- A two-year trial found that high-dose DHA fish oil supplements reached the brain but did not improve memory or cognition.
- The supplements also failed to slow shrinkage in the hippocampus, a brain region linked to memory and Alzheimer’s risk.
- The findings challenge the idea that fish oil tablets are a reliable way to protect brain health.
Fish oil supplements are often sold as brain protection in a capsule.
A new clinical trial suggests that claim deserves a lot more scepticism.
Researchers studied 365 adults aged 55 to 80 who rarely ate fish and were considered at increased risk of Alzheimer’s disease.
Nearly half carried the APOE4 gene, the strongest known genetic risk factor for late-onset Alzheimer’s.
Participants were randomly assigned to take either high-dose DHA fish oil or placebo for two years.
DHA is an omega-3 fatty acid involved in brain cell function.
The first question was whether the supplement actually reached the brain.
It did.
After six months, DHA levels in cerebrospinal fluid had increased by an average of 17%.
That means poor delivery was not the problem.
The issue was what happened next.
Despite reaching the brain, DHA supplementation did not improve memory or thinking test scores compared with placebo.
It also did not slow shrinkage of the hippocampus.
That is important because the hippocampus is central to memory and is commonly affected in Alzheimer’s disease.
The results do not mean omega-3 fats are useless.
They are important nutrients and oily fish can be part of a healthy diet.
But this trial does not support high-dose fish oil supplements as a way to prevent Alzheimer’s or protect memory in older adults at risk.
The researchers suggest omega-3s may work differently when consumed as part of an overall Mediterranean-style eating pattern.
That makes sense.
- High intake of fish improves children’s behaviour
- Eating oily fish lowers twice a week lowers chronic kidney disease risk
- High intake of fish oil could trigger heart complications and strokes
A diet is not just one nutrient.
It is a whole pattern of fats, fibre, plant foods, fish, minerals and metabolic effects.
The lesson is familiar but worth repeating.
Brain health is unlikely to be solved by a single supplement.
Sleep, exercise, blood pressure, glucose control, diet quality and overall vascular health probably matter far more than a fish oil capsule.
