A team led by Katherine L. Tucker, PhD, director and professor of the Nutritional Epidemiology Program at the Friedman School of Nutrition Science and Policy at Tufts, studied a group of Boston-area men who were members of the ongoing Normative Aging Study (NAS). Tucker and her colleagues found that men who obtained more folate in their diets showed significantly less of a decline in verbal fluency skills over the course of three years than did men with lower dietary folate intake.
High folate levels, both in the diet and in the blood, also appeared to be protective against declines in another category of cognitive skills known as spatial copying. To test this, the 50- to 85-year-old study participants were asked to copy various shapes and figures, and their drawings were assessed for accuracy. "The men took a series of cognitive tests at the beginning of the study period and then repeated those tests three years later," explained Tucker. "We compared their first and second scores, reviewed their responses to dietary questionnaires, and took blood samples in order to see if nutrient levels in the diet and the blood were related to changes in cognitive performance."
In an earlier study with the same NAS group, which corroborated the findings of other investigators, the Tufts research team observed that high homocysteine--a known blood marker of cardiovascular disease risk--was associated with lower cognitive test scores.
Since folate supplementation can help reduce blood levels of homocysteine, it was thought that this might explain folate's beneficial effects. However, in the current study, the effects of folate were independent of its impact on homocysteine, which turned out to be more strongly associated with tests of memory.
"Unlike our prior work with this population, in which we observed an association between low folate levels and lower cognitive test scores at one point in time, this study looks at the effects of these nutrients over time." Tucker says, "That is an important step in establishing causality."
Tucker KL, Qiao N, Scott T, Rosenberg I, Spiro A, III. American Journal of Clinical Nutrition. 2005; 82: 627. "High homocysteine and low B vitamins predict cognitive decline in aging men: the Veterans Affairs Normative Aging Study."