LOWER and higher levels of vitamin B12 within the currently accepted normal range are both associated with neurological changes in healthy older adults, a new study found.
Vitamin B12 is essential for metabolism and neurological function, and while its deficiency is well established as a cause of neurological impairment, the precise threshold for adequacy remains unclear. The study aimed to determine whether variations in B12 levels within the normal range are linked to measurable neurological effects, with potential implications for revising nutritional recommendations.
A total of 231 healthy older adults were recruited, with a median age of 71.2 years and a median B12 blood concentration of 414.8 pmol/L. Neurological function was assessed using multifocal visual evoked potential testing, processing speed evaluation, and magnetic resonance imaging. Serum biomarkers of neuroaxonal injury, astrocyte activation, and amyloid pathology were also measured. Analysis showed that lower levels of active B12 (holo-transcobalamin) were significantly associated with delayed visual evoked potentials (estimate: -0.04; p=0.023), slower processing speed (β=-2.39; p=0.006), and increased white matter hyperintensities on MRI (β=-0.21; p=0.039). Additionally, high levels of holo-haptocorrin, a biologically inactive form of B12, were correlated with increased serum Tau (β=0.22; p=0.015), a known biomarker of neurodegeneration.
These findings suggest that both insufficient and excessive levels of B12 within the normal range may contribute to neurological alterations in ageing individuals. Given the widespread use of B12 supplementation and the potential risks of both deficiency and excess, this study highlights the need for a reassessment of current guidelines for optimal B12 levels. In clinical practice, personalised B12 monitoring could help prevent neurological dysfunction in older adults by ensuring that levels are maintained within a range that supports cognitive and neural health.
Jenna Lorge, EMJ
Reference
Beaudry-Richard A et al. Vitamin B12 levels association with functional and structural biomarkers of central nervous system injury in older adults. Ann Neurol. 2025;DOI:10.1002/ana.27200.
