EPA, DHA, and ALA: What is the difference between these omega-3 fatty acids?

On labels and in articles about omega-3, you often come across three abbreviations: EPA, DHA, and ALA. They all belong to the omega-3 family, but they are not the same and are not interchangeable. They differ in structure, source, and especially in what your body does with them. DHA is primarily a structural fatty acid, EPA primarily a functional fatty acid, and ALA is the essential basic fatty acid.

Briefly summarized

The structure code indicates the number of carbon atoms and the number of double bonds. EPA, for example, has 20 carbon atoms and 5 double bonds.

What exactly are EPA, DHA, and ALA?

All omega-3 fatty acids have their first double bond on the third carbon atom, counted from the end of the fatty acid chain. That is where the name omega-3 comes from.

ALA is the shortest member of the family and comes from plant sources. It is also the only omega-3 fatty acid that is truly essential: your body lacks the enzymes to produce it itself, so it must come from your diet [1].

EPA and DHA are longer fatty acids. Although they are often mentioned together, they are two different fatty acids with their own roles. In principle, your body can produce them from ALA, but only to a limited extent (see further). EFSA recommends that adults consume 250 mg of EPA and DHA combined daily, and 0.5% of their daily energy intake for ALA [2].

Where do EPA and DHA occur?

EPA and DHA are found primarily in fatty fish such as salmon, mackerel, herring, and sardines, in shellfish, in fish oil, and in oil from microalgae. The composition varies by product, even within the same category.

Interesting detail: fish largely do not produce their own EPA and DHA. Microalgae produce these fatty acids, and they accumulate in fish via the food chain [3]. Oil from microalgae is therefore a direct source. DHA from algae oil is also absorbed just as well as DHA from salmon [4]. However, EPA from algae is still difficult to produce in high concentrations. Consequently, most algae oils contain mainly DHA and relatively little EPA. The label tells you how much of each.

Where does ALA occur?

ALA is found in plant sources. Flaxseed oil is the richest source: about half or more of the fatty acids is ALA. Chia seeds (about 18 g per 100 g), hemp seeds (about 10 g per 100 g), walnuts (about 9 g per 100 g) and rapeseed oil also provide ALA [1].

Important: foods containing ALA do not automatically contain EPA or DHA. Conversely, fish primarily provides EPA and DHA, and only small amounts of ALA.

Can your body convert ALA into EPA and DHA?

Yes, but only to a limited extent. Through a series of enzymatic steps, your body can first convert ALA to EPA and then to DHA. This conversion is not very efficient. Research with labeled fatty acids shows that in men, typically about 5 to 8% of ALA is converted to EPA, and usually less than 1% to DHA [5,7]. Women of reproductive age convert more efficiently, up to about 21% to EPA and 9% to DHA [6]. However, in them too, most of the ALA is burned as an energy source.

Conversion also depends on your diet. Omega-3 and omega-6 fatty acids use the same enzymes. A diet high in omega-6, such as linoleic acid from sunflower and corn oil, can therefore further inhibit the conversion of ALA [8]. The balance between omega-3 and omega-6 therefore deserves attention, both in the diet and in supplements [9].

Therefore, ALA on the one hand and EPA and DHA on the other are not interchangeable. Someone who consumes ALA does not automatically ingest the same amount of EPA and DHA.

What role do EPA, DHA, and ALA play in your body?

Because their structures differ, each of these fatty acids also has its own specific function. The most important distinction: DHA is primarily a structural fatty acid, while EPA is primarily a functional fatty acid. DHA contributes to the construction of the cell membranes of the brain and eyes. EPA is primarily a raw material for signaling molecules. ALA is the essential basic fatty acid from which both can be produced to a limited extent.

DHA: the structural fatty acid of the brain and eyes

DHA is the most important omega-3 fatty acid in the cell membranes of the brain and retina. The body carefully stores DHA in the brain [10]. In the rods of the retina, the cells that capture light, DHA can make up to half or more of all fatty acids [11]. Thanks to its long, extremely flexible chain, DHA keeps cell membranes supple. This suppleness plays a role in signal transmission between nerve cells and in the shape change of the light-sensitive protein rhodopsin when light falls on the retina [10,11].

In addition to this structural role, DHA is also the raw material for native signaling molecules, such as D-series resolvins , protectins , and maresins [12].

EPA: the functional fatty acid, raw material for signaling molecules

EPA is less of a building block and more of a functional raw material. In the brain, EPA is rapidly converted and broken down, so its concentration remains low [10]. Structurally, EPA is very similar to arachidonic acid, an omega-6 fatty acid. Both fatty acids compete for a place in cell membranes and for the same enzymes, which convert them into signaling molecules ( eicosanoids ) [12]. The signaling molecules formed from EPA are generally less potent than those formed from arachidonic acid. Additionally, EPA is the raw material for E-series resolvins [12].

Here you see again why the balance between omega 3 and omega 6 matters: which fatty acids are in your membranes helps determine which signaling molecules your body produces [9,12].

ALA: the essential basic fatty acid

ALA is the raw material from which your body can make EPA and DHA to a limited extent. However, most of the ALA is burned as an energy source, and some is incorporated into cell membranes [1].

What does Europe say? Recognized health claims

The European Union has recognized the following health claims for EPA and DHA, among others [13]:

How do you recognize them on the label?

