Key Points:
- Low B12 levels within the normal range are associated with slower brain electrical conductivity based on EEG readings.
- Low B12 levels within the normal range are associated with slower cognitive performance.
- MRI scans show evidence of brain damage associated with low B12 levels inside the normal range.
A total of 231 healthy older adults with “normal” blood B12 levels were enrolled in a new study published in the Annals of Neurology. In the study, researchers from the University of California San Francisco (UCSF) found that normal B12 levels were associated with neurological deficits such as impaired processing speed. These findings call for the current vitamin B12 deficiency threshold, which is not based on medical research, to be updated. In fact, the threshold may need to be tripled, increasing from 148 pmol/L to 410 pmol/L.
B12 Levels Associated with Slower Brain Function
To assess brain function, the USCF researchers showed participants flashes of light and measured the responding electrical changes occurring in the brain’s visual cortex using an electroencephalogram (EEG). Alarmingly, the results showed that slower brain conductivity was associated with B12 levels within the supposed normal range, suggesting that inadequate B12 levels are associated with impaired brain function.
After vitamin B12 is absorbed through the intestinal wall, it attaches to proteins that transport it through our bloodstream. There are two proteins that B12 attaches to, which determine how easily it is utilized by our body. If it attaches to a protein called transcobalamin, it easily goes into all cells. Therefore, transcobalamin-attached B12 is considered the biologically available active form of vitamin B12. In contrast, when B12 attaches to a protein called haptocorrin, it is only able to enter liver cells and is considered the inactive form of B12. The researchers found that slower brain conductivity was associated with the active form of vitamin B12 but not the inactive form.
“This analysis supports our hypothesis that the lack of available B12 induces a delay in conduction speed through the brain,” said the authors.
B12 Levels Associated with Slower Thinking
To assess cognitive performance, the researchers had the participants complete a battery of five visual tasks to test their reaction time. This involved tasks such as matching abstract shapes and mentally rotating letters from the Georgian Cyrillic alphabet. The tests showed that the cognitive processing speed of the participants varied, and this variation was associated with B12 levels. Participants with lower processing speed (faster performance) had higher B12 levels and vice versa. Moreover, only the active form of vitamin B12 was associated with impaired processing speed. The impairment was also age-dependent, with low-B12 participants over 75 years old showing the slowest response times.
B12 Levels Associated with Brain Damage and Degeneration
Our brain is thoroughly connected by the axons of neurons, which are covered in fat that appears white. This white matter can be visualized with MRI (magnetic resonance imaging), where it also appears white. Brighter spots of white are called hyperintensities, an indicator of structural damage. White matter hyperintensities predict the increased risk of stroke, dementia, and death. Because white matter hyperintensities are also associated with B12 deficiency, the UCSF researchers measured them from participants. The results showed that low active B12 levels were associated with more white matter hyperintensities, suggesting that low B12 levels within the normal range could be contributing to brain damage.
The researchers also measured blood protein markers for neurodegeneration called Tau and UCHL-1 (ubiquitin C-terminal hydrolase L1). Increased blood Tau protein is associated with Alzheimer’s disease, the most common form of dementia. Similarly, UCHL-1 is associated with neurodegenerative diseases, particularly Alzheimer’s and Parkinson’s disease. The researchers showed that elevated levels of both these neurodegenerative proteins were associated with higher levels of biologically inactive B12, demonstrating a link between neurodegenerative markers and vitamin B12 availbility.
Correlation not Causation
It is important to realize that this is an observational study based on correlations and does not infer causation. More studies will be needed to determine if low B12 plays a causative role in faster brain aging. Still, the authors say,
“A study on an aging population previously argued for a broadening of the reference range for B12 levels in elder people, and our results further support such a shift to account for age. The elderly population may be particularly vulnerable to the effects of declining B12 availability and may benefit from a change in guidelines for what is currently defined as healthy levels of vitamin B12.”
With that being said, considering the dire consequences of low B12 levels within the normal range, it may not be wise to wait for scientific studies to emerge before taking action. Animal-based foods such as beef, chicken, pork, eggs, milk, cheese, yogurt, and fish are rich in vitamin B12. These foods are also rich in protein, which many older adults do not get enough of. However, those on a vegan diet may need to supplement with vitamin B12.
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