The study, conducted by the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, found that among seniors with adequate vitamin B-12 levels, high levels of blood folate were associated with better cognitive function. Among seniors with low B-12 levels, however, scores on tests of cognitive function actually decreased with increasing folate levels.
"For seniors, low vitamin B-12 status and high serum folate was the worst combination," said Martha Savaria Morris, one of the study's authors.
The researchers studied data on people over the age of 60 from the National Health and Nutrition Examination Survey, conducted between 1999 in 2002. Cognitive function was measured by tests of response speed, attention span, visual spatial skills, associative learning and memory.
Morris cautioned that the study did not allow researchers to draw conclusions about causation. She also noted that high levels of folate in the blood may come from high intake, poor absorption or both.
"Our findings support the often-expressed idea that many seniors would benefit from more folate," said senior author Jacob Selhub, "but the research shows that we must look at the effects this would have on seniors with age-related vitamin B-12 deficiency .... There are also indications that too much folic acid and too little B-12 is a general phenomenon that affects other systems in the body, and might be a factor in some other diseases."
Holistic nutritionist Mike Adams, author of "The Seven Laws of Nutrition," emphasized that folate and vitamin B-12 intake is not just important for seniors.
"Nutrition greatly impact brain function in people of all ages," he said. "Boosting intake of folic acid and vitamin B-12 through nutritional supplements is a very effective and important way to maintain peak brain function."
###