Omega-3 — The Anti-Inflammatory Fat Modern Diets Have Crowded Out

The body needs omega-3 to build brains, resolve inflammation, and protect the heart. But the modern food supply has so flooded us with omega-6 from seed oils that the omega-3 you do eat has to fight for the same enzymes — and often loses.

15–20:1 Typical Western omega-6:omega-3 ratio; ancestral diets ran closer to 1:1–4:1

5–10% The rate at which plant ALA converts to EPA in healthy adults — to DHA, often less

30–40% The proportion of fatty acids in brain grey matter that is DHA — the brain is literally built from it

What Omega-3 Actually Does

Omega-3 is an umbrella term for a family of polyunsaturated fatty acids. There are three that matter for human health. ALA (alpha-linolenic acid) is found in plants — flaxseeds, chia seeds, walnuts. The body cannot make it, so it is classified as essential. EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are the biologically active forms the body actually uses. ALA must be converted to these before it can do most of its important work — and that conversion, as we will come to, is the central problem for most Western diets.

Inflammation — the balance at the heart of everything

Inflammation is not a disease. It is a biological process the body uses to fight infection and repair injury — fast, targeted, and designed to switch off once the threat has passed. The problem arises when inflammation becomes chronic: low-grade, systemwide, and never fully resolved.

EPA and DHA are the raw material for a class of molecules called resolvins, protectins, and maresins — compounds the body makes to actively resolve inflammation once it has done its job. They signal the immune system to stand down. They clear cellular debris. They return tissue to its resting state. Without adequate EPA and DHA, the resolution of inflammation is impaired — not just the initiation of it. This is why omega-3 is genuinely anti-inflammatory rather than simply anti-inflammatory-signalling.

Omega-6 fatty acids, by contrast — particularly arachidonic acid — tend to produce pro-inflammatory signalling molecules. Both families are necessary. The ratio between them determines the inflammatory tone of the body. An ancestral diet with a 2:1 or 4:1 omega-6:omega-3 ratio allowed those systems to stay in balance. A modern ratio of 15:1 or higher tips the balance persistently towards the inflammatory side.

Brain structure and function

DHA is the most abundant omega-3 fatty acid in the brain, comprising around 30–40% of the fatty acids in grey matter. It is not just a signalling molecule — it is literally a structural component of neuronal cell membranes, embedded in the phospholipid bilayer that surrounds every neuron. Membrane fluidity, the speed at which signals pass between cells, the formation and maintenance of synapses: all depend on adequate DHA being present in the membrane.

During fetal development and the first two years of life, the brain's demand for DHA is extraordinary. The fetal brain more than doubles in size in the last trimester alone, and it draws DHA from maternal stores. Inadequate maternal DHA intake during pregnancy is associated with lower cognitive scores and visual acuity in offspring. This is why DHA supplementation during pregnancy is widely recommended beyond what food alone typically provides.

In adults, low DHA status is consistently associated with faster cognitive decline and higher dementia risk in population studies, though whether supplementation reverses this is less clear — the brain's structure is built over decades, and what you ate at 30 influences the architecture you have at 60.

Cardiovascular health

EPA and DHA work on several cardiovascular risk factors simultaneously. They reduce blood triglyceride levels — consistently, across dozens of trials — by reducing hepatic triglyceride synthesis. They modestly reduce resting blood pressure. They reduce platelet aggregation, making blood less likely to clot inappropriately. And they have anti-arrhythmic properties, stabilising the electrical signalling of the heart.

Population evidence linking higher omega-3 intake (and higher blood omega-3 levels) to lower cardiovascular mortality has been consistent for decades. The evidence from supplementation trials in people who already have heart disease is more mixed — the benefit is smaller and inconsistent when measured on top of modern drug therapy. But the baseline population picture is clear: societies with high long-chain omega-3 intake from marine foods have markedly lower rates of heart disease than those that do not.

Eye health and fetal development

DHA is highly concentrated in the retina, particularly in the photoreceptor cells (rods and cones) that convert light into electrical signals. The photoreceptor outer segment membranes can be over 50% DHA. This concentration is not coincidental — the extreme membrane fluidity that DHA confers is precisely what allows photoreceptors to change shape in milliseconds in response to light.

Long-term low DHA intake is associated with an increased risk of age-related macular degeneration (AMD), the leading cause of vision loss in older adults in the UK. The association between higher dietary omega-3 and reduced AMD risk appears in multiple large prospective studies, including the AREDS2 trial.

Mental health and mood

Of the three omega-3 fatty acids, EPA has the strongest evidence for mood effects — stronger than DHA in most head-to-head comparisons. The mechanism is not fully understood but likely involves EPA's role in reducing neuroinflammation, modulating neurotransmitter signalling, and supporting the production of serotonin. EPA-dominant fish oil preparations have been used in randomised trials for depression, with results sufficiently consistent to be included in clinical guidelines in some countries.

