Eating three times more salt than recommended each day could cause changes in the brain linked to dementia, a study suggests.
Researchers found feeding mice an extremely salty diet caused the build-up of a protein called tau in the brain.
Tau, which helps nerve cells maintain their proper shape as well as transporting nutrients, is thought to play a role in Alzheimer’s.
The mice also performed worse on tests of their cognitive abilities, according to experts at Weill Cornell Medical College in New York.
However, the team has warned further studies are needed to prove a high-salt diet may cause this same effect in humans.
The NHS recommends adults consume no more than 6g of salt a day, or around one teaspoon, which contains around 2.4g of sodium.
Eating triple the recommended amount of salt may cause changes in the brain linked to dementia, a US study in mice has found
A diet high in salt can also cause raised blood pressure, which can increase the risk of heart disease and strokes.
The study may also offer another explanation as to why salty diets have been linked to dementia – other than through raising blood pressure.
Two-month-old mice were fed eight per cent sodium throughout the day for the 36-week study. It was pumped into their chow.
By comparison, mice normally consume less than one per cent of sodium on a daily basis, researchers wrote in the journal Nature.
The amount of sodium the trial mice consumed would be the equivalent of a human eating up to five times an adult’s recommended daily limit.
The team conducted brain scans on the animals throughout the research to monitor how the tau changed in their brains.
They noticed the protein began to accumulate at the four-week mark and continued to elevate throughout the study.
At 12 weeks the mice began struggling to recognise objects and found it difficult to remember pathways in maze tests.
WHAT IS DEMENTIA? THE KILLER DISEASE THAT ROBS SUFFERERS OF THEIR MEMORIES
A GLOBAL CONCERN
Dementia is an umbrella term used to describe a range of progressive neurological disorders, that is, conditions affecting the brain.
There are many different types of dementia, of which Alzheimer’s disease is the most common.
Some people may have a combination of types of dementia.
Regardless of which type is diagnosed, each person will experience their dementia in their own unique way.
Dementia is a global concern but it is most often seen in wealthier countries, where people are likely to live into very old age.
HOW MANY PEOPLE ARE AFFECTED?
The Alzheimer’s Society reports there are more than 850,000 people living with dementia in the UK today, of which more than 500,000 have Alzheimer’s.
It is estimated that the number of people living with dementia in the UK by 2025 will rise to over 1 million.
In the US, it’s estimated there are 5.5 million Alzheimer’s sufferers. A similar percentage rise is expected in the coming years.
As a person’s age increases, so does the risk of them developing dementia.
Rates of diagnosis are improving but many people with dementia are thought to still be undiagnosed.
IS THERE A CURE?
Currently there is no cure for dementia.
But new drugs can slow down its progression and the earlier it is spotted the more effective treatments are.
Source: Alzheimer’s Society
Results also showed the mice has suffered narrowing of the small blood vessels deep inside their brains, preventing nutrients from being transported between cells – another sign of vascular dementia.
Co-lead author Professor Costantino Iadecola said: ‘The results identify a previously unknown pathway linking dietary habits and cognitive health.
‘They indicate that avoiding high-salt diets could maintain cognitive function.
‘Our data provide a previously unrecognised link between dietary habits, vascular dysfunction and tau pathology.’
Despite the study proving salty diets cause the build-up of tau, experts have issued caution over the findings.
Dr Evangeline Mantzioris, programme director of nutrition and food sciences at the University of South Australia, said the salt intake of mice was incredibly high.
She added that mice offer a ‘good biological equivalent’ to humans – but ‘we cannot with certainty say the same effect would happen in humans’.
However, she praised the ‘important’ research – the first to prove salt can damage blood vessels and cause a build-up of tau in the brain.
Professor Clare Collins, of The University of Newcastle, said the research offers more reason to cut out salt from diet.
Professor John Funder, a neuroscientist at the University of Melbourne, said normal mouse chow would still be a high salt intake in humans.
‘Any extrapolation from mice on a salt intake of eight per cent to the human situation may be cute, but it is grossly irresponsible in terms of science,’ he added.
Dementia strikes an estimated 850,000 people in the UK – a figure set to rise to two million by 2050 because of the ageing population.
With no cure in sight there is increasing focus on lifestyle changes that can protect against the disease – such as eating healthier foods and doing more exercise.
The Alzheimer’s Society says a good diet is an important factor in reducing the risk of dementia.
It advises people to look out for hidden salt in foods – and consume plenty of fruit, vegetables and oily fish and less saturated fat.
‘HOW DID THE RESEARCHERS COMPARE THE COGNITIVE ABILITIES OF THE MICE?’
The novel object recognition test (NOR) test was conducted under dim light in a plastic box.
Plastic objects that varied in colour and shape but had similar sizes were used. A video camera mounted on the wall directly above the box was used to record the test.
Mice were put in the box for one full day before the test to let them acclimatise to their new surroundings.
Two identical sample objects were then added to the box, which the mice were allowed to inspect for five minutes.
A day later, mice were placed in the same box but one of the two objects was replaced by a new object that differed slightly.
Exploration of an object was defined as the mouse sniffing the object or touching the object while looking at it.
The amount of time taken to explore the novel object was expressed as a percentage of the total exploration time and provides an index of recognition memory.
Mice which were on the high-salt diets took more than a fifth longer to familiarise themselves with the objects compared to rodents on a normal diet.
The other cognitive test, known as the Barnes maze, consisted of a circular open surface that was 90 cm in diameter.
There were 20 circular holes equally spaced around the perimeter. On each trial a mouse was placed into a start tube located in the centre of the maze, the start tube was raised, and the buzzer was turned on until the mouse entered the escape hole.
For each trial mice were given three minutes to locate the escape hole, after which they were guided to the escape hole or placed directly into the escape box if they failed to enter it.
Mice on the high-salt diet took up to three times longer than healthy ones to complete the maze. Some did not finish it at all.
First drug ‘that can SLOW Alzheimer’s is ready to bring to market after ‘promising trials’, company claims
The first treatment to slow Alzheimer’s disease could soon be available to millions, it was dramatically announced last night.
Drugs giant Biogen shook the medical world by unexpectedly releasing results suggesting it has developed the first effective medicine for the disease.
After years of high-profile dementia trial failures, experts last night welcomed the ‘transformative discovery’ as a ‘hugely exciting’ breakthrough that could be life changing for dementia patients.
Crucially, the company said trial data for drug aducanumab is strong enough to apply for medicine licences in the US, Europe and Japan early next year. That in itself is a huge milestone.
Despite billions of pounds spent on research, no company has got to the point of submitting an application to drugs regulators before.
Biogen said results from more than 3,000 people with Alzheimer’s showed aducanumab led to a significant slowing of the disease’s progression.
CEO Michel Vounatsos said the company had already received encouragement from US regulator the Food and Drugs Administration.
‘We got clear support from the FDA,’ he said. ‘With such a devastating disease that affects tens of millions worldwide, today’s announcement is truly heartening in the fight against Alzheimer’s.’
If the applications are successful the medicine could be available within two years – a prospect that saw Biogen shares soar 35 per cent yesterday, adding $14.9billion (£11.6billion) to the company’s market value.
It would be the first real treatment for Alzheimer’s disease, which affects 500,000 in Britain and tens of millions more around the world. Although drugs are available that control certain symptoms for short periods, no new treatment has been approved for 15 years, and there are no drugs at all that target the underlying cause of Alzheimer’s.
Aducanumab changes that by targeting ‘amyloid beta’ – a toxic protein which causes plaques to build up in the brain. These plaques, or clusters of amyloid protein, interfere with the function of brain cells.