A recent study published in the Annals of Neurology on February 10, 2025, investigated the relationship between vitamin B12 levels and brain health in older adults. The researchers found that even when vitamin B12 levels are within the normal range, lower concentrations can be linked to subtle brain changes and cognitive issues.

Key Findings:
Brain Structure Changes: Participants with lower B12 levels showed more damage in the brain’s white matter, which consists of nerve fibers connecting different brain regions. Such damage is often associated with cognitive decline, dementia, or stroke.
Cognitive Performance: Those with lower B12 levels performed slower on tests measuring thinking speed and visual processing.
Study Details:
Participants: 231 healthy individuals, average age 71, without dementia or mild cognitive impairment.
B12 Levels: The average B12 level was 414.8 pmol/L, above the U.S. minimum of 148 pmol/L.
Assessments: Blood tests measured active B12 levels, while cognitive tests evaluated thinking and visual processing speeds. Brain MRIs assessed white matter integrity.
Implications:
This study suggests that current definitions of adequate B12 levels might need revision, as even “normal” levels could be insufficient for optimal brain health in older adults. Clinicians might consider B12 supplementation for older patients showing neurological symptoms, even if their B12 levels are within the standard range.

In summary, maintaining higher vitamin B12 levels may be important for preserving brain health and cognitive function as we age.

This chart is showing that too little or too much B12 is bad. The problem, it’s difficult to optimize, need blood tests…

“Cobalamin, or vitamin B12 (B12), is an essential vitamin normally acquired through absorption in the enteric system in mammals. Deficiency in humans can be caused by a lack of intake (eg, vegan diet) or by any disease or procedure of the digestive tract impairing the absorption of B12.¹ After depletion of B12 stores, signs of deficiency such as hematological and neurological symptoms may develop, including megaloblastic anemia and subacute combined degeneration of the spinal cord.² The latter presents as a spinal syndrome (sensory ataxia, paresthesia, weakness, etc.) involving multiple tracts, principally the posterior columns.^2, 3“

“In addition to affecting general cognition and memory, vitamin B12 deficiency may even lead to dementia and psychosis, suggesting a broader dependence of the brain on B12.^8–11 Nonetheless, the VITACOG study established that B vitamin supplementation including B12 in older adults with mild cognitive impairment (MCI) leads to both functional and structural benefits.^12, 13 According to their foundational work, B12 supplementation slows the progression of brain atrophy in MCI and of clinical decline in multiple areas of cognitive testing. Moreover, B12 deficiency is associated with a higher burden of WM hyperintensities (WMH) in the brain, which could indicate microstructural changes (ie, ependymal disruption or chronic ischemic changes) reflecting overall brain health.^14–16“