We are not recommending at the moment that people should rush out and start taking folic acid

Dr Ross Taylor

But too much folic acid could impact on a person's vitamin B12 intake - which if it falls too low could, at worst, result in irreversible nerve damage.

The researchers acknowledge there is a "health dilemma" because no screening yet exists to predict who would be at risk of the vitamin deficiency.

The British Dietetic Association (BDA) says the study gives more information on what is already known about the benefits of folic acid for the elderly.

Benefit

But the BDA warned against taking folic acid supplements until improved screening is available for detecting a lack of vitamin B12.

Researchers looked at the benefit of folate (folic acid) which helps reduce the level of homocysteine, an amino-acid which can lead to vascular disease.

Dr Taylor: Study could have very important implications

Elderly people make up the greatest proportion of the population who suffer from heart disease complaints.

According to the Department of Health during 2000 heart disease claimed the lives of 27,964 people aged 65-74 in the UK.

Folic acid is found in high levels in foods such as bread, biscuits and breakfast cereals.

During the three-year survey 300 men and women aged 65-74 were tested in Aberdeen from two GP practices.

'Early days'

They were given folic tablets of varying strengths over a six-week period.

The researchers found that only those who took the highest levels of folate - between 400 and 600 micrograms - showed a recorded drop in their homocysteine levels.

Professor Michael Golden, who recently retired and led the study said: "This could have major implications because it is the elderly who bear the brunt of cardio-vascular problems.

Dr Ross Taylor, of the University of Aberdeen Medical School, who also worked on the study, said it indicated a need for three times the recommended intake.

Health benefits

Dr Taylor told the BBC: "We are not recommending at the moment that people should rush out and start taking folic acid - it is very early days although this may turn out to be quite important."

Dr Wendy Doyle, national spokesperson for the British Dietetic Association said: "The health benefits of taking folic acid are fairly obvious as long as the proper screening is there to detect deficiency of vitamin B12 to see what proportion of this age group were suffering from it."

The study was funded by the Wellcome Trust, an independent biomedical research charity and is published in the latest edition of the Quarterly Journal of Medicine.