DHA (Docosahexaenoic Acid)

DHA — docosahexaenoic acid — is the omega-3 fatty acid without which your brain literally cannot function properly. While EPA is primarily regarded as an anti-inflammatory agent, DHA is the actual structural building block: it forms the main component of cell membranes in your nervous system, retina, and synapses. About 60 per cent of the dry weight of the human brain consists of fat — and DHA is by far the most important omega-3 fatty acid within it. No other nutrient is so inseparably linked to the health and performance of your brain. The European Food Safety Authority (EFSA) has approved two official health claims for DHA: for normal brain function and for normal vision — both at 250 mg DHA per day. In this article you will learn everything you need to know about DHA: its chemistry, its functions in the body, the best sources, and daily requirements.

What is DHA? Chemistry and distribution in the body

Chemically, DHA is a polyunsaturated fatty acid of the omega-3 group with the molecular formula C22H32O2 and the shorthand notation C22:6n-3. This means: a carbon chain of 22 atoms with six double bonds, the first of which is at position 3 from the methyl end of the chain. These six double bonds give DHA an unusual molecular flexibility — the fatty acid can effectively "bend" and thereby confers exceptional fluidity to cell membranes.

In the body, DHA is predominantly incorporated into phospholipids — the molecules from which cell membranes are built. DHA concentration is particularly high in tissues with high energy demands and complex signal processing: in the human brain, DHA accounts for around 97 per cent of all omega-3 fatty acids. In the retina of the eye, the proportion is approximately 93 per cent of all omega-3 fatty acids present. DHA is also found in high concentrations in cardiac muscle cells, sperm cells, and breast milk.

Your body can theoretically produce DHA from the plant-based omega-3 fatty acid ALA (alpha-linolenic acid) — however, this conversion is extremely inefficient. Studies show that less than 1 per cent of ingested ALA is actually converted to DHA. In practical terms, this means: anyone who does not regularly eat oily sea fish or take a high-quality omega-3 supplement will consume almost no DHA. This is one of the reasons why most people in Western countries are DHA-deficient.

The fluidity that DHA provides to cell membranes is not trivial. It enables rapid signal transmission between nerve cells, regulates the activity of membrane-bound enzymes and receptors, and directly influences how efficiently synaptic vesicles release their contents. Without sufficient DHA, membranes become "stiffer" — with measurable effects on neural speed and plasticity.

DHA and brain health

DHA as a structural component of the brain

The human brain is the most fat-rich organ in the body — only adipose tissue itself has a higher fat content. Of all the fatty acids in the brain, DHA dominates to an extent no other fatty acid comes close to matching. It is concentrated in the phospholipids of neuronal cell membranes, particularly in the synaptic terminals where nerve cells communicate with each other.

What makes DHA so indispensable for the brain is its influence on neuroplasticity — the brain's ability to change, forge new connections, and respond to experiences. DHA promotes the production of Brain-Derived Neurotrophic Factor (BDNF), a protein that supports the growth and maintenance of nerve cells. Low DHA levels in the blood have been associated in studies with reduced brain volume in areas responsible for learning and memory.

The membrane conductance of neuronal cells — how quickly electrical signals are transmitted along nerve fibres — depends directly on the fatty acid composition of myelin sheaths. DHA is an essential component of myelin. For more on how omega-3 fatty acids affect the brain overall, see our article Omega-3 and the Brain.

DHA and cognitive performance

Several studies have examined the relationship between DHA levels in the blood and cognitive performance. A cross-sectional study with over 1,500 participants, published in the journal Neurology, showed that individuals with low omega-3 levels performed worse on tests of visual-spatial reasoning, non-verbal reasoning, and working memory compared to those with higher levels.

For age-related cognitive decline, the findings are particularly consistent. A meta-analysis published in 2020 in the Journal of Alzheimer's Disease evaluated 13 studies and found that higher DHA levels in blood plasma were associated with a slower decline in cognitive function with age. Importantly, this association does not mean that DHA supplements treat or prevent cognitive disease — such therapeutic claims are not permitted under EFSA regulations and are not sufficiently supported by evidence. What the data demonstrate is a robust correlation between adequate DHA intake and better cognitive health throughout life.

