What are omega-3 fatty acids – and why are they essential?

Omega-3 fatty acids are polyunsaturated fatty acids that the human body cannot produce in sufficient quantities on its own. Three forms are particularly relevant to health: alpha-linolenic acid (ALA), which comes primarily from plant sources such as linseed or rapeseed oil, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are found mainly in fatty marine fish and algae. Although the body can convert ALA into EPA and DHA to a limited extent, the conversion rate is estimated to be well below 10%. Therefore, those who do not regularly eat fatty fish often do not meet their EPA and DHA requirements through plant-based omega-3 sources alone.

DHA is a structural component of cell membranes, particularly in the brain and the retina of the eye, where it accounts for a significant portion of polyunsaturated fatty acids. EPA is primarily involved in the regulation of inflammatory processes, acting among other things as a precursor for inflammation-resolving messengers (resolvins, protectins).

What does the EFSA officially say about omega-3?

Unlike many dietary supplements, the evidence for omega-3 is exceptionally well documented: the European Food Safety Authority (EFSA) has officially approved several health claims for EPA and DHA, each with a specific minimum quantity required for the claim to apply. This precision is important, as many marketing texts omit these thresholds, creating the impression that any dose is sufficient for every stated effect.

→ Source: EFSA NDA Panel, Scientific Opinion on Health Claims Related to DHA, EPA and Brain, Eye, Heart, Triglycerides and Blood Pressure, EFSA Journal 9(4):2078 (2011)

Heart health: What studies really show – including the atrial fibrillation question

Omega-3 fatty acids have been considered heart-healthy fats for decades, and the EFSA claim regarding normal heart function is scientifically recognized. At the same time, the picture has become more nuanced in recent years, and an honest presentation should show both sides.

On the benefit side is the REDUCE-IT study led by Deepak Bhatt, in which a high-dose, prescription form of EPA (4 g of icosapent ethyl daily) reduced the risk of major cardiovascular events in high-risk cardiovascular patients. However, this same study provided an important safety signal: under high-dose EPA therapy, atrial fibrillation or flutter occurred in 5.3% of participants, compared to 3.9% in the placebo group. This connection is now openly discussed on relevant medical portals, but rarely appears in marketing texts for omega-3 supplements.

→ Source: Bhatt, D. L. et al. (REDUCE-IT Investigators), Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia, New England Journal of Medicine 380(1):11-22 (2019)

For practice, this means: the 250–300 mg of EPA+DHA per day mentioned in the DGE everyday recommendation is well below the 4 g daily dose at which this increased risk was observed in the REDUCE-IT study. Those who take high-dose omega-3 (several grams daily) for medical reasons or have a history of atrial fibrillation should have this medically monitored instead of self-administering high doses.

Brain, mood, and cognitive health

DHA is a structural component of nerve cell membranes, and the EFSA claim regarding normal brain function is based on this role. When questioning whether omega-3 can also actively improve mood or prevent cognitive decline, it is worth looking at two different research questions in a nuanced way.

Mood and depression: A meta-analysis by Liao et al., which evaluated 26 randomized controlled trials with approximately 2,160 participants, found an overall favorable effect of omega-3 PUFAs on depressive symptoms. It is worth taking a closer look at the ratio of EPA to DHA: an older but frequently cited meta-analysis by Sublette, Ellis, Geant, and Mann, which evaluated 15 randomized controlled trials with 916 participants, showed a statistically significant reduction in depression severity specifically in EPA-dominant supplements (EPA share ≥ 60% of total dose), while DHA alone showed no corresponding effect. Those who wish to use omega-3 specifically for depressive symptoms should discuss this with a doctor rather than viewing it as a standalone treatment.

→ Source: Liao, Y. et al., Efficacy of Omega-3 PUFAs in Depression: A Meta-Analysis, Translational Psychiatry 9:190 (2019); Sublette, M. E., Ellis, S. P., Geant, A. L. & Mann, J. J., Meta-Analysis of the Effects of Eicosapentaenoic Acid (EPA) in Clinical Trials in Depression, Journal of Clinical Psychiatry (2011)

Cognitive decline and dementia: Here, a contrast emerges between observational data and controlled studies. A 2023 meta-analysis published in the American Journal of Clinical Nutrition by Wei, Li, Dong, Tan, Xu, and colleagues, which included 48 longitudinal studies with over 100,000 participants, found an association between higher omega-3 intake and a lower risk of cognitive decline. The large-scale, randomized controlled VITAL study, evaluated by Kang et al. in over 3,500 older adults, however, found no significant difference in cognitive decline between the omega-3 group (1 g of marine n-3 fatty acids daily) and the placebo group over 2 to 3 years. The most likely reason for this difference: observational studies often capture long-term dietary habits, whereas a supplement study in already older participants may start too late to generate a measurable difference. A serious statement: omega-3 is a plausible building block for long-term brain health, but not a proven method to halt cognitive decline in the short term once at an advanced age.

