Vitamin B12 is essential for making DNA, red blood cells, and nerve tissue. Although B12 deficiency is known to cause neurological problems, the exact level needed to prevent such issues is unclear.
This study by UC San Francisco researchers aimed to determine whether normal B12 levels in healthy older adults might still be linked to neurological damage or dysfunction.
The study suggests that meeting the minimum requirement for vitamin B12 might not be sufficient, especially for older adults, and could increase the risk of cognitive impairment.
Researchers found that older, healthy individuals with lower, yet normal, levels of B12 exhibited signs of neurological and cognitive deficiency. These lower B12 levels were linked to more damage to the brain’s white matter and lower test scores for cognitive and visual processing speeds than individuals with higher B12 levels.
Senior author Ari J. Green, MD, of the UCSF Departments of Neurology and Ophthalmology and the Weill Institute for Neurosciences said, “The results raise questions about current B12 requirements and suggest the recommendations need updating.”
The study enrolled 231 healthy elderly volunteers, aged 71, with a median B12 blood concentration of 414.8 pmol/L. They performed multifocal visual evoked potential testing, processing speed testing, and magnetic resonance imaging to assess neurological status. Moreover, they measured serum biomarkers of neuroaxonal injury, astrocyte involvement, and amyloid pathology.
The participants’ average blood B12 level was 414.8 pmol/L, much higher than the U.S. minimum of 148 pmol/L. Researchers adjusted for age, sex, education, and cardiovascular risks and focused on biologically active B12, which is a more accurate measure of usable vitamin B12 in the body.
Cognitive tests showed that participants with lower active B12 levels had slower processing speeds, indicating subtle cognitive decline. This effect was stronger in older participants. They also had significant delays in responding to visual stimuli, suggesting slower visual processing and brain activity.
MRI scans revealed more lesions in the participants’ white matter, which could be linked to cognitive decline, dementia, or stroke.
Co-first author Alexandra Beaudry-Richard, MSc, said, “The study volunteers were older adults who may have a specific vulnerability to lower levels of B12. These lower levels could “impact cognition to a greater extent than what we previously thought, and may affect a much larger proportion of the population than we realize.”
“Besides redefining B12 deficiency, clinicians should consider supplementation in older patients with neurological symptoms even if their levels are within normal limits. Ultimately, we need to invest in more research about the underlying biology of B12 insufficiency since it may be a preventable cause of cognitive decline.”
Journal Reference:
- Alexandra Beaudry-Richard, Ahmed Abdelhak et al. Vitamin B12 Levels Association with Functional and Structural Biomarkers of Central Nervous System Injury in Older Adults. Annals of Neurology. DOI: 10.1002/ana.27200
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