A new study published in the Annals of Neurology by researchers at UCSF challenges our current understanding of what constitutes “normal” vitamin B12 levels, particularly regarding brain health. The findings suggest that even B12 levels currently considered adequate may not be optimal for maintaining brain function, especially in older adults.
Key Findings
The study examined 231 healthy older adults with B12 levels that would typically be considered normal. Surprisingly, those with lower B12 levels – though still within the “normal” range – showed several concerning signs:
Slower nerve conduction in visual pathways
Reduced cognitive processing speed, particularly in older participants
More white matter damage visible on brain MRI scans1
Why This Matters
The current normal levels for vitamin B12 were determined decades ago, and it is not clear how reliable the research that led to these values was. Quest and Labcorp, two major chains of laboratories, define normal levels as 200 – 1,000 pg/ml and 232 -1,245 pg/ml, respectively. The WHO considers 480 pg/ml to be the bottom of the normal range, while it is 500 pg/ml in Japan. Some experts suggest these higher standards may contribute to lower rates of Alzheimer’s and dementia in Japan.
What This Means for You
Your B12 levels might be worth checking if you are experiencing neurological symptoms like:
Mental fogginess
Memory issues
Balance problems
Numbness or tingling
Migraine headaches, especially with visual auras
Dizziness
If you have this blood test done, don’t accept “it’s normal” from your doctor, but ask about your actual level.
Why are so many people deficient
Ironically, a healthy diet is low in vitamin B12. Vegetarians are at a greater risk of becoming deficient. Another common factor is antacid medications such as omeprazole (Prilosec), pantoprazole (Protonix), esomeprazole (Nexium), and others. Genetic factors also play a role.
Special Considerations for Older Adults
The study found that older adults may be particularly vulnerable to the effects of lower B12 levels. This is especially important because:
B12 absorption tends to decrease with age
The impact of lower B12 on cognitive processing speed was more pronounced in older participants.
