Omega-3: what are the health benefits?

Few nutrients have garnered as much interest. Heart, brain, eyes, skin: the benefits of omega-3s are cited everywhere, sometimes beyond what science currently allows us to claim. Yet, behind this generic term lie very specific molecules with distinct functions.

Some of these effects are firmly established and recognized by European health authorities. Others remain promising but have yet to be confirmed.

To separate fact from supposition, three questions come up constantly. What do these fatty acids actually do? Is it worthwhile to consume them every day? And are there limits to their supplementation? This report takes stock of omega-3s and their benefits, supported by studies.

Omega-3s are polyunsaturated fatty acids. Their name comes from their chemical structure: the first double bond of their carbon chain is located on the third carbon, starting from the so-called "omega" end.

This molecular detail has a very concrete consequence. It conditions the flexibility of the membranes into which these fatty acids are inserted, and therefore the functioning of the cells that contain them.

Alpha-linolenic acid (ALA) is the plant-based omega-3. It is present in flaxseeds, walnuts, rapeseed oil, or chia seeds. The body mainly uses it as a source of energy and as a precursor for long-chain forms.

Eicosapentaenoic acid (EPA) is primarily of marine origin. It serves as a starting point for the synthesis of lipid mediators, eicosanoids and resolvins. These molecules participate in the body's defense reactions and then in their resolution.

Docosahexaenoic acid (DHA) is the quintessential structural omega-3. It is particularly concentrated in the membranes of neurons and in the photoreceptors of the retina.

In other words, speaking of the benefits of omega-3s as a group makes little sense: EPA and DHA do not perform the same functions as ALA, and they are the ones that carry most of the documented effects.

Humans do not possess the enzymes, called desaturases, capable of creating a double bond in the omega-3 position. ALA is therefore an essential fatty acid in the strict sense: it must be provided through diet.

EPA and DHA are said to be "conditionally essential." The body can produce them from ALA, but with such a low yield that a direct intake remains necessary to cover requirements.

Once absorbed, these essential fatty acids integrate into the phospholipids of cell membranes. Their presence influences membrane fluidity, communication between cells, and the activity of many receptors.

Omega-6s, mainly linoleic acid, are also essential. But they use the same transformation enzymes as omega-3s. The two families are therefore in constant competition.

According to the reference work of Artemis Simopoulos, the contemporary Western diet exhibits an omega-6 / omega-3 ratio in the order of 15 to 20 to 1. This is far from the proportions observed in traditional diets. ANSES recommends a linoleic acid / ALA ratio of less than 5.

This imbalance has a direct consequence: an excess of omega-6 further limits the conversion of ALA into EPA and DHA. Rebalancing this ratio depends as much on the quality of cooking oils as on increasing omega-3 intake.

Health claims authorized in the European Union are governed by Regulation (EU) No 432/2012. Each is based on a scientific assessment by EFSA and is accompanied by a minimum intake threshold. It is this framework that allows us to distinguish established omega-3 benefits from pathways that are still exploratory.

EPA and DHA contribute to normal heart function, for a daily intake of 250 mg. This is the most emblematic effect associated with omega-3s for the heart.

At the cellular level, these fatty acids integrate into cardiomyocyte membranes. There, they influence the activity of ion channels that govern the electrical activity of the heart.

Large intervention studies, however, invite nuance. A Cochrane review published in 2020 gathered more than 80 randomized trials and more than 160,000 participants. It concluded that increasing EPA and DHA intake has weak, if any, effects on several major cardiovascular criteria.

The American VITAL trial, conducted on nearly 26,000 adults receiving 1 g of omega-3 per day for about five years, also showed no significant effect on its primary endpoint. In other words, omega-3s for the heart are part of a global lifestyle, not a matter of an isolated effect.

The brain is one of the organs richest in lipids, and DHA is by far the most abundant omega-3 in it. DHA contributes to normal brain function, for an intake of 250 mg per day.

This link between omega-3s and the brain is explained by the very structure of neurons. Synaptic membranes, rich in DHA, condition the transmission of nerve impulses and the plasticity of connections.

In aging adults, intervention results remain mixed. The MIDAS randomized trial followed 485 adults over 55 receiving 900 mg of algal DHA per day for 24 weeks. It observed an improvement in certain episodic memory parameters compared to the placebo. Other trials did not find these effects, which invites us to interpret this data with caution.

DHA is among the nutrients studied in dietary supplements for memory.

The retina is among the tissues with the highest concentration of DHA in the body. In the outer segments of photoreceptors, this fatty acid can account for nearly half of the membrane fatty acids.

DHA thus contributes to the maintenance of normal vision, for an intake of 250 mg per day. This link between omega-3s and vision is due to the membrane flexibility necessary for transforming light into a nerve signal.

