UCSF researchers found that older adults with lower, but still technically normal, B12 showed slower processing speeds, more white matter damage, and cognitive weaknesses.

When “Normal” Vitamin B12 May Not Be Enough
Meeting the standard daily requirement for vitamin B12, which is essential for making DNA, red blood cells, and nerve tissue, may not provide enough protection for the brain, particularly in older adults. In fact, falling within the “normal” range could still increase the risk of cognitive problems.

Researchers at UC San Francisco studied healthy older adults and discovered that participants with lower B12 levels, even though still considered normal, showed neurological and cognitive weaknesses. These individuals had more damage in the brain’s white matter (the network of nerve fibers that allows different regions of the brain to communicate) and scored lower on tests measuring cognitive speed and visual processing compared with those who had higher B12 levels.

The study was published in Annals of Neurology.

Rethinking Vitamin B12 Guidelines
According to senior author Ari J. Green, MD, of UCSF’s Departments of Neurology and Ophthalmology and the Weill Institute for Neurosciences, the results raise concerns about whether current B12 recommendations are sufficient and suggest that guidelines may need to be revised.

“Previous studies that defined healthy amounts of B12 may have missed subtle functional manifestations of high or low levels that can affect people without causing overt symptoms,” said Green, noting that clear deficiencies of the vitamin are commonly associated with a type of anemia. “Revisiting the definition of B12 deficiency to incorporate functional biomarkers could lead to earlier intervention and prevention of cognitive decline.”

Low B12, Slower Thinking, and Brain Lesions
In the study, researchers enrolled 231 healthy participants without dementia or mild cognitive impairment, whose average age was 71. They were recruited through the Brain Aging Network for Cognitive Health (BrANCH) study at UCSF.

Their blood B12 amounts averaged 414.8 pmol/L, well above the U.S. minimum of 148 pmol/L. Adjusted for factors like age, sex, education and cardiovascular risks, researchers looked at the biologically active component of B12, which provides a more accurate measure of the amount of the vitamin that the body can utilize. In cognitive testing, participants with lower active B12 were found to have slower processing speed, relating to subtle cognitive decline. Its impact was amplified by older age. They also showed significant delays responding to visual stimuli, indicating slower visual processing speeds and general slower brain conductivity.

MRIs revealed a higher volume of lesions in the participants’ white matter, which may be associated with cognitive decline, dementia, or stroke.

Study
https://doi.org/10.1002/ana.27200