It takes just a daily vitamin B pill to ward off Alzheimer’s disease, scientists have found.
A simple pill, which contains high doses of B vitamins and folic acid, could dramatically slow the onset of memory loss in old age – by as much as 70 per cent.
It may even prevent your brain from shrinking, which is a symptom linked to forgetfulness.
More than 800,000 people in Britain suffer from dementia and the number is forecast to double within a generation. Previous drug trials have been unsuccessful.
The recent findings mean in future, people could be tested for their vitamin B levels in middle age and recommended they alter their diet to boost their chances of remaining healthy.
However, people have bee warned they should not begin taking supplements without consulting their doctor because they can have a harmful impact on other conditions such as cancer.
A full scale national trial based on the research into vitamin B and Alzheimer’s will begin within the year.
Dr Celeste de Jager of Oxford University, who led the trial, said the trial had "definitively" shown that the vitamins were a good way of preventing mental decline.
Speaking at the British Science Festival, she said: "A lot of the time brain changes start in your forties and fifties before you get clinical symptoms.
"I would think that in middle age people should start thinking about their vitamin levels."
Asked if she would personally take the vitamins as a precaution against Alzheimer's, Dr de Jager said: "I would ask the doctor to check my B12 and my folic acid levels for starters.
"I take supplements when I'm feeling a bit low, I don't take one every day but I would certainly have multi-vitamins and B vitamins in my cupboard."
The study was carried out on 270 people aged 70 and above who suffered from lapses in memory known as mild cognitive impairment (MCI).
The condition affects 1.5 million people in Britain, or one in six people aged over 70, and half of all sufferers slip into dementia within five years of being diagnosed.
The new treatment targets a compound in the bloodstream called homocysteine which is produced naturally by the body but reaches higher levels in old age.
It damages the lining of blood vessels and leads to shrinkage of the brain, causing an increased risk of Alzheimer's as well as stroke and heart disease.
Half of patients were given pills containing extremely high doses of vitamins B6, B12 and folic acid, which are known to lower blood homocysteine levels, while the rest were given a placebo.
At several points during the study patients were given a simple verbal memory task in which they learnt a list of 12 words and required to recall them 20 minutes later.
After the first year, those with the highest levels of homocysteine were 70 per cent more likely to give a correct answer if they had been taking the vitamins than if they took the placebo.
There was little difference in memory rates between patients with below average levels of homocysteine regardless of which pills they took.
This indicated that normal amounts of the compound do not affect brain function.
Scans of patients' brains showed that the vitamin pills reduced shrinkage by 30 per cent on average, rising to 50 per cent among patients with high homocysteine levels.
"The higher the homocysteine level in the blood, the better the response was on treatment," Dr de Jager said.
"We need more research to show that we can actually delay the decline to dementia."
The doses of vitamins patients were given were far higher than those found in vitamin supplements or in food, she added.