→ Source: Wei, B. Z., Li, L., Dong, C. W., Tan, C. C., Xu, W. et al., The Relationship of Omega-3 Fatty Acids with Dementia and Cognitive Decline, American Journal of Clinical Nutrition 117(6):1096-1109 (2023); Kang, J. H. et al., Marine n-3 Fatty Acids and Cognitive Change Among Older Adults in the VITAL Randomized Trial, Alzheimer's & Dementia: Translational Research & Clinical Interventions 8:e12288 (2022)

Expert Perspectives & Protocol Breakdown

Wei, Li, Dong, Tan, and Xu follow a broad, observational approach with their 2023 meta-analysis: 48 longitudinal studies with a total of over 100,000 participants are combined to uncover long-term patterns between dietary habits or blood markers and later dementia risk. This method is statistically robust because it relies on a huge sample, but it cannot definitively separate cause and effect: people with an already healthy lifestyle may also eat more fish.

→ Source: Wei, B. Z., Li, L., Dong, C. W., Tan, C. C., Xu, W. et al., The Relationship of Omega-3 Fatty Acids with Dementia and Cognitive Decline, American Journal of Clinical Nutrition 117(6):1096-1109 (2023)

Kang and her team took the opposite path with the VITAL study: a single, randomized, placebo-controlled intervention study with a fixed daily dose (1 g of marine n-3 fatty acids) over a clearly defined period of 2 to 3 years in already older participants. This study design can separate cause and effect more cleanly, but it only covers a limited intervention period late in life. For consumers, the juxtaposition means: observational data support a long-term relationship between diet and brain health that acts over decades, while the randomized VITAL study shows that late, short-term supplementation in old age alone no longer makes a demonstrable difference.

→ Source: Kang, J. H. et al., Marine n-3 Fatty Acids and Cognitive Change Among Older Adults in the VITAL Randomized Trial, Alzheimer's & Dementia: Translational Research & Clinical Interventions 8:e12288 (2022)

Pregnancy: DHA for the child's development

A separate EFSA classification applies to pregnant and breastfeeding women: maternal intake of DHA during pregnancy contributes to the normal development of the brain and eyes in the fetus and the breastfed infant. The DGE recommends that pregnant and breastfeeding women take at least 200 mg of additional DHA per day, in addition to general omega-3 intake. Anyone wishing to supplement during pregnancy should look for a product with a clearly declared DHA content and coordinate intake with their gynecologist, especially because of the interactions described below.

→ Source: German Nutrition Society (DGE), Reference values for nutrient intake, Omega-3 fatty acids

Inflammation and joints

EPA is a precursor to inflammation-resolving messengers, which is why omega-3 is often mentioned in connection with joint discomfort and inflammatory processes. The evidence for this is positive but more moderate than in the cardiovascular area: several review articles on rheumatoid arthritis show slight to moderate improvements in joint pain and morning stiffness with omega-3 supplementation, usually as a supplement to drug therapy, not as a replacement for it. A separate EFSA claim specifically approved for joints does not exist – this effect is plausibly explained by the general inflammation-regulating effect, but should not be confused with an officially confirmed claim. In practice, this means: omega-3 can be a sensible building block alongside exercise, nutrition, and medically prescribed therapy for inflammatory joint complaints, but it is not a sole remedy for osteoarthritis or inflammatory rheumatic diseases.

How much omega-3 per day makes sense?

For healthy adults with no specific medical indication, the DGE recommends 250–300 mg of EPA+DHA per day, or alternatively two portions of fatty sea fish per week. This amount fully covers the EFSA health claims regarding the heart, brain, and vision. Higher doses – such as the 1–2 g of EPA used in depression studies or the medically supervised doses of several grams for high-risk cardiovascular patients – should be used purposefully and ideally in consultation with a physician, rather than as a general “more is better” approach. A detailed overview of practical dosage according to life situation can be found in the linked Omega-3 Dosage Guide.

Omega-3 Index: How to truly measure your own status?

Unlike vitamin D or iron, a blood test for Omega-3 status is not widely known in this country, even though it exists: The Omega-3 Index measures the proportion of EPA and DHA in the total fatty acids of red blood cell membranes. In research, it is considered a more meaningful long-term marker than a one-time snapshot in blood plasma because it reflects the intake over the last few months rather than just the last meal. In scientific literature, values of 8% or higher are generally discussed as the desired target range, while many people in Germany and the USA in studies fall well below this. An Omega-3 Index test can be performed via specialized laboratories using a finger-prick blood test and can be useful for verifying your actual dosage rather than estimating it – especially for those who already supplement with high doses or have specific goals (e.g., cardiovascular prevention). Such a test does not replace medical diagnostics, but can serve as an objective starting point before targeted supplementation.

