to be more about a low intake of preformed omega-3.
Let’s now look at some reasons why.
Competition for Uptake: Omega-6 and Omega-3
You may have heard that dietary omega-3 and omega-6 compete for uptake and absorption in the body; this is somewhat true.
However, this applies to the plant-based form of omega-3, which is known as alpha-linolenic acid (ALA):
Conversion is required: Unlike when we consume preformed EPA and DHA in seafood, the body must convert ALA into EPA and DHA.
Uptake competition:ALA competes with linoleic acid (LA), the plant-based form of omega-6, for conversion into EPA and DHA. This means consuming relatively large amounts of linoleic acid can lower the amount of ALA that can be converted into EPA and DHA.
Randomized trial: A 2026 randomized controlled trial tested what happens when participants consume a high amount of linoleic acid (10% of total calories) or low (2%) for 12 weeks. The high LA intake group had lower blood levels of EPA relative to arachidonic acid at the end of the trial.
Doesn’t apply to EPA and DHA: A key factor to understand is that higher intake of linoleic acid doesn’t adversely affect blood levels of omega-3 when people consume EPA and DHA. This is because these preformed forms of omega-3 can be directly incorporated into the body’s cells and do not have to compete for conversion.
Why Sufficient EPA/DHA Intake Matters Most
Increasing dietary intake of preformed omega-3 (EPA/DHA) has several effects:
As this shows, a sufficient intake of omega-3 from EPA and DHA has a much stronger impact on blood levels of omega-3 than the relative amounts of omega-6 and omega-3 in the diet.
Most People Consume Low Levels of EPA and DHA
Although we have established that EPA and DHA intake is the most important factor for blood levels of omega-3, many people have a low intake.
Although certain regions, such as Japan and Scandinavia, had high blood levels of EPA and DHA, most of the world did not. In Japan, the percentage of EPA and DHA as a fraction of total fatty acids was very high (>8%). Yet, it was very low (<4%) in the Americas, Europe, the Middle East, Southeast Asia, and Africa.
One of the key reasons for this low intake is the lack of dietary omega-3 from seafood sources. For instance, data from the National Health and Nutrition Examination Survey (NHANES) showed that U.S. adults only consumed a median 0.07 ounces (2g) of oily fish per day.
How to Increase EPA and DHA Intake
The best and most reliable way to get more EPA and DHA from food is to increase oily fish consumption.
That said, while EPA and DHA intake is more impactful than total omega-3 (ALA) intake, all foods that contain ALA do still contribute. Here are the richest food sources of total omega-3.
Fish oil or algae supplements that provide EPA and DHA are also good options for those that don’t like fish.
Considerations For Vegans and Vegetarians
It can be difficult to find sources of EPA and DHA on a vegan diet.
However, microalgae supplements (known as algal oil) are a vegan-friendly source of preformed EPA and DHA. As with fish oil supplements, look for a product that contains high levels of EPA and DHA.
It is worth noting that past research has shown that the actual amount of EPA and DHA in omega-3 supplements can be significantly less than the label claims. As with all supplements, this makes choosing a reputable brand important.
The website Labdoor, which we have no affiliation with, keeps a listing of well-rated fish oil and vegan omega-3 supplements. These ratings include test analyses looking at whether the supplement’s fatty acid content meets their label claims, so it is a good way of checking a specific supplement.
Is Omega-6 Inflammatory?
One of the main reasons you may have heard the omega-6 to omega-3 ratio mentioned is the claim that omega-6 fatty acids are inherently inflammatory. However, this claim is overly simplistic and lacks a nuanced understanding of how omega-6 fatty acids interact with the body.
The original argument that omega-6 fatty acids are inflammatory largely stems from the following research findings:
AA makes pro-inflammatory compounds: AA is a key “ingredient” used by the body to make eicosanoids, which are chemicals that help regulate inflammation. Using aspirin can block the conversion of AA into these pro-inflammatory eicosanoids.
EPA and AA competition: The omega-3 eicosapentaenoic acid (EPA) and AA compete with each other as materials that can activate specific enzymes to regulate inflammation, either through an anti-inflammatory or pro-inflammatory effect.
Precursor competition for uptake: Alpha linolenic acid (ALA), the form of omega-3 found in plants, and linoleic acid, also compete with each other to be converted into EPA or AA, respectively.
In other words, claims about the omega-6 to 3 dietary ratio are often influenced by the idea that “good” anti-inflammatory omega-3 and “bad” pro-inflammatory omega-6 are in constant competition. However, this is an overly simplistic (and incorrect) view. Inflammation isn’t always bad, and neither is omega-6.
Dietary Omega-6 Is Not Inherently Inflammatory
Arachidonic acid can be converted into a range of molecules that play a role in inflammatory processes. While some of these are pro-inflammatory, others have anti-inflammatory functions.
Furthermore, the amount of EPA/DHA to AA in the cells influences inflammatory processes rather than the relative net amounts of omega-6 to omega-3 consumed in food.
Also, a systematic review of human trials demonstrated that high intakes of linoleic acid as part of typical Western diets does not significantly raise tissue levels of arachidonic acid.
Further research has looked into whether dietary omega-6 is inflammatory, finding:
A systematic review of fifteen randomized controlled trials found a lack of evidence to support the idea that increased dietary linoleic acid intake leads to increased inflammatory markers.
Blood markers of inflammation were not significantly affected by increased linoleic acid intake in a systematic review and meta-analysis of more than 30 clinical human trials.
In a systematic review and meta-analysis of observational trials involving more than 310,000 participants, greater linoleic acid intake was associated with a reduced risk of coronary heart disease in a dose-response manner.
Summary
As covered in this article, here is a summary of the main take-home points:
Omega-3 fatty acids are essential, and we need to obtain them from our diet.
EPA and DHA, the preformed omega-3 fatty acids found in seafood, contribute to blood levels of EPA and DHA significantly more than the plant form of omega-3 called ALA. This is because ALA requires conversion to EPA and DHA, which happens at only low rates.
The tissue ratio of omega-3 (EPA/DHA) to arachidonic acid (AA) is important, but the exact ratio of omega-6 to omega-3 in the diet is less important.
The dietary ratio of omega-6 to omega-3 does have some influence on blood ratios of omega-6 and 3, and these effects are more significant when the only dietary source of omega-3 is ALA.
The evidence from recent scientific research shows that absolute intake of preformed omega-3 (EPA and DHA) plays a much more significant role than the dietary intake ratio of omega-6 to 3.
There is a lack of significant evidence for linoleic acid being inflammatory or significantly increasing tissue omega-6 levels, especially alongside the dietary intake of EPA and DHA.
Michael works as a nutritionist in a community setting and holds a Master's degree in Clinical Nutrition. He is a Registered Associate Nutritionist (ANutr) with the Association for Nutrition (AfN), and has published peer-reviewed research.
