DHA is incorporated into the phospholipid membranes of neurons, where it maintains membrane fluidity — essential for the rapid signalling between brain cells. Synaptic vesicles (which release neurotransmitters) are particularly enriched in DHA. Without adequate DHA, neurotransmission slows, synaptic plasticity is impaired, and neurons become more vulnerable to damage.
DHA also has direct neuroprotective properties: it's converted into specialised pro-resolving mediators (SPMs) like neuroprotectin D1 (NPD1), which actively resolve inflammation in the brain and protect neurons from apoptosis. Low DHA status is consistently associated with accelerated brain ageing, cognitive decline, depression, and increased Alzheimer's risk.
In pregnancy and infancy, DHA is critical for brain development — maternal DHA supplementation is associated with improved infant cognitive scores. In adulthood, higher DHA intake correlates with better cognitive performance, larger hippocampal volume, and reduced risk of depression.
In ageing, the Framingham Heart Study found that participants in the top quartile of DHA blood levels had a 47% lower risk of developing dementia. Higher DHA status is associated with slower brain atrophy, better memory, and maintained processing speed. While intervention trials in established dementia have shown limited benefit, prevention through lifelong adequate DHA intake appears strongly protective.
The primary dietary source is fatty fish: salmon, mackerel, sardines, and herring provide 1,000-2,000mg of combined EPA/DHA per serving. Eating fatty fish 2-3 times per week meets most people's needs. If you don't eat fish regularly, a quality fish oil supplement providing at least 500mg DHA daily is advisable.
Algae-based DHA supplements are available for vegetarians and vegans — algae is where fish get their DHA originally. ALA (from flaxseed and walnuts) can theoretically be converted to DHA, but the conversion rate in humans is less than 5%, making it an unreliable source. For brain health specifically, prioritise DHA over EPA — while both are valuable, DHA is the structural brain fatty acid. Choose supplements tested for mercury, PCBs, and oxidation.
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You are pregnant, breastfeeding, taking prescription medications, or have a pre-existing medical condition. This content is educational and does not replace professional medical advice.
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