A walnut, a sardine, a few flaxseeds, fish oil or microalgae oil. Very different foods, but one word keeps coming up: omega-3.
Yet, behind this name lie several molecules. One comes mainly from the plant world. Another has its own roles in the body. The third is found even in our brain and retina.
ALA, EPA, DHA: three molecules from the same family, related to each other, but far from identical.
Why are they all called "omega-3"?
"Omega-3" is first and foremost a family name. These polyunsaturated fatty acids have a particular shape, with several small "kinks" along their molecule. The number 3 simply indicates where the first of these kinks appears, starting from one end. In the case of omega-3s, the first kink is in the third position from this end; for omega-6s, it is in the sixth position, and for omega-9s, in the ninth position.
There is no need to go any further into chemistry to understand the essentials. Saying "omega-3" is a bit like saying "fruit": an apple and a mango belong to the same family, without being identical or providing us with exactly the same things.
It is the same for omega-3s. In nutrition, three names mainly come up: ALA, EPA and DHA. And each deserves its own profile.
ALA: the one our body cannot make
ALA, or alpha-linolenic acid—the "little" omega-3 of the family, the one from which it all begins—has a fundamental peculiarity: our body cannot make it. It must therefore come from our diet, notably from walnuts, flaxseeds or certain vegetable oils: it is said to be essential.
This idea seems obvious to us today. Yet, a century ago, scientists did not even know yet that certain fatty acids were essential.
In the 1920s, by studying what happened when almost all fats were removed from the diet, researchers thought they had discovered a new factor close to a vitamin. They even temporarily dubbed it "vitamin F". They later understood that it was not a vitamin, but fatty acids: ALA is one of them.
And it does not only serve as a starting point for other omega-3s. It has its own nutritional benefit, notably at the cardiovascular level: ALA contributes to the maintenance of normal blood cholesterol levels (beneficial effect obtained with a daily intake of 2 g of ALA).
EPA: a marine omega-3 with its own story
EPA, or eicosapentaenoic acid, takes us further towards the marine world. It is found notably in oily fish and, more broadly, in the marine food chain.
Our body can use EPA to make small molecules, resolvins, which participate in coordinating certain biological responses. Among them are mediators studied in the resolution of inflammation, that is, the mechanisms that accompany the gradual return to balance after an inflammatory reaction.
It is also credited with a well-established nutritional benefit when it acts with DHA: EPA and DHA contribute to the normal function of the heart (beneficial effect obtained with a daily intake of 250 mg of EPA and DHA).
EPA is therefore not just an intermediate on the way to DHA: it has its own functions.
To learn more, discover our article EPA: what are its benefits and where can it be found?
DHA: a special place in the brain and vision
DHA, or docosahexaenoic acid, is the "big" omega-3 of nutritional interest in the family. It comes at the end of the omega-3 chain. It is particularly present in the membranes of the brain and the retina.
It should not be imagined as a "booster" that would suddenly give more memory or better vision. Its role is more structural: it is part of the structure of highly specialised tissues, all the way down to the cells that allow us to process information or capture light.
This presence corresponds to recognised nutritional benefits: DHA contributes to maintenance of normal brain function and to the maintenance of normal vision (beneficial effect obtained with a daily intake of 250 mg of DHA).
DHA also plays a special role during the development of the foetus and the child, which explains why it is so often mentioned during pregnancy and the first years of life. This subject deserves to be explored on its own, however.
Discover it in our article DHA: benefits, sources and dosage of this omega-3.
Looking for DHA without fish oil? Our microalgae-derived DHA omega-3 supplement provides 250 mg per plant-based capsule—the daily intake at which DHA contributes to the maintenance of normal brain function and normal vision.
Can our body really convert ALA into EPA and DHA?
Now that we know the three molecules better, one question becomes almost inevitable: if ALA can serve as a starting point for the other omega-3s, could a handful of walnuts actually replace a sardine after all?
Our body does have the enzymes necessary to gradually convert ALA. Very simply:
ALA → EPA → DHA
But the journey is far from perfectly efficient. In humans, the conversion of ALA to EPA is possible but low, while the continuation to DHA is virtually non-existent and variable.
ALA is classed as essential in the strict sense because our body cannot make it. EPA and DHA, by contrast, are described as conditionally essential: the body can in theory make them from ALA, but in practice only in very small amounts.
This is why ALA-rich plant foods and foods that directly provide EPA and DHA are not two perfectly equivalent paths.
A walnut and a sardine can both contribute to our omega-3 intake. They simply do not provide us with the same molecules.
So, which is the best omega-3?
Probably none.
Looking for a winner among ALA, EPA and DHA is like forgetting what makes them interesting in the first place.
ALA is essential and comes mainly from the plant world. EPA has its own functions and acts notably with DHA for the heart. DHA, meanwhile, has a separate role in the brain and the retina.
The best option remains to seek a balance in the consumption of each of them.
So one word — omega-3 — covers several different things. And that may be the most useful thing to remember: the next time you see "omega-3" on a food or a supplement, do not just look at the quantity.
First ask yourself: which omega-3 are we talking about?