A recent study led by researchers from the University of California, San Francisco (UCSF), has revealed that maintaining the minimum recommended levels of vitamin B12 may not be sufficient, especially for older individuals. The research, published in Annals of Neurology on February 10, suggests that even within the “normal” range, low B12 concentrations can lead to neurological and cognitive impairments.
The study, spearheaded by Dr. Ari J. Green of UCSF’s Departments of Neurology and Ophthalmology, and the Weill Institute for Neurosciences, focused on older, healthy adults who displayed lower but still considered normal levels of B12. The findings revealed that participants with these levels exhibited damage to the brain’s white matter—the nerve fibers responsible for communication between brain regions—and slower cognitive and visual processing speeds when compared to those with higher B12 levels.
Dr. Green and his colleagues argue that these results challenge current vitamin B12 guidelines, raising questions about the adequacy of the existing recommendations. “Previous studies may have overlooked subtle cognitive and neurological manifestations linked to B12 levels that don’t cause overt symptoms,” said Dr. Green. He emphasized the need to redefine B12 deficiency criteria, incorporating functional biomarkers, to potentially prevent cognitive decline before it becomes clinically apparent.
The study involved 231 participants, all aged 71 on average, who were free from dementia or mild cognitive impairment. Their blood levels of B12 averaged 414.8 pmol/L, significantly higher than the U.S. minimum threshold of 148 pmol/L. The researchers focused on the biologically active form of B12, which more accurately reflects the vitamin available for the body’s use.
Participants with lower active B12 levels performed worse on cognitive tests, showing slower processing speeds and delayed responses to visual stimuli—indicators of subtle cognitive decline. MRIs also revealed a higher volume of white matter lesions, which are linked to cognitive decline, dementia, and stroke. These issues were particularly pronounced in older participants, suggesting that aging may exacerbate the impact of low B12.
While the study primarily targeted older adults, co-first author Alexandra Beaudry-Richard, MSc, noted that the effects of low B12 could be more widespread than previously thought. “These lower levels might affect cognition in ways we have not fully understood, potentially impacting a broader segment of the population than we realize,” she said.
The findings highlight the importance of reassessing B12 deficiency criteria and consider potential interventions to protect against cognitive decline, especially in older individuals.
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