How to recognize good fish oil? The TOTOX value

One aspect that more often determines the actual quality of Omega-3 supplements than the pure EPA/DHA content is oxidation. Fish oil oxidizes over time, which can lead to a rancid taste, "fishy burps," and reduced efficacy of the contained fatty acids. The so-called TOTOX value (total oxidation) summarizes this condition in a single index: Peroxide value × 2 + Anisidine value. The industry initiative GOED (Global Organization for EPA and DHA Omega-3s) sets a limit of 26 as the upper threshold; values below 10 are considered very good, and premium products are often significantly lower. Many cheap fish oils exceed this limit without consumers being able to tell from the product itself – a laboratory analysis certificate is the only reliable proof here, not smell or taste alone, even if a strong rancid odor is a warning signal.

→ Source: GOED (Global Organization for EPA and DHA Omega-3s), TOTOX quality standard

Fish oil or algae oil – which is better?

Classic fish oil generally provides EPA and DHA in the ratio naturally occurring in the fat of oily cold-water fish. Algae oil, derived from microalgae, is the only relevant direct EPA/DHA source for a vegan diet, as fish themselves ultimately obtain their Omega-3 fatty acids from algae in the food chain. In terms of bioavailability, both sources are considered largely comparable according to current studies, though algae oil is often DHA-dominant, while many fish oil products offer a more balanced EPA:DHA ratio or a higher EPA share. Those who follow a plant-based/vegan diet or wish to avoid fish for reasons of taste or sustainability are well-advised with algae oil, but should pay attention to the actual EPA and DHA content per serving, as this varies greatly between products. Another often overlooked advantage of algae oil: Since microalgae are cultivated rather than caught, there is no risk of the accumulation of heavy metals such as mercury, which can play a role in certain predatory fish species – although for verified, lab-tested fish oil products, this risk is also very low due to appropriate controls.

Side effects, safety, and important interactions

In standard supplement doses, Omega-3 is considered well-tolerated. The most common harmless side effect is so-called "fishy burps," which can usually be reduced by better oil quality (lower TOTOX value) or by taking it with a meal.

For whom is targeted Omega-3 intake particularly useful?

Conscious Omega-3 intake is particularly relevant for people who rarely or never eat fatty sea fish, for vegans and vegetarians (via algae oil), for pregnant and breastfeeding women (DHA focus), and for anyone specifically concerned with cardiovascular health, blood lipid levels, or their general nutrient intake. In the case of existing heart rhythm disorders, blood clotting disorders, or the use of anticoagulant medications, intake should be medically supervised, as described. Information on how to classify heart palpitations during menopause and which warning signs should be taken seriously can be found in the article Heart palpitations and racing heart during menopause.

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Frequently asked questions about Omega-3

Further reading

Omega-3 dosage: How much EPA and DHA per day is really sensible
Vitamin K2 dosage: How many µg of MK-7 per day is really sensible
Collagen dosage: How many grams per day are really effective
Magnesium effects: What studies really show regarding muscles, sleep, and stress

References & Scientific Citations

• EFSA NDA Panel (2011). Scientific Opinion on Health Claims Related to DHA, EPA and Brain, Eye, Heart, Triglycerides and Blood Pressure, EFSA Journal 9(4):2078
• Regulation (EC) No 1924/2006 in conjunction with the EU Register of authorized nutrition and health claims.
• German Nutrition Society (DGE). Reference values for nutrient intake, Omega-3 fatty acids
• Bhatt, D. L. et al. (REDUCE-IT Investigators) (2019). Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia, New England Journal of Medicine 380(1):11-22
• Liao, Y. et al. (2019). Efficacy of Omega-3 PUFAs in Depression: A Meta-Analysis, Translational Psychiatry 9:190
• Sublette, M. E., Ellis, S. P., Geant, A. L. & Mann, J. J. (2011). Meta-Analysis of the Effects of Eicosapentaenoic Acid (EPA) in Clinical Trials in Depression, Journal of Clinical Psychiatry
• Wei, B. Z., Li, L., Dong, C. W., Tan, C. C., Xu, W. et al. (2023). The Relationship of Omega-3 Fatty Acids with Dementia and Cognitive Decline, American Journal of Clinical Nutrition 117(6):1096-1109
• Kang, J. H. et al. (2022). Marine n-3 Fatty Acids and Cognitive Change Among Older Adults in the VITAL Randomized Trial, Alzheimer's & Dementia: Translational Research & Clinical Interventions 8:e12288
• GOED (Global Organization for EPA and DHA Omega-3s). TOTOX quality standard

This article is for general information and does not replace medical advice.