Study Links Lower Active Vitamin B12 Levels to Slower Cognitive Processing in Older Adults
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A new study from the University of California, San Francisco (UCSF) has found that older adults with lower levels of the biologically active form of vitamin B12 performed more slowly on cognitive speed tests and showed more signs of brain aging on MRI scans. The research involved 231 healthy participants with an average age of 71, none of whom had dementia. While the study identifies an association, it does not prove that low B12 causes cognitive decline.
Facts First
- Lower active B12 linked to slower cognitive speed in healthy older adults after adjusting for age, sex, and other factors.
- MRI scans showed more white matter lesions in participants with lower active B12 levels.
- Study focused on biologically active B12, not total B12, in 231 participants with an average age of 71.
- Participants' average B12 levels exceeded the U.S. minimum, suggesting the findings may apply even to those not clinically deficient.
- A 2025 review concluded B12 deficiency is a modifiable risk factor for neurological problems in older adults and vegetarians.
What Happened
Researchers at the University of California, San Francisco (UCSF) published a study in the journal Annals of Neurology examining the link between vitamin B12 and brain health in older adults. The study involved 231 healthy participants from the Brain Aging Network for Cognitive Health (BrANCH) study, with an average age of 71 and no dementia or mild cognitive impairment. The team, led by senior author Ari J. Green, MD, focused specifically on the biologically active form of vitamin B12. After adjusting for factors like age and cardiovascular risk, they found that participants with lower active B12 levels showed slower processing speed on cognitive tests, including delayed responses to visual stimuli. MRI scans also revealed that these individuals had a higher volume of white matter lesions, which are associated with brain aging.
Why this Matters to You
This research suggests that even if your blood B12 level is above the clinical deficiency cutoff, the amount of active B12 available to your brain may still influence cognitive speed and brain health as you age. For older adults, this could mean that maintaining optimal B12 status might be one factor in preserving mental sharpness. The findings are particularly relevant for vegetarians and older adults, who a separate 2025 review identified as being at higher risk for B12 deficiency-related neurological issues. However, it is important to note that the study shows an association, not a cause, and the cognitive differences observed were specific to processing speed.
What's Next
The UCSF team's findings highlight the potential importance of measuring the active form of B12, not just total levels, in future research on aging and cognition. Further studies are needed to determine if supplementing with B12 can improve cognitive processing speed or reduce white matter lesions in older adults with lower active levels. A 2025 meta-analysis found only a very small benefit from B vitamin supplementation on global cognitive function in older adults, suggesting any potential intervention may have limited effects. Researchers may next investigate whether targeted B12 supplementation for individuals with low active levels could yield more specific benefits.