Folic acid supplements may help improve the memory and brain power of people over 50, a new study suggests.

Cognitive function such as memory and processing information quickly declines with age and has been linked to risk of dementia in old age.

Previous researchers have suggested that low folate in the blood may be linked to poor cognitive performance.

To test the idea, Jane Durga of Wageningen University in the Netherlands and her colleagues at the Nestle Research Centre in Lausanne, Switzerland, randomly assigned 818 people between the ages of 50 and 70 to take 800 micrograms of folic acid or a placebo orally each day for three years.

The participants had low levels of folate before the experiment began.

"We have shown that three-year folic acid supplementation improves performance on tests that measure information processing speed and memory, domains that are known to decline with age," the researchers concluded in this week's issue of the journal The Lancet.

Memory tests showed some people performed as if they were seven years younger.

Those taking folic acid also showed a significant drop in levels of homocysteine, an amino acid in the blood linked to both heart disease and dementia.

Folate is a B vitamin that the body uses to make healthy new cells. It is found naturally in leafy green vegetables such as spinach, citrus fruits and beans. Dietary supplements offer the vitamin in the synthetic form of folic acid.

Experts caution that an increase in folate levels can also mask a deficiency in vitamin B12 in older people, which can lead to health problems such as nerve damage.

Researchers call for further study

The researchers called for their experiment to be repeated in other populations, such as those with dementia, to clarify the clinical importance of folic acid supplementation.

Researchers are also looking at whether lowering homocysteine levels affects heart disease and brain function. Folate, vitamin B12 and vitamin B6 help the body to process homocysteine.

Folate deficiency has also been linked to neural tube defects, in which the central nervous system fails to develop fully in the fetus, leading to defects such as spina bifida.

The Canadian government introduced mandatory fortification of whole-grain breads, cereals, flour, cornmeal and pasta with folic acid in 1998. Since then, the rate of birth defects such as spina bifida has declined.

European regulators do not allow folic acid supplementation in foods because of concerns over food additives.