DHA is particularly relevant during periods of intensive learning. Since DHA is needed to form new synaptic connections, adequate levels during times of increased mental demand — studying, demanding projects, acquiring new skills — may play a supportive role. For more on optimal dosages for different life stages, see our Omega-3 Requirements Calculator.

DHA and mental health

Regarding mental health — particularly mood disorders — the evidence is more nuanced. Here EPA is the omega-3 fatty acid with the stronger efficacy profile in clinical trials. DHA nonetheless plays a supportive role, as it provides the structural foundation for healthy neuronal signal transmission. A balanced intake of both fatty acids — EPA and DHA — is considered sensible. For more on this topic, see our article Omega-3 and Mood.

DHA and eye health

The retina of your eye is the second tissue in the body in which DHA is present in exceptionally high concentrations. The photoreceptors of the retina — the rods and cones with which you perceive light and distinguish colours — contain membrane discs that are particularly rich in DHA-containing phospholipids. DHA is structurally necessary there so that the light-sensitive rhodopsin molecules can move quickly enough within the membrane and respond to light signals.

EFSA has confirmed the health claim: 250 mg DHA per day contributes to the maintenance of normal vision. This statement applies to adults and is supported by clinical evidence. For infants, DHA is even more critical for normal eye development — in the first months of life, DHA is preferentially incorporated into the retina.

Regarding age-related macular degeneration (AMD), one of the most common causes of vision loss in old age, epidemiological studies show an inverse association between high fish consumption (as a proxy for DHA intake) and AMD risk. The AREDS2 study, one of the largest randomised trials on eye health, examined omega-3 supplements in existing AMD — results here were mixed. Research is ongoing. For everything you need to know about the relationship between omega-3 and vision, see our article Omega-3 for the Eyes.

DHA during pregnancy and childhood

Foetal brain development

During pregnancy, DHA actively crosses the placenta and accumulates in the developing foetal brain. The need is particularly high in the third trimester, when the baby's brain is growing most rapidly and requires a large amount of DHA for building neural structures. This active transport takes priority over other nutrients — but it also means that with insufficient intake, the mother herself can suffer from DHA deficiency while reserves are used to supply the child.

EFSA recommends that pregnant women take an additional 200 mg DHA per day on top of the standard recommendation of 250 mg EPA+DHA daily — totalling at least 450 mg DHA per day during pregnancy. This recommendation is based on evidence that maternal DHA intake supports the normal brain and eye development of the foetus and infant.

Several cohort studies have shown that children of mothers with high DHA intake during pregnancy achieve better results in early developmental tests. A study by the University of Kansas followed children until the age of five and found measurable differences in cognitive tests in favour of the group with higher prenatal DHA intake.

DHA in breast milk

Breast milk contains DHA in concentrations that depend directly on the mother's diet. DHA content in breast milk varies considerably internationally: in fish-eating populations (Japan, parts of Scandinavia), the DHA proportion is significantly higher than in Western countries with low fish consumption. The WHO recommends that breast milk should contain at least 0.2 to 0.3 per cent of total fat content as DHA — a level that mothers with typical Western diets often do not reach without supplementation.

Breastfeeding mothers should therefore ensure adequate DHA intake. The EFSA recommendation of an additional 200 mg DHA applies during breastfeeding as well. High-quality fish oil or algae oil supplements can be a practical and safe solution here.

DHA for children and adolescents

Even after breastfeeding, DHA remains relevant for brain development. The brain grows and matures until early adulthood — myelination (the formation of the insulating sheath around nerve fibres), neuroplasticity, and the development of the prefrontal cortex continue until approximately age 25. Throughout this entire period, a continuous supply of DHA is advisable. Children who eat little fish are particularly at risk of deficiency. Algae oil-based supplements for children are a safe vegan alternative. For further background information, see our article Omega-3 during Pregnancy.

