- Research shows people with higher levels of the omega-3 fatty acids found in fish oil may also have larger brain volumes in old age
- This would be the equivalent to preserving one or two years of brain health
They found people with higher levels of the omega-3 fatty acids found in fish oil may also have larger brain volumes in old age.
This would be the equivalent to preserving one to two years of brain health, says a new study published in the journal Neurology.
Shrinking brain volume is a sign of Alzheimer's disease as well as normal aging.
Britons are currently advised to eat fish at least twice a week, including one portion of oily fish.
One of the key omega-3 fatty acids is docosahexaenoic acid (DHA), which is thought to help nerve cells communicate with each other.
The richest source of the nutrient is oily fish, such as herring, mackerel and sardines.
For the US study, levels of omega-3 fatty acids including DHA in red blood cells were tested in 1,111 women who were part of the Women's Health Initiative Memory Study. Eight years later, when the women were aged around 78, MRI scans were taken to measure their brain volume.
Those with higher levels of omega-3s had larger total brain volumes eight years later.
Those with twice as high levels of fatty acids (7.5 vs. 3.4 per cent) had a 0.7 per cent larger brain volume, with the increase measuring up to two inches (6cm).
Study author James Pottala, of the University of South Dakota in Sioux Falls and Health Diagnostic Laboratory Inc. in Richmond, Virginia, said lower levels of fatty acids were linked to smaller-sized brains.
He said: 'These higher levels of fatty acids can be achieved through diet and the use of supplements, and the results suggest that the effect on brain volume is the equivalent of delaying the normal loss of brain cells that comes with aging by one to two years.'
Those with higher levels of omega-3s also had a 2.7 per cent larger volume in the hippocampus area, the brain's key memory centre.
In Alzheimer's disease, the hippocampus begins to shrink even before symptoms appear.
Dr Pottala said: 'Our study suggests that a higher tissue reserve of omega-3 fatty acids may slow the loss of cognitive function that can accompany brain atrophy.
'It adds to growing literature suggesting that higher omega-3 tissue levels, which can be achieved by dietary changes, may hold promise for delaying cognitive ageing and/or dementia.' The best dietary source of omega 3 fatty acids is oily fish because the human body cannot produce omega-3 fatty acids.
White fish is also a healthy food including cod, haddock and plaice although it contains lower levels of essential fatty acids.
Fish oil supplements are recommended as protection against heart attacks and sudden death, with regular fish eaters a third more likely to survive a heart attack.
Omega-3 fats work in several ways to reduce heart attack risk by cutting blood fats, reducing the chances of a blood clot and blocking dangerous heart rhythms that might otherwise prove fatal.
It is thought that omega-3 fatty acids in fish oils may reduce inflammation of the brain and play a part in brain development and nerve cell regeneration.
Dr Laura Phipps of Alzheimer's Research UK charity, said: 'There has been mixed evidence as to the benefits of omega-3 fish oils on the brain and whether they may protect against memory decline and dementia.
'This study suggests that higher levels of omega-3 fatty acids in blood are linked to larger brain size but the possible reasons for this association need further investigation. 'We know that the brain gets smaller in people with dementia, but it is unclear from the study what effect larger brain size would have on memory and thinking in the volunteers or their long-term risk of developing dementia.
'The best way to assess whether omega-3 could protect against dementia is through clinical trials and so far, trials of omega-3 supplementation have not shown benefits in protecting against cognitive decline.'
Dr Doug Brown of the Alzheimer's Society, said: 'It's interesting to see that eating more fish could lead to larger brain volume, particularly in the hippocampus - an area of the brain that comes under attack in dementia.
'We know that brain shrinkage can be linked to dementia and larger brain volumes could indicate a better ability to cope with the ravages of the condition, but it's a big leap to draw this conclusion.
'Whilst interesting, this study still leaves us in the dark about what effect eating fish has on the development of dementia.'