'Fish oil can help protect the ageing brain'

Eating fish can help keep your brain young, say scientists after finding that diets lacking omega-3 fatty acids hastens brain shrinkage and mental decline.

Researcher at the University of California, Los Angeles, found that people who eat the least amount of omega-3 fatty acids, a key nutrients found in fish oil, had less brain mass -- equivalent to about two years of chronological ageing.

It's already known that low levels of omega-3 fatty acids are associated with poor scores for visual memory, problem solving, multi-tasking and abstract thinking.

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.

In the new study, published in the journal Neurology, the researchers carried out brain scans of over 1,500 people with an average age of 67.

They found a greater rate of brain shrinkage in those who lacked docosahexaenoic acid (DHA), an omega-3 fatty acid that is thought to help nerve cells communicate with each other.

"People with lower blood levels of omega-3 fatty acids had lower brain volumes that were equivalent to about two years of structural brain ageing," lead researcher Dr Zaldy Tan was quoted as saying by the Daily Mail.

The study involved magnetic resonance imaging (MRI) brain scans and tests for mental function and omega-3 fatty acids in red blood cells. Participants whose DHA levels were among the bottom 25 per cent had smaller brains than those with higher DHA levels.

According to the researchers, the best dietary source of omega 3 fatty acids is oily fish because the human body cannot produce omega-3 fatty acids. 

There has been an explosion in the number of foods fortified with omega-3 oils, such as chickens, margarine, eggs, milk and bread, but they contain only small amounts.

Types of fish that contain high levels include tuna, salmon, mackerel, herring, sardines, and anchovies. 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.

Dr Marie Janson at British charity Alzheimer's Research UK said: "There has been a lot of research into the effects of omega 3, and this study will add to that debate.

"One strength of this study is that it used blood samples to measure people’s dietary intake of omega 3, rather than relying on answers to questionnaires to assess the link between omega 3 and cognition.

"However, this research does not tell us whether the people studied got worse or better over time. We would need to see large-scale, long-term studies before we can know whether a diet high in omega 3 can protect against dementia, and people shouldn't fill their freezers with oily fish just yet."