Omega-3 Fish Oil: What the Research Shows About EPA and DHA

TL;DR

• Omega-3s are fats your body can't make. The three main forms are EPA, DHA, and ALA.
• DHA is authorised in the EU to support normal brain function, and EPA and DHA together to support normal heart function, at defined daily amounts.
• The body converts very little plant based ALA into EPA and DHA, so fish or fish oil is a more direct source.
• The omega-3 index and your triglycerides are the clearest blood signals of your status.

What omega-3 fatty acids are

Omega-3 fatty acids are a family of polyunsaturated fats your body can't produce on its own. The three main forms are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA). EPA and DHA come mainly from oily fish and fish oil. ALA comes from plants like flaxseed and walnuts, but the body converts very little of it. Brenna et al. (2009) reviewed the conversion data and found that less than 5 percent of dietary ALA reaches EPA, and under 0.5 percent reaches DHA, in adults on a typical Western diet.

DHA is a structural part of brain and retina tissue. EPA feeds into the body's signalling molecules that regulate inflammation. Most clinical research focuses on these two forms.

Under EU Regulation 432/2012, DHA is authorised to contribute to normal brain function and normal vision at 250mg per day, and EPA and DHA together are authorised to contribute to normal heart function at 250mg per day combined.

What research has looked at

What follows is context on the research base, not a set of claims about outcomes for you.

Eslick et al. (2009) pooled 47 randomised trials and reported that omega-3 supplementation lowered triglycerides by an average of around 14 percent, with a small rise in HDL. Triglyceride response is one of the most consistent findings across omega-3 trials.

Bhatt et al. (REDUCE-IT, New England Journal of Medicine, 2019) studied high dose EPA in adults with raised triglycerides who were already on statin therapy. Researchers have studied cardiovascular outcomes in that specific high risk group. Read this as background on the research base rather than a claim about what a supplement will do for you.

Yurko-Mauro et al. (2010) studied DHA and measures of memory in older adults with age related cognitive decline. Senftleber et al. (2017) reviewed 42 trials on marine oil and joint symptoms. If you have specific health concerns, talk to your doctor before changing anything.

Blood markers that indicate a need

Triglycerides are the most accessible signal. Fasting triglycerides above 1.7 mmol/L are considered borderline raised in Dutch practice.

The omega-3 index, the percentage of EPA and DHA in red blood cell membranes, is a direct measure of long term status. Harris and Von Schacky (2004) described an index below 4 percent as less favourable and above 8 percent as the target range. A high omega-6 to omega-3 ratio on a full fatty acid panel, common in Western diets, also points to low omega-3 intake.

Genetics and omega-3 metabolism

The FADS1 and FADS2 genes build the enzymes that convert short chain precursors into EPA and DHA. Glaser et al. (2011) found that reduced function variants convert ALA at a fraction of the already low average rate, which makes plant sources effectively inadequate for those carriers.

The APOE gene influences lipid metabolism. Minihane et al. (2000) reported that APOE4 carriers showed a smaller triglyceride response to fish oil than APOE3 carriers. These variants help explain why the same dose lands differently across people.

What we see at Get Body Data

At Get Body Data, we see wide variation in omega-3 index even among people who eat fish regularly. For someone whose FADS variants point to poor conversion, relying on flaxseed isn't a workable plan, and preformed EPA and DHA from fish oil is the sensible route. We set the dose against your triglycerides, your omega-3 index, and your FADS and APOE variants rather than a fixed number.

Frequently asked questions

Can I get enough omega-3 from flaxseed?

For many people, no. Conversion of plant based ALA to EPA and DHA is low, and lower still for people with reduced function FADS variants. Oily fish or fish oil provides EPA and DHA directly.

How much EPA and DHA should I take?

The authorised amounts for the EU claims are 250mg per day for the relevant functions. The right total for you depends on your blood markers and goals, which is a conversation to have with a clinician.

Fish oil or algae oil?

Algae oil provides DHA (and some products EPA) from a plant source, which suits people who avoid fish. Both can raise your omega-3 index. The choice comes down to preference, form, and dose.

Does fish oil need to be taken with food?

Taking it with a meal that contains some fat can help absorption and reduces the chance of fishy aftertaste. Timing is otherwise flexible.

Disclaimer

This article is for information only. It isn't medical advice. Statements about the role of EPA and DHA in the body refer to authorised health claims under EU Regulation 432/2012. Research citations describe the scientific literature and are not claims about outcomes for individual readers. Always talk to your doctor before starting or changing a supplement plan.

References

Bhatt DL, Steg PG, Miller M, et al. Cardiovascular risk reduction with icosapent ethyl for hypertriglyceridemia (REDUCE-IT). New England Journal of Medicine. 2019;380(1):11-22.

Brenna JT, Salem N, Sinclair AJ, Cunnane SC. Alpha-linolenic acid supplementation and conversion to n-3 long-chain polyunsaturated fatty acids in humans. Prostaglandins, Leukotrienes and Essential Fatty Acids. 2009;80(2-3):85-91.

Eslick GD, Howe PR, Smith C, Priest R, Bensoussan A. Benefits of fish oil supplementation in hyperlipidemia: a systematic review and meta-analysis. International Journal of Cardiology. 2009;136(1):4-16.

Glaser C, Heinrich J, Koletzko B. Role of FADS1 and FADS2 polymorphisms in polyunsaturated fatty acid metabolism. Metabolism. 2011;60(12):1697-1703.

Harris WS, Von Schacky C. The Omega-3 Index: a new risk factor for death from coronary heart disease? Preventive Medicine. 2004;39(1):212-220.

Minihane AM, Khan S, Leigh-Firbank EC, et al. ApoE polymorphism and fish oil supplementation in subjects with an atherogenic lipoprotein phenotype. Arteriosclerosis, Thrombosis, and Vascular Biology. 2000;20(8):1990-1997.

Senftleber NK, Nielsen SM, Andersen JR, et al. Marine oil supplements for arthritis pain: a systematic review and meta-analysis. Nutrients. 2017;9(1):42.

Yurko-Mauro K, McCarthy D, Rom D, et al. Beneficial effects of docosahexaenoic acid on cognition in age-related cognitive decline. Alzheimer's and Dementia. 2010;6(6):456-464.