Folic acid supplements can improve the memory and brain power of ageing brains, research shows.
Folic acid aided memory
Men and women aged 50 to 70 who took daily supplements had similar mental abilities to contemporaries almost five years younger, The Lancet study found.
But experts said this benefit must be balanced against other risks - an increase in folic acid can mask a vitamin B12 deficiency in older people.
This type of anaemia can cause serious health problems, like nerve damage.
Indeed, the Food Standards Agency recently said this risk should be taken into account should the UK want to routinely add folic acid to foods such as bread as a public health measure to prevent birth defects.
Currently only women planning to conceive are currently advised to take folic acid.
Both folic acid and vitamin B12 are essential for good health and good levels can be achieved by eating a healthy, balanced diet.
Green vegetables are rich in folic acid, while B12 is found in foods such as eggs and meat.
In the study, the Dutch researchers from the University of Wageningen gave a group of 818 volunteers either low dose folic acid supplements or a dummy drug for three years.
The folic acid group had significantly better memories and were faster at processing information, the researchers found.
Both abilities are known to decline with age, and loss of performance in these areas has been linked to a higher risk of dementia in the elderly.
Taking folic acid also led to a significant reduction in levels of homocysteine, a blood chemical linked both to heart disease and dementia.
Trials are under way to examine the effect of homocysteine-lowering on blood vessel disease and brain function.
The study authors, Dr Jane Durga, from the University of Wageningen in the Netherlands and colleagues at the Nestle Research Centre in Lausanne, Switzerland, said their work should be repeated in other populations, including people with dementia, to provide greater insight into the clinical relevance of folic acid supplementation.
Gordon Lishman of Age Concern said: "It is clear that further research is needed to try to reach a more definitive answer on the benefits, or not, of folic acid supplementation and more generally the introduction of folic acid into flour, which was recently recommended by the Food Standards Agency. Only this will enable more informed choices to be made."