New research led by UC San Francisco (UCSF) has found that even mildly low levels of vitamin B12—while still considered within the normal range—can negatively affect brain function in older adults. The study highlights the importance of revisiting current recommendations for vitamin B12 intake, particularly as they may not adequately address the subtle but significant neurological and cognitive effects of lower vitamin B12 levels.
Vitamin B12 plays a vital role in maintaining DNA, red blood cells, and nerve tissue. It is especially important for older adults, as it is involved in maintaining the health of the nervous system and ensuring proper cognitive function. While the standard clinical definition of vitamin B12 deficiency typically refers to severe low levels that cause anemia, this new research suggests that even slightly reduced B12 levels can lead to measurable cognitive impairments, particularly in older adults.
In a study published in Annals of Neurology on February 10, UCSF researchers enrolled 231 healthy adults, average age 71, who did not have dementia or mild cognitive impairment. These participants were recruited from the Brain Aging Network for Cognitive Health (BrANCH) study at UCSF, and their blood B12 levels were measured.
The results showed that participants with lower levels of biologically active vitamin B12—though still above the minimum recommended range—experienced cognitive declines. Specifically, they exhibited slower processing speeds and delays in responding to visual stimuli, indicating impairments in both cognitive and visual processing speeds. MRI scans of these individuals also revealed more white matter lesions in their brains. White matter lesions are often associated with cognitive decline, dementia, and even stroke, further linking low B12 levels to potential brain dysfunction.
The study’s senior author, Dr. Ari J. Green, a neurologist at UCSF, emphasized that the findings challenge the current guidelines for vitamin B12. “Previous studies that defined healthy amounts of B12 may have missed subtle functional manifestations of high or low levels that can affect people without causing overt symptoms,” said Dr. Green.
The research suggests that the current minimum thresholds for B12 may not adequately capture the negative effects of lower B12 levels on brain health. In particular, the study highlighted the role of the biologically active form of B12 in brain function, as this is the form the body can actually utilize. When adjusted for factors such as age, sex, and cardiovascular risk, the researchers found that even small decreases in active B12 were associated with slower cognitive function and greater brain lesions.
Co-first author Alexandra Beaudry-Richard, MSc, who is completing her doctorate in research and medicine at UCSF, noted that the findings may have broader implications for aging populations. “These lower levels could impact cognition to a greater extent than what we previously thought, and may affect a much larger proportion of the population than we realize,” she said. As the population ages, the potential for vitamin B12-related cognitive impairment becomes more concerning.
Dr. Green suggests that the results of the study could prompt healthcare providers to reassess the threshold for B12 deficiency. By incorporating functional biomarkers, such as cognitive tests and brain scans, into B12 assessments, doctors could detect subtle impairments earlier and potentially prevent more significant cognitive decline in the future. “Revisiting the definition of B12 deficiency to incorporate functional biomarkers could lead to earlier intervention and prevention of cognitive decline,” Green said.
This study raises important questions about the adequacy of current vitamin B12 recommendations, particularly for older adults. While vitamin B12 deficiency has long been associated with serious conditions like anemia, this research suggests that even mild insufficiencies can have a lasting impact on brain health. Given the growing number of older adults at risk, these findings call for updated guidelines that better address the functional and neurological impact of vitamin B12 levels.
In conclusion, ensuring that older adults maintain sufficient levels of vitamin B12 could be a crucial factor in preserving cognitive function and preventing brain-related diseases, such as dementia. This research highlights the need for more precise and personalized vitamin B12 assessments to safeguard the brain health of aging populations.
