London, Dec 19: A daily dose of vitamin B can dramatically combat memory loss in old age and even protect against Alzheimer's, a study has found.
People taking the pill had lower levels of a brain protein known to lead to a rise in the risk of dementia.
Researchers found it also slowed mental decline in older people who have slight problems with their memory.
More than 800,000 people in Britain suffer from dementia and the number is forecast to double within a generation, but previous drug trials have been unsuccessful.
Around a sixth of people over 70 are thought to suffer from mild cognitive impairment and about half develop dementia, usually within five years of diagnosis.
The research suggested dementia could be treated with a food supplement rather than by taking complicated medicines.
More than 250 people took part in the study, at Oxford University, including people with mild cognitive impairment who were aged 70 years or older.
They were given vitamin B - found naturally in food such as beans, meat, wholegrains and bananas - or a placebo over a two-year period.
Taking the food supplement appeared to help maintain mental processes, such as planning, organising and recalling information.
An earlier study showed B vitamins slowed the rate of brain shrinkage compared with a group receiving a placebo.
Dr Carrie Ruxton of the Health Supplements Information Service told the Daily Express: 'The findings from these two reports should be of interest to clinicians.'