ALZHEIMER'S patients may not benefit from eating fish despite its reputation as a "brain food," according to a new study.
Research has shown that while a fish-based diet could reduce the chances of getting the disease, or prevent its progress from a very early stage, further work is needed.
Scientists in the US carried out two investigations into DHA, an omega-3 fat
ty acid found in oily fish. Previous studies have indicated that fish oil rich in omega-3 can protect the brain from age-related dementia. However, the new study has cast doubt on the claims.
The first trial, the Alzheimer's Disease Co-operative Study (ADCS), was publicly funded and lasted 18 months.
It compared the effects of DHA and a dummy placebo on 402 volunteers with an average age of 76 who had been diagnosed with mild to moderate Alzheimer's.
But at the end of the study period there was no evidence that omega-3 supplements improved participants' memory and mental performance scores.
For the six month-long second trial, a DHA manufacturer tested one of its products on a group of 485 healthy people.
The study found an improvement in one test of memory and learning, but the participants did not have Alzheimer's or any other form of dementia.
Both sets of findings were presented yesterday at the International Conference on Alzheimer's Disease (ICAD) in Vienna.
Dr Joseph Quinn, from Oregon Health and Sciences University, who led the ADCS study, said: "These trial results do not support the routine use of DHA for patients with Alzheimer's."
However, there was some evidence that DHA might help people with a particular genetic make-up.
Dr Simon Ridley, research manager at the Alzheimer's Research Trust, said: "These studies show that using omega-3 fatty acids as a treatment late on may not be effective against Alzheimer's.
"But with previous population studies suggesting that fish oils could reduce dementia risk, getting oily fish, such as mackerel, herring, salmon and sardines into our weekly menus could still be good advice.
"This shouldn't spell the end of research into omega-3, however. It could be that omega-3 given very early in the disease process could make a difference, but for that to happen we must drive forward studies that improve our methods of diagnosing Alzheimer's disease."
Dr William Thies, chief medical and scientific officer at the Alzheimer's Association, said: "These two studies – and other recent Alzheimer's therapy trials – raise the possibility that treatments for Alzheimer's must be given very early in the disease for them to be truly effective.
"For that to happen, we need to get much better at early detection of Alzheimer's."
Around 700,000 people in the UK suffer from dementia, more than half of whom have Alzheimer's.