Low omega-3 status is one of the most reliably observed nutritional associations with depression and anxiety in population studies. Whether this is causal, or whether depression reduces appetite for omega-3-rich foods, or whether underlying inflammatory states cause both, is not fully resolved. But the association is robust, and the intervention plausible enough to be worth taking seriously.

The conversion problem — why flaxseed alone may not be enough.

Plant foods provide ALA. The body needs EPA and DHA. The enzyme delta-6-desaturase converts ALA to EPA, and EPA can then be further converted — with difficulty — to DHA. The conversion rate of ALA to EPA in healthy adults is roughly 5–10%. To DHA, it drops to 0.5–5%.

That low conversion rate is further reduced by the same omega-6 that dominates the modern diet. Delta-6-desaturase is the same enzyme that processes omega-6 (linoleic acid) into its downstream forms. When omega-6 is present in large excess — as it is when seed oils dominate the diet — it outcompetes ALA for the enzyme. The result: not only is the ratio wrong, but the conversion machinery is occupied by the wrong substrate.

Eating flaxseed matters. But if the diet is also high in seed oils, most of that ALA conversion is being blocked at the enzyme level. Reducing omega-6 and eating ALA-rich foods are two complementary strategies, not alternatives.

What's Robbing Your Omega-3

Seed oils in almost everything: Sunflower oil, vegetable oil, corn oil, and soybean oil are extremely high in omega-6 linoleic acid. They are the dominant fat in the majority of processed food, takeaways, restaurant frying, and commercial cooking. Each tablespoon of sunflower oil adds roughly 9g of omega-6 — enough to overwhelm the conversion enzymes that ALA depends on.
No direct EPA/DHA source: Without oily fish or algae-based supplementation, long-chain omega-3 simply may not be arriving in the body in the amounts the brain, heart, and immune system need. ALA conversion is too variable and too inefficient to be relied on as a sole source.
Trans fats: Still present in some partially hydrogenated oils and ultra-processed products. Trans fats directly inhibit delta-6-desaturase — the same enzyme responsible for ALA conversion — compounding the omega-6 problem.
Alcohol: Heavy and regular alcohol consumption reduces the efficiency of ALA to EPA/DHA conversion and increases oxidative breakdown of omega-3 fatty acids already incorporated into cell membranes.
Zinc or vitamin B6 deficiency: Both are cofactors in the delta-6-desaturase enzyme system. Suboptimal zinc or B6 — common on restrictive diets — further impairs the already-limited ALA conversion pathway.

The oil in your cupboard may matter more than the flaxseed on your porridge.

Switching from sunflower or vegetable oil to olive oil (which is predominantly monounsaturated, not omega-6) dramatically improves the omega-6:omega-3 ratio — without adding any omega-3 at all. Reducing the omega-6 load is half the solution. It makes the ALA you do eat more likely to convert, and gives the EPA and DHA you take or absorb less competition for incorporation into cell membranes.

Extra-virgin olive oil for cooking and dressings. Minimal seed oil from processed foods. This single change shifts the ratio more than any supplement can compensate for if the underlying diet remains high in omega-6.

Wholefood Omega-3 Sources

The plant omega-3 picture divides cleanly into two categories: ALA sources (the plant form that requires conversion) and direct EPA/DHA sources (from algae — where fish themselves get theirs from). Both matter. Neither is sufficient on its own for most people eating a plant-dominant diet.

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Ground Flaxseed (Linseed)

~6,400mg ALA per 30g (2 tbsp)

The richest plant ALA source. Must be ground — whole seeds pass through largely undigested. Buy pre-ground or grind fresh. Store in the fridge once ground. Add to porridge, yoghurt, or smoothies.

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Chia Seeds

~5,100mg ALA per 30g (2 tbsp)

Highly practical — no prep needed, swell in liquid to form a gel. The whole seed is bioavailable, unlike flaxseed. Exceptional ALA content. Mix into water, oat milk, or scatter over food.

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Walnuts

~2,500mg ALA per 30g (small handful)

The only tree nut with a meaningful omega-3 contribution. Also provides vitamin E, magnesium, and polyphenols. Eat raw or lightly toasted — high heat damages polyunsaturated fats. Not a substitute for flaxseed, but a useful daily habit.

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Hemp Seeds (Shelled)

~2,600mg ALA per 30g (3 tbsp)

A more balanced omega-6:omega-3 ratio than most nuts and seeds, which makes hemp seeds a particularly good choice — the omega-6 in hemp is lower relative to ALA than in many alternatives. Complete protein too.

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Algae Oil (DHA + EPA)

~400–1,000mg EPA+DHA per capsule/serving

The plant-based answer to the conversion problem. Algae produce DHA and EPA directly — fish accumulate it by eating algae. Algae oil goes straight to the source. Clinically validated, sustainable, and the recommended approach for plant eaters who do not consume oily fish.

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Edamame (Young Soy)

~280mg ALA per 100g cooked

Lower ALA than seeds, but a meaningful contribution alongside a complete protein and good source of choline. The omega-6:omega-3 ratio in soy is less favourable than in hemp or flaxseed, but as a whole food (rather than oil), soy is not a major omega-6 concern.

Algae Oil — The Plant Eater's Direct EPA/DHA Source

Who needs it: Anyone eating a primarily plant-based or vegetarian diet, or anyone whose oily fish intake is irregular. ALA conversion rates are simply too variable and too easily blocked by omega-6 to rely on as a sole source of EPA and DHA. This includes people who are eating plentiful flaxseed and walnuts — if their diet is also high in seed oils, conversion may still be inadequate.
What it is: Algae oil is extracted from microalgae — the same organisms that form the base of the marine food chain and are the original source of DHA in fish. It provides EPA and DHA directly, bypassing the conversion step entirely. It is routinely used in clinical trials as the plant-based equivalent of fish oil and has equivalent bioavailability.
Dose: A daily intake of 250–500mg EPA+DHA combined is appropriate for general health maintenance. During pregnancy and breastfeeding, an additional 200mg DHA/day is widely recommended on top of this. Higher doses (1–2g/day EPA+DHA) are sometimes used therapeutically for triglycerides or inflammatory conditions — discuss with a GP or dietitian.
Timing: Take with a meal containing fat — omega-3 absorption is significantly enhanced in the presence of dietary fat. The main meal of the day is ideal.
Flaxseed oil vs algae oil: Flaxseed oil provides concentrated ALA — useful for boosting the precursor pool — but still requires conversion to EPA and DHA. It is not a substitute for algae oil if EPA and DHA are the goal. Flaxseed oil and algae oil serve different purposes and complement each other.
Storage: Omega-3 oils oxidise easily. Keep algae oil capsules (or liquid) in the fridge away from light. Rancid omega-3 produces aldehydes and other oxidation products — if an oil tastes fishy (algae oil should not) or bitter, discard it.

Essential plant form

ALA (alpha-linolenic acid)

Active long-chain forms

EPA + DHA

UK adult target

250mg EPA+DHA/day (EFSA)

Highest plant ALA source

Ground flaxseed (~6,400mg/30g)

Direct plant EPA+DHA source

Algae oil supplements

ALA→EPA conversion rate

5–10% in healthy adults

Main omega-6 culprit

Sunflower / vegetable / corn oil

Preferred cooking oil swap

Extra-virgin olive oil

"Fish don't make omega-3. They eat algae. The entire supply chain for EPA and DHA leads back to the same microorganisms — which means the plant-based solution already exists, and it doesn't require a single fish."

— Editorial, Nutriofia

Smart Pairings

Ground flaxseed + oat porridge with berries — the fat in the oats helps absorption; berries provide antioxidants that protect polyunsaturated fats from oxidation
Chia seeds + plant milk overnight oats — overnight soaking increases bioavailability; the fat in nut milks aids absorption
Walnuts + dark leafy greens — vitamin K in the greens and ALA from the walnuts both support cardiovascular health independently
Algae oil capsule + main meal — always with dietary fat for maximum absorption; taking it on an empty stomach significantly reduces uptake
Switch sunflower oil → olive oil — every meal cooked this way incrementally improves the omega-6:omega-3 ratio without adding a single milligram of omega-3
30 plant foods per week + algae oil — the plant variety target from the Fibre page also naturally diversifies ALA sources and reduces the ultra-processed food that dominates the omega-6 load

References

Simopoulos AP. "The importance of the ratio of omega-6/omega-3 essential fatty acids." Biomed Pharmacother. 2002;56(8):365–379.
Brenna JT. "Efficiency of conversion of alpha-linolenic acid to long chain n-3 fatty acids in man." Curr Opin Clin Nutr Metab Care. 2002;5(2):127–132.
Blasbalg TL et al. "Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century." Am J Clin Nutr. 2011;93(5):950–962.
Calder PC. "Omega-3 fatty acids and inflammatory processes: from molecules to man." Biochem Soc Trans. 2017;45(5):1105–1115.
Innis SM. "Dietary omega 3 fatty acids and the developing brain." Brain Res. 2008;1237:35–43.
Appleton KM et al. "Omega-3 fatty acids for depression in adults." Cochrane Database Syst Rev. 2015;11:CD004692.
Eaton SB, Konner M. "Paleolithic nutrition: a consideration of its nature and current implications." N Engl J Med. 1985;312(5):283–289.
EFSA Panel on Dietetic Products. "Scientific Opinion on Dietary Reference Values for fats, including saturated fatty acids, polyunsaturated fatty acids, monounsaturated fatty acids, trans fatty acids, and cholesterol." EFSA Journal. 2010;8(3):1461.