More evidence that a diet rich in oily
fish and vegetables can reduce the chances of dementia
later in life has been uncovered by scientists.
Studies published in US journals suggested
that a "Mediterranean diet" or long-term beta-carotene
supplements could ward off the illness.
Both contain anti-oxidants, which could
protect the brain from damage.
The Alzheimer's Society said that most
people could cut their risk by eating a healthy diet.
The first study, in the journal Neurology,
looked at the diets of more than 8,000 healthy men and
women aged over 65.
They found that those who regularly ate
omega-3 oils, found in some cooking oils and certain types
of fish, were far less likely to develop dementia over
the following four year period.
People who ate fish at least once a week
had a 40% lower risk of dementia, while eating fruit and
vegetables once a day reduced the risk by 35%.
However, eating other types of cooking
oils containing omega-6 - such as sunflower oil - rather
than omega-3 doubled the risk.
Dr Pascale Barberger-Gateau, from the
French National Institute for Health and Medical Research
in Bordeaux, said: "These results could have considerable
implications for public health."
The second study looked at the effects
of beta-carotene supplements over an average of 18 years.
Mental testing
Beta-carotene is the chemical which gives
carrots their colour, and is thought to have beneficial
anti-oxidant properties.
The 4,000 volunteers took either a beta-carotene
pill or a "placebo" pill with no active ingredients every
other day.
Those who took the beta-carotene scored
significantly higher on mental tests - particularly on
"verbal memory".
Doing badly on these tests is believed
to be a sign that the person has a higher risk of dementia
in later life.
The reason why any of these foods or
supplements might ward off dementia is unclear.
But many experts suggest that anti-oxidants
can slow down the damage to the body's cells - including
brain cells - which is normally accumulated over a lifetime.
And there is also debate over whether
vitamin supplements are the best way to get anti-oxidants
into the body.
In an accompanying editorial, Dr Kristine
Yaffe of the University of California at San Francisco
said that other studies into beta-carotene supplements
had shown contrasting results, and the overall picture
did not justify their use to boost memory.
One study has even suggested that taking
beta-carotene long-term could be harmful.
Mediterranean
Susanne Sorensen, the Director of Research
for the Alzheimer's Society, said that it was possible
that those who were prepared to take a pill so reliably
over a long period might be more careful about their diet
than the average person, accounting for some of the difference.
However, she said people should realise
that there were steps they could take - such as adopting
a so-called "Mediterranean diet" - to cut their risk of
the illness.
She said: "The majority of the population
can reduce their risk by eating a diet rich in vegetables,
fruit and fish."