The AREDS2 study followed more than 4,000 participants. It did not highlight any additional benefit from adding EPA and DHA on the evolution of age-related macular health. The structural role of DHA remains established, but the value of additional intake for people already well-nourished is less clear.

Two authorized claims concern these parameters. They are, however, based on intakes significantly higher than those mentioned so far:

• EPA and DHA contribute to the maintenance of normal triglyceride levels, from 2 g per day;
• they contribute to the maintenance of normal blood pressure, from 3 g per day.

In both cases, regulations require specifying that the supplementary intake should not exceed 5 g per day of combined EPA and DHA.

The link between omega-3s and triglycerides is explained by a modulation of the hepatic synthesis of triglyceride-rich lipoproteins. On the plant side, ALA contributes to the maintenance of normal cholesterol levels, for an intake of 2 g per day.

The skin is one of the most explored areas in nutricosmetics. This is the field in which Biocyte, a French nutricosmetics laboratory, has made its area of expertise.

Polyunsaturated fatty acids participate in the composition of keratinocyte membranes. Linoleic acid, an omega-6, is also a key precursor to the ceramides of the skin barrier. This role of lipids in the skin barrier is one of the levers for hydrating your skin from the inside.

Regarding omega-3s, several small-scale controlled trials, involving a few dozen participants, have studied EPA at high doses over several weeks. They observed a modification in the skin's response to UV exposure, with a higher threshold for the appearance of redness.

These results, synthesized in particular by Lesley Rhodes' team, nevertheless remain preliminary. There are currently no health claims linking omega-3s to the skin. They are no substitute for appropriate photoprotection or a cosmetic routine.

EPA and DHA are present in neuronal membranes and are involved in the synthesis of lipid mediators. This role has led to studies on their link with emotional balance.

Several meta-analyses suggest an interest in EPA-dominant formulas regarding certain mood indicators. However, the results remain very heterogeneous from one study to another.

Joint comfort is also the subject of research, particularly concerning morning stiffness. Here again, no claim is authorized. For a more comprehensive approach to emotional balance, our article on natural anti-stress remedies provides an overview of other avenues. Any persistent discomfort, whether emotional or joint-related, should be discussed with a healthcare professional.

This table summarizes the essentials: the benefits of omega-3s recognized by regulations are numerous, but each depends on a specific intake threshold and a specific form of fatty acid.

In the absence of truly characteristic signs, an insufficient intake of omega-3s often goes unnoticed: however, certain clues may alert you, and only a blood test can confirm it for sure.

Dry and rough skin, dull hair, brittle nails, or diffuse fatigue are sometimes associated with insufficient intake of essential fatty acids. However, these signs remain very non-specific: they can have many other origins. Dull hair also depends largely on hair care, as detailed in our guide to achieving shiny hair.

The only objective indicator is biological. The omega-3 index, proposed by William Harris and Clemens von Schacky in 2004, measures the proportion of EPA and DHA in red blood cell membranes. A value greater than or equal to 8% is considered favorable, and a value close to 4% is considered low. This blood test is performed in a laboratory, upon the advice of a healthcare professional.

French consumption studies show that EPA and DHA intakes remain below recommendations for a large part of the population. Several profiles are particularly affected:

• people who eat little or no fish;
• vegetarians and vegans, deprived of direct sources of EPA and DHA;
• pregnant or breastfeeding women, whose DHA needs increase;
• seniors and the elderly;
• people whose diet is very high in omega-6s.

Omega-3s are found in seafood as well as in certain plants, but these sources do not provide the same fatty acids: knowing them well allows you to cover your needs in ALA, EPA, and DHA.

Foods rich in omega-3s in the form of EPA and DHA are primarily small fatty fish: sardines, mackerel, herring, anchovies. Next come salmon and trout, as well as certain seafood such as oysters and mussels.

ANSES recommends eating fish twice a week, including one fatty fish, while varying the species and sources. This diversity limits exposure to environmental contaminants like mercury.

The main sources of plant-based omega-3s are flaxseed oil, which is highly concentrated in ALA, rapeseed oil, walnut oil, as well as ground flaxseeds and chia seeds.

These oils are delicate. They should be stored in the refrigerator, away from light, and are best used raw, as seasoning. Prolonged cooking alters their fatty acids.

A reference review by Graham Burdge and Philip Calder estimates that only a few percent of ALA is converted into EPA in adults. Conversion into DHA is even lower, often less than 1% in men. It is slightly higher in women, due to the influence of estrogen.

In practice, a plant-based omega-3 like flaxseed oil meets ALA requirements, but not those for EPA and DHA. For those who do not consume seafood, algal oil is the only direct plant source of DHA, and sometimes EPA.

Omega-3 requirements are expressed for each fatty acid separately, and health authorities have set specific benchmarks for adults, to be adjusted according to certain stages of life.