DHA content of key food sources

Source	DHA (mg/100 g)	Typical serving	DHA per serving
Salmon (Atlantic, wild)	~1,400 mg	150 g	~2,100 mg
Herring	~1,000 mg	150 g	~1,500 mg
Mackerel	~1,100 mg	150 g	~1,650 mg
Sardines (in oil)	~1,000 mg	100 g	~1,000 mg
Tuna (tinned, in water)	~200 mg	100 g	~200 mg
Algae oil (high-concentrate)	~15,000–20,000 mg	5 ml (1 tsp)	~750–1,000 mg
Breast milk (Western diet)	~50–100 mg	150 ml	~75–150 mg
Linseed oil	0 mg	—	0 mg

Figures are indicative; DHA content varies depending on origin, processing, and season. Sources: USDA Food Data Central, EFSA Scientific Opinion on DHA.

DHA sources: fish, fish oil, and algae oil

Sea fish is evolutionarily the most natural and efficient DHA source for humans. Oily fish such as salmon, mackerel, herring, and sardines can cover the DHA requirement for several days with a single serving. The German Nutrition Society (DGE) therefore recommends at least one serving of oily sea fish per week.

However, fish is not the original DHA source — that distinction belongs to microalgae. Fish accumulate DHA because they eat algae or animals that eat algae. This insight has led to algae oil now being available as a direct DHA supplement. Algae oil is biochemically identical to the DHA from fish oil, but contains no heavy metals (as algae come from controlled cultivation) and is completely vegan.

Purely plant-based ALA sources such as linseed oil, chia seeds, or walnuts contain no preformed DHA. The conversion rate of ALA to DHA in humans is below 1 per cent — for this reason, plant-based sources alone cannot meet DHA requirements. Anyone who does not eat fish should definitely use algae oil. For more on evaluating the quality of omega-3 products, see the Buyer's Guide to Omega-3 Oils.

How much DHA do I need daily?

The EFSA recommendation for adults is: at least 250 mg DHA per day (together with EPA) for the standard EFSA health claims. In practice, this means for most people:

• Adults (general): 250 mg DHA + EPA per day
• Pregnant women: 250 mg EPA+DHA plus an additional 200 mg DHA = at least 450 mg DHA daily
• Breastfeeding women: same recommendation as for pregnant women
• Infants (0–12 months): 100 mg DHA/day is considered adequate
• Children (1–2 years): 150 mg DHA/day

For specific health goals — such as high physical activity, certain medical conditions, or elevated cardiovascular risk — higher amounts may be appropriate, but this should always be discussed with a doctor or registered dietitian. Use our Omega-3 Requirements Calculator for initial guidance on your individual situation. A comprehensive overview of all relevant dosage recommendations can be found on the Dosage overview page.

DHA for vegans: algae oil as the solution

Anyone following a vegan or vegetarian diet faces a clear challenge: all significant dietary DHA sources are of animal origin. Linseed oil, hemp oil, and other plant-based oils contain ALA but no DHA — and the conversion in the body is, as described, minimal.

Algae oil fills this gap completely. It is produced from DHA-rich microalgae species (usually Schizochytrium or Crypthecodinium cohnii), which are cultivated in controlled fermentation facilities. The resulting DHA is chemically identical to that from fish oil. Additional advantages: no fishy odour, no heavy metal contamination, more ecologically sustainable production. The bioavailability of algae oil DHA is comparable to that of fish oil, as several bioavailability studies have shown — including a study by Arterburn et al. (2008), published in Prostaglandins, Leukotrienes and Essential Fatty Acids (PMID: 18589030).

For vegans, algae oil is therefore not merely an alternative to fish oil — it is the biologically cleanest and most direct DHA source available. Anyone who does not consume seafood or fish should use a high-quality algae oil supplement to reliably meet their daily DHA requirements.

Frequently asked questions about DHA