The Importance of Vitamin B12 in Brain Function
Vitamin B12 plays a crucial role in maintaining brain health, nerve tissue function, and the formation of red blood cells and DNA. Found naturally in protein-rich foods like fish, meat, dairy, and eggs, B12 is also available in fortified cereals and supplements. While a true B12 deficiency is uncommon, low or marginal levels are widespread, affecting up to 40% of people in Western populations.
A recent study has found that both lower and higher levels of vitamin B12 within the normal range may be linked to cognitive issues in older adults. The findings suggest that maintaining an optimal B12 balance could be more complex than previously thought, raising questions about current dietary recommendations.
Lower B12 Levels and Cognitive Decline
Researchers at the University of California, San Francisco, conducted a study on 231 healthy older adults, averaging 71 years of age, who were part of the Brain Aging Network for Cognitive Health. Blood samples were taken to measure total B12 and holo-transcobalamin (holo-TC), also known as ‘active B12,’ which is the form biologically available to cells.
While nearly all participants had B12 levels within the normal range, those with lower B12 levels showed signs of slower brain signal transmission and cognitive processing. Specifically, these individuals exhibited delays in multifocal visual evoked potentials (mfVEP), which indicate reduced conductivity in the brain. Additionally, they had larger volumes of white matter hyperintensities—brain abnormalities linked to cognitive impairment.
Dr. Ari J. Green, the study’s lead author, explained that even when B12 levels were considered adequate by standard measures, the negative effects on cognition were still observed, particularly when analyzing ‘active B12’ levels. The study suggests that routine blood tests measuring total B12 may not provide a full picture of an individual’s neurological health.
The Impact of Higher B12 Levels on Cognitive Function
On the opposite end of the spectrum, the study also found potential risks associated with high B12 levels. Participants with elevated B12 levels showed increased amounts of T-Tau protein, a biomarker linked to neurodegenerative diseases such as Alzheimer’s. This association was most pronounced when high levels of inactive B12 (holo-HC) were present, raising concerns about whether excess B12 could contribute to brain cell damage.
Experts suggest that more research is needed to determine the underlying mechanisms of these findings. Dr. Green noted that current methods for measuring B12 might mislead doctors and patients by not distinguishing between active and inactive forms of the vitamin.
Reevaluating B12 Recommendations
The study’s findings suggest that guidelines for B12 intake may need to be reconsidered, particularly for older adults. Instead of solely relying on blood B12 levels, future recommendations could incorporate measurements of active versus inactive B12 and assess cognitive function as part of routine health evaluations.
To maintain proper B12 levels, experts recommend a diet rich in natural B12 sources such as salmon, beef, and dairy products. Since plant-based foods lack B12, vegetarians and vegans may need to take supplements to avoid deficiencies. While B12 supplements are generally considered safe, the study highlights the importance of ensuring that levels remain balanced to support optimal brain health in aging populations.
