A University of California San Francisco study has linked lower but still normal levels of active vitamin B12 to slower thinking and white matter damage in healthy older adults. The research, published in Annals of Neurology in 2025, suggests current guidelines may miss early neurological risks. Researchers examined 231 participants with an average age of 71.
The study focused on older adults without dementia or mild cognitive impairment. Participants had an average blood B12 level of 414.8 pmol/L, well above the U.S. minimum of 148 pmol/L. Those with lower active B12 showed slower processing speed and delayed visual responses after adjustments for age, sex, education, and cardiovascular risks.