The updated recommended nutritional intakes published by ANSES in 2011 set, for an adult:

• an ALA intake equivalent to 1% of energy intake, or approximately 2 g per day;
• 250 mg of EPA and 250 mg of DHA per day.

Regarding the daily omega-3 dosage, the EFSA also retains an adequate intake of 250 mg of combined EPA and DHA. It considers that an intake of up to 5 g per day does not raise safety issues for adults.

During pregnancy and breastfeeding, an intake of 200 mg of DHA per day, in addition to the 250 mg of EPA and DHA recommended, contributes to the normal development of the brain and eyes of the fetus and the breastfed infant. This link between omega-3s and pregnancy is one of the best documented. In case of pregnancy or breastfeeding, it is important to seek advice from a healthcare professional before any supplementation.

For athletes, no specific intake is officially defined. Research, however, is exploring the role of EPA and DHA in recovery.

For seniors, the challenge is primarily about maintaining regular intake, which often declines with age.

The effectiveness of a supplement relies on three parameters: the lipid source, its purity, and its stability. It is this demand for high-quality raw materials that Biocyte places at the heart of its nutricosmetic formulations.

Fish oil is the most common source. It is available in the form of natural triglycerides, re-esterified triglycerides, or ethyl esters. The latter allow for high concentrations of EPA and DHA to be achieved.

Krill oil provides its omega-3s in the form of phospholipids, naturally associated with astaxanthin, an antioxidant pigment. A trial by Ulven and colleagues observed metabolic effects comparable to those of fish oil, despite a lower dose of EPA and DHA. However, the content per capsule generally remains lower.

Algal oil, derived from cultivated microalgae, is suitable for vegan diets. It is especially rich in DHA.

No source is superior in all circumstances: the choice depends on diet, the target quantity of EPA and DHA, and individual preferences. These criteria complement the general benchmarks for choosing a food supplement.

The first criterion is the actual EPA and DHA content per daily dose, not the total amount of oil displayed. A 1,000 mg oil capsule may contain less than 300 mg of EPA and DHA.

The second criterion is the freshness of the oil. Polyunsaturated fatty acids oxidize easily. The TOTOX index, which combines the peroxide value and the anisidine value, provides information on this state of oxidation. Industry standards set a ceiling of 26. The addition of vitamin E helps preserve the stability of the oil.

The third criterion is origin and purification. Molecular distillation reduces contaminants, and sustainable fishing certifications such as MSC or Friend of the Sea guarantee a responsible supply chain.

No study has demonstrated any one time of day as being more favorable than another. However, taking them during a meal containing fat improves absorption, particularly for ethyl esters.

Splitting the dose between two meals can limit fishy aftertaste. Above all, consistency is what counts: fatty acids are incorporated into cell membranes gradually, over several weeks.

Omega 3s are well tolerated at recommended intakes. Some situations, however, call for special vigilance:

• people on anticoagulants or antiplatelet drugs should seek medical advice, as high doses of omega 3s can prolong coagulation time;
• before any surgical procedure, it is recommended to disclose any supplementation;
• in case of a known sensitivity to fish or shellfish, fish and krill oils should be avoided;
• cod liver oil also provides vitamin A, for which the cumulative intake from other sources should be monitored.

At high doses, some meta-analyses of clinical trials have noted changes in heart rhythm in people under cardiovascular monitoring. It is therefore advisable to respect the indicated doses and to seek advice from a healthcare professional in case of medical follow-up.

• Commission Regulation (EU) No 432/2012 of 16 May 2012 establishing a list of permitted health claims made on foods.

• ANSES. Updating of recommended nutritional intakes for fatty acids. Collective expert report, 2011.

• EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for fats. EFSA Journal 2010;8(3):1461.

• EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the Tolerable Upper Intake Level of EPA, DHA and DPA. EFSA Journal 2012;10(7):2815.

• Abdelhamid AS et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews, 2020.

• Manson JE et al. Marine n-3 fatty acids and prevention of cardiovascular disease and cancer (VITAL). New England Journal of Medicine, 2019;380:23-32.

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

• AREDS2 Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration. JAMA, 2013;309(19):2005-2015.

• Burdge GC, Calder PC. Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults. Reproduction Nutrition Development, 2005;45(5):581-597.

• Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomedicine & Pharmacotherapy, 2002;56(8):365-379.

• Pilkington SM, Watson REB, Nicolaou A, Rhodes LE. Omega-3 polyunsaturated fatty acids: photoprotective macronutrients. Experimental Dermatology, 2011;20(7):537-543.

• 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.

• Ulven SM et al. Metabolic effects of krill oil are essentially similar to those of fish oil but at lower dose of EPA and DHA. Lipids, 2011;46(1):37-46.