New Study Shows that a B-vitamin Deficiency May Spawn Vascular Cognitive Impairment

How does your B-vitamin intake stack up? Why should this be important to you and your loved ones? Well, according to a new study conducted Researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts University, a deficiency of certain B-vitamins may wind up causing vascular cognitive impairment,

In the Tuft’s study, mice were used as to explore the metabolic, cognitive, and microvascular impact of a dietary B-vitamin deficiency.

"Metabolic impairments induced by a diet deficient in three B-vitamins -folate, B12 and B6- caused cognitive dysfunction and reductions in brain capillary length and density in our mouse model," says Aron Troen, Ph.D., the study's lead author and an assistant professor at Tufts University's Friedman School of Nutrition Science and Policy. "The vascular changes occurred in the absence of neurotoxic or degenerative changes."

Dr. Troen went on to explain that "Mice fed a diet deficient in folate and vitamins B12 and B6 demonstrated significant deficits in spatial learning and memory compared with normal mice." The Tuft’s team noted similar but less pronounced differences between normal mice and a third group of mice that were fed a diet enriched with methionine.

Troen and his colleagues took mice and divied them into three groups which were fed a different diet for 10 weeks. The control (or comparison) group was fed a normal diet containing methionine and B-vitamins, while mice in the other groups were put on diets designed to induce high homocysteine levels but through different metabolic means or mechanisms. One diet was methionine-enriched, and the other was deficient in B vitamins. Tuft scientists measured blood concentrations of B-vitamins and homocysteine and assessed the animal’s brain anatomy and blood vessels. They also evaluated psychomotor function by employing a battery of age-sensitive tests, such as holding on to a wire and walking a beam, and evaluated their spatial learning and memory using the Morris water maze, a well-validated and sensitive test of rodent cognitive function.

"It took longer, on average, for the B-vitamin-deficient mice to maneuver the water maze, compared with controls," reported Dr. Troen. "Longer latencies were associated with higher plasma homocysteine levels and shorter capillaries, particularly in the brain region called the hippocampus."

"The B-vitamin-deficient mice also developed plasma homocysteine concentrations that were seven-fold higher than the concentrations observed in mice fed a normal diet," added Dr. Troen. Homocysteine is created in the human body by the breakdown of methionine. Various B-vitamins including folate, vitamin B12, and vitamin B6, are needed to transform homocysteine back to methionine, which lowers serum (blood) levels of homocysteine.

Studies have linked elevations in plasma homocysteine with an increased risk for cognitive impairment. "However," Troen says, "it has not been determined that homocysteine is directly responsible. Based on the findings of our study, we theorize that a deficiency of B-vitamins induces a metabolic disorder that manifests with high homocysteine, as well as cerebral microvascular dysfunction."

Irwin Rosenberg, MD, director of the Nutrition and Neurocognition Laboratory at the HNRCA, had this to say:"The elevated levels of homocysteine that were associated with vascular cognitive impairment in the mice in our study are comparable to the levels that are associated in older adults with an increased risk for Alzheimer's disease and cerebrovascular disease, the latter of which manifests with conditions such as stroke and atherosclerosis. These findings may indicate that microvascular changes mediate the association between high homocysteine levels and human age-related cognitive decline."