"In 818 older adults, daily oral folic acid supplementation for three years beneficially affected global cognitive function, and specifically memory, and information processing: functions that are sensitive to ageing," wrote lead author Jane Durga in this week's issue of The Lancet.
Cognitive performance declines naturally with age, but the results of Folic Acid and Carotid Intima-media Thickness (FACIT) trial suggests that this could be slowed by folic acid supplementation.
The study randomly assigned the subjects between the ages of 50 and 70 to receive either a folic acid supplement (800 micrograms per day, Swiss-Caps Benelux) or placebo for three years.
Durga, currently with the Nestle Research Center in Lausanne, focussed on older men and women with average plasma total homocysteine concentrations of 13 micromoles per litre or more and vitamin B12 levels of at least 200 picomoles per litre.
Normal homocysteine levels are defined as between five and 15 micromoles per litre of blood, placing the study participants at the upper end of the 'normal' bracket.
Cognitive function was assessed using a battery of tests, including the word learning test, concept shifting test, stroop colour-word test, verbal fluency test, and the letter digit substitution test. Although not used for the study outcome, the researchers did use the mini-mental state examination to screen for possible dementia.
The researchers from Wageningen University and Wageningen Centre for Food Sciences, and University Hospital Maastricht, report: "Three-year folic acid supplementation confers an individual the performance of someone 4.7 years younger for memory, 1.7 years younger for sensorimotor speed, 2.1 years younger for information processing speed, and 1.5 years younger for global cognitive function."
They also report that delayed recall for the folic acid supplemented group was similar to a performance of someone 6.9 years younger.
"We have shown that 3-year folic acid supplementation improves performance on tests that measure information processing speed and memory, domains that are known to decline with age. [Our study was conducted] in older adults with raised total homocysteine concentrations," said the researchers.
The authors note a couple of limitations, including focussing on individuals with slightly raised levels of the amino acid homocysteine, previously linked to an increase in cognitive decline and dementia.
"Thus, the effect of folic acid supplementation might be greater than would be expected in populations with lower plasma total homocysteine concentrations - eg. in countries such as the USA , with mandated fortification of flour with folic acid," they said.
They also note that all of the participants had sufficient levels of vitamin B12. Vitamin B12 deficiency causes a form of aenemia in elderly people, and can cause dementia.
"Will folic acid supplementation lead to a reduced incidence of dementia?" asked Durga.
"Although folic acid improved performance on tests of memory, including delayed recall, additional research is needed to determine whether folic acid supplementation can reduce the risk of mild cognitive impairment or Alzheimer's disease," she said.
In an accompanying editorial, Martha Morris and Christine Tangney from Rush University Medical Center, Chicago, said the FACIT trial was "well-designed and unique in its approach of targeting individuals who might benefit from folate supplementation."
Morris and Tangney asked how these findings could correspond to the general population, and agreed with the Dutch researchers' call for more research.
"To make more informed dietary recommendations for optimum folate intake, we need randomised trials that take the approach of the FACIT trial," they said.
Source: The Lancet 20 January 2007, Volume 369, Pages 208-215 "Effects of 3-year Folic Acid Supplementation on cognitive function in older adults in the FACIT trial: A randomized, double-blind, controlled trial" Authors: J. Durga, P.J. van Boxtel, E.G. Schouten, F.J. Kok, J. Jolles, M.B. Katan, and P. Verhoef
Editorial: The Lancet 20 January 2007, Volume 369, Pages 166-167 "Is dietary intake of folate too low?" Authors: M.C. Morris, C.C. Tangney