"Omega 3" is an umbrella term. Therefore, check whether EPA and DHA are listed separately, preferably in milligrams per daily dose. In the case of vegetable oils such as flaxseed oil, "omega 3" refers almost entirely to ALA. With algae oil, you often find the designation "oil from microalgae," with or without the name of the algae, such as Schizochytrium. sp . This designation follows the European list of novel foods [14].

Frequently Asked Questions

What is the main difference between EPA, DHA, and ALA?

ALA is a plant-based and essential omega-3 fatty acid. EPA and DHA are longer fatty acids from fish and algae. Your body converts ALA into EPA only to a limited extent, and into DHA even less.

What does DHA do and what does EPA do?

DHA is primarily a structural fatty acid: a building block of the cell membranes in the brain and retina. EPA is primarily a functional fatty acid: a raw material for signaling molecules, in which it competes with the omega-6 fatty acid arachidonic acid.

Is EPA or DHA more important?

Both are important, but they have different roles. Because they are not interchangeable, it pays to check the label to see how much EPA and how much DHA a product contains separately.

Which foods contain EPA and DHA?

In fatty fish, shellfish, fish oil, and oil from microalgae. The composition varies by product.

Which plant-based foods contain ALA?

Flaxseed and flaxseed oil, chia seeds , hemp seeds, walnuts, and rapeseed oil. On the label, this is listed as "ALA" or "alpha-linolenic acid".

Can algae provide EPA and DHA?

Yes. Microalgae are the original source of EPA and DHA in the food chain. Most algae oils contain primarily DHA, because EPA from algae is still difficult to produce in high concentrations. The label tells you how much of each.

Why does the label sometimes only say "omega 3"?

Omega 3 is an umbrella term. Look at the separate listing of EPA, DHA, and ALA to know exactly what you are consuming.

References

1. Baker EJ, Miles EA, Burdge GC, Yaqoob P, Calder PC. Metabolism and functional effects of plant-derived omega-3 fatty acids in humans. Prog Lipid Res. 2016;64:30-56. doi:10.1016/j.plipres.2016.07.002

2. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on Dietary Reference Values for fats, including saturated fatty acids, polyunsaturated fatty acids, monounsaturated fatty acids, trans fatty acids, and cholesterol. EFSA J. 2010;8(3):1461. doi:10.2903/j.efsa.2010.1461

3. Gladyshev MI, Sushchik NN, Makhutova ON. Production of EPA and DHA in aquatic ecosystems and their transfer to the land. Prostaglandins Other Lipid Mediat. 2013;107:117-26. doi:10.1016/j.prostaglandins.2013.03.002

4. Arterburn LM, Oken HA, Bailey Hall E, Hamersley J, Kuratko CN, Hoffman JP. Algal-oil capsules and cooked salmon: nutritionally equivalent sources of docosahexaenoic acid. J Am Diet Assoc. 2008;108(7):1204-9. doi:10.1016/j.jada.2008.04.020

5. Burdge GC, Jones AE, Wootton SA. Eicosapentaenoic and docosapentaenoic acids are the principal products of alpha-linolenic acid metabolism in young men. Br J Nutr. 2002;88(4):355-63. doi:10.1079/BJN2002662

6. Burdge GC, Wootton SA. Conversion of alpha-linolenic acid to eicosapentaenoic, docosapentaenoic and docosahexaenoic acids in young women. Br J Nutr. 2002;88(4):411-20. doi:10.1079/BJN2002689

7. Plourde M, Cunnane SC. Extremely limited synthesis of long chain polyunsaturates in adults: implications for their dietary essentiality and use as supplements. Appl Physiol Nutr Metab. 2007;32(4):619-34. doi:10.1139/H07-034

8. Gerster H. Can adults adequately convert alpha-linolenic acid (18:3n-3) to eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3)? Int J Vitam Nutr Res. 1998;68(3):159-73.

9. D'Helft J, Caccialanza R, Derbyshire E, Maes M. Relevance of ω-6 GLA added to ω-3 PUFAs supplements for ADHD: a narrative review. Nutrients. 2022;14(16):3273. doi:10.3390/nu14163273

10. Dyall SC. Long-chain omega-3 fatty acids and the brain: a review of the independent and shared effects of EPA, DPA and DHA. Front Aging Neurosci. 2015;7:52. doi:10.3389/fnagi.2015.00052

11. SanGiovanni JP, Chew EY. The role of omega-3 long-chain polyunsaturated fatty acids in health and disease of the retina. Prog Retin Eye Res. 2005;24(1):87-138. doi:10.1016/j.preteyeres.2004.06.002

12. Calder PC. Omega-3 fatty acids and inflammatory processes : from molecules to man. Biochem Soc Trans. 2017;45(5):1105-15. doi:10.1042/BST20160474

13. Commission Regulation (EU) No 432/2012 of 16 May 2012 laying down a list of authorised health claims for food which do not refer to the reduction of disease risk or to the development and health of children. OJ L 136 of 25 May 2012, pp. 1-40.

14. Commission Implementing Regulation (EU) 2017/2470 of 20 December 2017 establishing the Union list of novel foods in accordance with Regulation (EU) 2015/2283. OJ L 351 of 30.12.2017, pp. 72-201.