When it comes to omega-3s, DHA often takes centre stage. It is present in the brain. In the retina. It supports the baby's development even before birth.
Yet there is another, much more discreet molecule alongside it: EPA.
It gets less attention. Yet it has a completely different role.
What exactly is EPA?
EPA stands for eicosapentaenoic acid. Like DHA, it belongs to the long-chain omega-3 family.
Our body can produce some of its EPA from ALA, the essential omega-3 found in walnuts, flaxseed, and certain vegetable oils. In the omega-3 metabolic pathway, EPA thus appears before DHA: ALA → EPA → DHA.
However, considering it solely as an intermediate step would mean missing the point: EPA has its own biological functions.
To understand the whole family and this conversion in more detail, read our article What exactly are omega-3s?
Concretely, how does this role differ from that of DHA?
DHA is particularly present in certain membranes, especially those of the brain and retina, where it plays a structural role. EPA, on the other hand, is more frequently renewed and transformed there, and can serve as a precursor to different signalling molecules.
It could almost be summarised as follows: DHA contributes greatly to structure; EPA contributes more to messages. This image is deliberately simplified, but it helps explain why two such similar omega-3s can have different roles.
Why do we talk so much about EPA for the heart?
DHA builds structure. EPA carries messages. We have just seen this. Yet in the heart, this boundary blurs: this is where EPA is most studied today — always alongside DHA.
EPA + DHA: a duo for heart function
EPA and DHA contribute to the normal function of the heart. The beneficial effect is obtained with a daily intake of 250 mg of EPA and DHA.
It is important to understand that this benchmark concerns their combined action. These two omega-3s do not behave exactly the same way in the body, but together they contribute to the balance of several mechanisms involved in cardiovascular function.
Oily fish naturally provide these two fatty acids in varying proportions. This is also what explains why, in our diet, they are very often found together rather than considered separately.
And what about triglycerides?
EPA and DHA are also studied at higher intakes for their action on certain blood lipid parameters, starting with triglycerides. From a daily intake of 2 g of EPA + DHA, they contribute to the maintenance of normal blood triglyceride levels.
Triglycerides are fats that circulate in our blood and notably constitute a form of energy transport and storage. Their concentration depends on many factors, including diet, metabolism, and the way the liver produces and uses lipids.
When they are present in excessive amounts in the blood, we speak of hypertriglyceridaemia. In the long term, high concentrations are associated with an increased cardiovascular risk and, when they become very high, can also increase the risk of pancreatitis. At these intake levels, EPA and DHA can be involved in the regulation of some of these mechanisms, especially at the level of hepatic lipid metabolism.
We must therefore distinguish common nutritional intakes from the higher quantities used to act on certain parameters of lipid metabolism.
Is EPA really "anti-inflammatory"?
We often hear this expression when talking about omega-3s. As with DHA, the biological reality is however more interesting than a simple switch capable of "turning off" inflammation.
EPA can be transformed into different biologically active molecules. It is involved in the production of certain eicosanoids, a large family of lipid messengers involved in inflammatory, vascular, or immune responses. Its presence can thus change the balance of the molecules produced from the different fatty acids present in our membranes.
EPA shares certain enzymatic pathways with arachidonic acid (ARA), an omega-6 also used to make eicosanoids. When the relative availability of these fatty acids changes, the profile of the mediators produced can also evolve. It is therefore not a matter of simply opposing "bad omega-6" and "good omega-3", but of understanding that several families of fatty acids together feed a real library of lipid signals.
In other words, EPA does not simply "extinguish" inflammation: it provides another raw material to the machinery that makes some of our lipid signals.
The story does not stop at eicosanoids.
EPA can also serve as a precursor to specialised pro-resolving mediators, or SPMs. Among them are series E resolvins. These molecules intervene in the phase where the body must organise the end of an inflammatory response: limit the excessive arrival of new inflammatory cells, promote the removal of debris, and gradually guide the tissue back to balance.
As with the mediators derived from DHA, we can imagine them as conductors of the return to calm.
This is why the term "pro-resolving" sometimes describes this biology better than the simple word "anti-inflammatory".
Where do we naturally find EPA?
EPA is almost always associated with fish. Yet its story begins long before fish.
Oily fish: the best-known sources
Sardines, mackerel, herring, anchovies, or salmon naturally provide EPA and DHA.
However, the quantities and especially the EPA/DHA ratio vary greatly depending on the species, its diet, its origin, or even the season.
This is one of the reasons why French dietary recommendations remain simple: two portions of fish per week, one of which is oily fish.
And microalgae?
As with DHA, certain aquatic microorganisms are capable of producing EPA.
Several microalgae, notably certain species of Nannochloropsis or Phaeodactylum, are naturally rich in EPA and are the subject of extensive work to develop new sources of this omega-3 without going through fish.
However, these pathways are still largely at the development stage for human food in Europe. To date, EPA-rich oils from these microalgae do not have the same authorisations and commercial maturity as the DHA-rich algal oils already present on the European market.
The potential is nevertheless real: strain selection, improvement of cultivation yields, extraction, and purification are the subject of major research work.
Not all microalgae therefore produce the same omega-3s: some are particularly interesting for DHA, while others could open new pathways for EPA production tomorrow.
To discover how these oils are really obtained and how their production differs from that of fish oils, discover our article How are fish and microalgae oils produced?
How much EPA should you consume?
EPA has an interesting particularity here compared to DHA.
ANSES sets a recommended dietary intake of 250 mg of EPA per day for adults.
This nutritional benchmark should not be confused with the threshold of 250 mg of combined EPA + DHA seen above for the "normal heart function" claim: the first is a recommended intake by nutrient, the second a minimum quantity justifying a claim on a finished product. Two distinct regulatory logics, not to be added together without caution.
EPA or DHA: do you really have to choose?
Probably not.
DHA occupies a remarkable place in the structure of certain tissues. EPA is more involved in the production and balance of different signalling molecules.
They also work together, especially when it comes to the normal functioning of the heart.
Two molecules from the same family, but two different ways of participating in the functioning of our body.
And perhaps this is precisely the great lesson of this series: talking about "omega-3s" in the singular masks a much more fascinating biological diversity.
ALA opens the way. EPA carries messages. DHA integrates deeply into some of our membranes.
One family, several molecules, several stories.
To continue our exploration: