What Is DHA (Docosahexaenoic Acid)?

DHA stands for docosahexaenoic acid, a long-chain omega-3 fatty acid with 22 carbon atoms and six double bonds. It is the most abundant omega-3 in the human brain and retina, which tells you something immediate about where your body concentrates its supply.

Pick up any omega-3 supplement in a health shop and you will find DHA on the back label. What you will not find is an honest explanation of how little your body can make on its own.

The conversion from ALA (alpha-linolenic acid, found in flaxseed and walnuts) to DHA is poor. Published estimates put it below 5%, and the bottleneck worsens with age, high omega-6 intake, and certain genetic variants. If you do not eat oily fish, relying on that conversion pathway is not a reliable strategy.

That makes the question of where to get DHA directly, and how to evaluate what you are buying, genuinely important rather than merely academic. We have spent enough time comparing products in this category to know that the label alone rarely tells you what matters.

DHA in Plain Terms

What DHA Is Chemically

DHA is a 22-carbon polyunsaturated fatty acid with six cis double bonds, the longest and most unsaturated of the omega-3 fatty acids commonly discussed in nutrition. Its structure makes it unusually fluid at cell membrane level, which is why the body preferentially incorporates it into tissues requiring rapid signal transmission: the brain, the retina, and to a lesser extent cardiac muscle.

When we review the science on omega-3 fatty acids, this structural fluidity is what makes DHA distinct from EPA and ALA. It is not simply another omega-3. It is the one your nervous system actively hoards.

You will sometimes see DHA written as C22:6 n-3 on technical labels. The "n-3" designates where the first double bond sits relative to the methyl end of the molecule. This is the same naming convention that classifies all omega-3 fatty acids.

Why Your Body Cannot Make Enough DHA

The conversion pathway from ALA to DHA runs through several enzymatic steps: ALA to stearidonic acid, then to eicosatetraenoic acid, then to EPA, and finally to DHA via an additional elongation and desaturation step. Each step loses efficiency. The final conversion to DHA is the most restricted, which is why published estimates put the overall ALA-to-DHA yield below 5% in most adults (Burdge and Calder, 2005).

For context, you would need to consume a substantial quantity of flaxseed oil daily to match the DHA in a single algae oil capsule. We find this is the point that most surprises people when we explain it: if your diet contains no oily fish and no direct DHA supplement, your circulating DHA levels are likely lower than you assume.

Where DHA Originates in the Food Chain

Microalgae as the Original DHA Producers

Fish do not synthesise DHA. They accumulate it by eating smaller organisms that eat microalgae. The DHA in a salmon fillet originated in the marine food chain's base. When you take a fish oil capsule, you are consuming DHA that passed through several trophic levels before reaching you.

We think this is worth understanding because it changes how you evaluate your options. Going directly to the source is not a marketing gimmick, it is a shorter supply chain.

The species most relevant to DHA production is Schizochytrium, a marine protist (technically a thraustochytrid, not a true alga) that produces DHA in high concentrations. Most commercial algae-derived DHA supplements use Schizochytrium grown in fermentation tanks. This is a controlled, scalable process that bypasses the fish entirely.

DHA Sources in Food and Supplements

Oily fish remain the most concentrated whole-food source. A 140g portion of grilled salmon provides roughly 1,000-1,500 mg of DHA. Mackerel, sardines, and herring are comparable. Two portions of oily fish per week, the standard NHS recommendation, typically delivers enough DHA to meet EFSA intake conditions without supplementation.

If you do not eat fish, your options narrow to algae-derived DHA supplements (from Schizochytrium) or fortified foods. Some plant milks and eggs are DHA-fortified, but the amounts per serving are usually modest, often under 50 mg. We have seen fortification levels vary so widely between brands that checking the label is not optional.

Roles of DHA in the Brain, Eyes, and Heart

EFSA-Authorised Health Claims for DHA

The regulated claims here are tightly worded, and we think that precision is a feature, not a limitation. DHA contributes to the maintenance of normal brain function. DHA contributes to the maintenance of normal vision. Both claims are authorised by EFSA under Commission Regulation (EU) No 432/2012 at a daily intake of 250 mg DHA.

EPA and DHA together contribute to the normal function of the heart at a combined intake of 250 mg per day. This is a joint claim; it does not apply to DHA alone or EPA alone in isolation.

DHA in Pregnancy and Infant Development

Maternal DHA intake contributes to the normal development of the eye and brain of the foetus and breastfed infant. The EFSA intake condition is 200 mg DHA daily on top of the recommended 250 mg combined EPA+DHA. That is a combined target of 450 mg per day.

This number catches many people off guard. If you pick up a standard DHA supplement at Boots or your local pharmacy and turn it over, a single capsule often provides 200-250 mg of DHA. During pregnancy, you may need two capsules daily to reach the combined threshold.

We have walked through this arithmetic with enough customers to know it is genuinely confusing at the till. The product and whether you eat any oily fish both affect the calculation.

Worth noting: the authorised claims are bounded. DHA supports maintenance of normal brain function and normal vision — not "improves memory" or "prevents dementia." The gap between maintenance and enhancement is wider than most supplement marketing suggests.

Why DHA and EPA Are Not Interchangeable

Structural DHA vs Signalling EPA

DHA and EPA are both long-chain omega-3 fatty acids, but they serve different biological roles. DHA is a structural component, concentrated in neural membranes and the retina. EPA is more active in the body's eicosanoid signalling pathways, involved in inflammatory regulation and cardiovascular function.

Most omega-3 research uses combined EPA+DHA supplementation, which makes it difficult to attribute specific outcomes to one fatty acid alone. Products marketed for "brain health" typically emphasise DHA, but the evidence they lean on usually tested DHA and EPA together.

We think that distinction matters when you are deciding what to buy and why. Any product suggesting it delivers targeted brain benefits from DHA alone is overstating what the research actually isolated.

How Algae Species Determine the EPA-DHA Split

Different microalgae species produce different fatty acid profiles. Schizochytrium produces primarily DHA with relatively little EPA. Nannochloropsis gaditana, the species used in marine phytoplankton supplements, produces primarily EPA with very little DHA. They are complementary, not interchangeable.

If your goal is both EPA and DHA from non-fish sources, you need both types of product. A DHA-rich algae oil covers one side. An EPA-rich phytoplankton supplement covers the other. This is a biological constraint, not a marketing convenience.

DHA Intake Targets and Who Needs More

General Adult DHA Requirements

For the general adult population, 250 mg of DHA per day is the threshold for the EFSA-authorised brain function and vision claims. If you eat two portions of oily fish per week (a tin of sardines on toast for lunch, grilled mackerel at the weekend) you are likely meeting this without supplementation.

If you eat no fish at all, we can say with reasonable confidence that you are not meeting that threshold through diet alone.

There is no official upper limit set by EFSA for DHA specifically, though the panel has assessed combined EPA+DHA intakes up to 5 g per day as not raising safety concerns for the general adult population. Most supplements provide 200-500 mg of DHA per dose, well within that range.

DHA Needs During Pregnancy and Breastfeeding

The 200 mg additional DHA during pregnancy is on top of the baseline 250 mg EPA+DHA recommendation. If you are pregnant and not eating oily fish, you need to look carefully at your supplement label. A product providing 250 mg DHA per capsule gets you most of the way there, but you still need EPA coverage. Two separate supplements or a combined product may be necessary.

This is one of those areas where the arithmetic matters more than the reassuring front-of-pack claim. We have looked at products marketed as "pregnancy omega-3" that provide 200 mg DHA and 50 mg EPA per capsule. That technically meets the DHA add-on condition but leaves you short on total EPA+DHA unless you have dietary sources as well.

Evaluating DHA on a Supplement Label

Total Omega-3 vs Actual DHA Content

The front of most omega-3 packaging shows a total omega-3 figure. That number frequently bundles DHA, EPA, and sometimes ALA or other fatty acids into one headline claim. Open any "1000 mg omega-3" softgel box from the health shop shelf, flip to the nutritional panel, and you may find only 200 mg of actual DHA inside. The gap between the front-of-pack claim and the per-capsule reality is where confusion lives.

If your goal is a specific DHA intake, you need the per-capsule DHA figure from the nutritional information panel. We list individual fatty acid amounts on our own labels for this reason. The total omega-3 number on the front is marketing shorthand, not a useful dosing guide.

Triglyceride and Ethyl Ester DHA Forms

DHA in supplements exists in two main molecular forms. Triglyceride-form DHA is closer to how the fatty acid exists naturally in whole fish and algae. Ethyl ester DHA is a semi-synthetic form created during the concentration process used in many fish oil products.

Published research suggests triglyceride-form omega-3s show 50 to 70% higher absorption compared to ethyl esters (Dyerberg et al., 2010). If two products contain the same amount of DHA on the label but one is triglyceride-form and the other ethyl ester, the amount reaching your cells will differ. We consider this the most underappreciated variable in omega-3 supplementation.

This is worth checking when you compare products at similar price points. Cut open a triglyceride-form algae oil capsule and you get a clean, faintly marine-smelling oil with a golden tint. Do the same with an ethyl ester fish oil and the smell is sharper, more pungent.

We reviewed multiple formulation options before selecting the oil for our own DHA supplement. The sensory difference alone told us something about oxidation stability.

What Sourcing Algae-Derived DHA Taught Us

We have sourced, tested, and reformulated algae-based omega-3 products over several years. Some of what we learned was expected. Some of it changed how we read every competitor label on the shelf. These are the insights that stuck.

DHA and EPA come from different algae species. Schizochytrium produces DHA in high concentrations but almost no EPA. Nannochloropsis produces EPA with negligible DHA. If you want both fatty acids from non-fish sources, you need two separate products. No single algae species delivers a balanced EPA+DHA profile.

Algae-derived DHA oxidises differently from fish oil DHA. We noticed this when cutting open capsules from different suppliers. Fish oil ethyl esters develop a sharp, rancid smell faster than triglyceride-form algae oil stored under the same conditions. The shorter supply chain and fewer processing steps appear to give algae oil a stability advantage.

A label saying "omega-3" without specifying DHA and EPA milligrams tells you nothing useful. We have seen products advertise 1,000 mg of omega-3 per capsule where the actual DHA content was under 150 mg. The rest was ALA, other fatty acids, or filler oil. If the back panel does not break out DHA and EPA individually, treat the front-of-pack claim as decoration.

Triglyceride form absorbs substantially better than ethyl ester form. Published data suggests 50 to 70% higher bioavailability for triglyceride-form omega-3s. We chose triglyceride form for our own DHA product after reviewing absorption data and cutting open capsules from both categories. The difference is measurable, not theoretical.

Most people need a combined EPA and DHA strategy, not one or the other. The EFSA heart-function claim requires both EPA and DHA together at 250 mg combined daily. If you take a DHA-only algae oil, you cover brain and vision claims but leave the EPA side uncovered. We built our product range around this reality: EPA from phytoplankton, DHA from Schizochytrium algae oil.

Common Questions About DHA Supplements

Can your body make DHA from plant-based omega-3s?

Technically yes, but the yield is poor. Your body converts ALA through a multi-step enzymatic process, and the final step to DHA is the least efficient. Published conversion estimates sit below 5%. Women of reproductive age convert slightly more efficiently than men, likely due to oestrogen's effect on the desaturase enzymes, but the rate is still too low to rely on as a primary DHA strategy.

How much DHA should you take per day?

EFSA-authorised health claims specify 250 mg DHA daily for normal brain function and normal vision. During pregnancy and breastfeeding, an additional 200 mg DHA on top of 250 mg combined EPA+DHA supports foetal brain and eye development. That combined target of 450 mg is higher than many supplement labels deliver per single dose.

We recommend sitting down with your product's nutritional panel and a calculator. The arithmetic is not difficult, but no one does it at the till.

Is algae-derived DHA identical to fish oil DHA?

The DHA molecule is the same regardless of whether it comes from fish oil or algae oil. Fish accumulate DHA from microalgae through the food chain; algae-derived supplements go directly to the source. The practical differences are in the accompanying fatty acid profile (algae oils tend to be DHA-dominant with less EPA) and the molecular form (triglyceride vs ethyl ester), which affects absorption.

Can you take too much DHA?

EFSA has assessed supplemental intakes of EPA and DHA combined up to 5 g per day as not raising safety concerns for the general adult population. Most supplements provide 200-500 mg of DHA per dose, so you would need a large number of capsules to approach that ceiling.

If you are taking blood-thinning medication, speak to your GP before starting high-dose omega-3 supplementation. EPA and DHA may have mild anticoagulant effects at elevated intakes, and your GP can advise on what dose is appropriate alongside your existing prescription.

Does DHA go off or oxidise in supplements?

Omega-3 fatty acids are susceptible to oxidation, which degrades potency and produces an unpleasant fishy smell. Here is a practical test: open your bottle and sniff. A fresh DHA supplement should smell faintly marine at most. If it hits you with a sharp, rancid fish odour, oxidation has already begun and potency is compromised.

Algae-derived DHA supplements tend to be more stable than fish oils because the extraction process introduces fewer oxidation opportunities. Store your capsules in a cool, dark cupboard, not on the kitchen windowsill, and check the expiry date.

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Consult your healthcare provider before starting any supplement.

Methodology and Disclosure

Phytality manufactures an algae-derived DHA supplement (Clean Omega DHA) using Schizochytrium-sourced oil in triglyceride form. We have a direct commercial interest in this product category. This article is written to provide accurate, evidence-based information about DHA as a nutrient, not as product marketing.

EFSA-authorised health claims are cited under Commission Regulation (EU) No 432/2012 with intake conditions stated. ALA-to-DHA conversion estimates draw on Burdge and Calder (2005). Bioavailability comparisons between triglyceride and ethyl ester forms reference Dyerberg et al. (2010). The EFSA safety assessment for combined EPA+DHA intakes references the 2012 tolerable upper intake opinion.

Comparisons between algae species (Schizochytrium vs Nannochloropsis) reflect established compositional differences documented in the cited literature. Where we describe our own product formulation choices, this reflects our actual sourcing and manufacturing process.

Last reviewed: March 2026. Next review due: March 2027.