Vitamin B12 "normal" levels may be neither normal nor safe for the aging brain

I've argued for years that the threshold for B12 deficiency is set too low, and new research from the Annals of Neurology makes that case more forcefully than ever. Researchers at UCSF enrolled 231 healthy older adults with B12 levels considered entirely normal by current standards and found that participants with lower levels of the form of B12 your cells can actually absorb and use (called holotranscobalamin) showed slower nerve signaling in the visual pathway, slower cognitive processing that became more pronounced with age, and more areas of white matter damage visible on brain MRI.

Neurological changes were measurable at levels the medical system considers acceptable. The current US deficiency cutoff was not based on clinical outcomes; it was calculated as a statistical threshold using population averages.

In my clinical practice, I saw this pattern repeatedly: patients with cognitive and neurological complaints whose primary care doctors had reassured them their B12 was "normal," but whose homocysteine, holotranscobalamin, and methylmalonic acid levels told a very different story. Those functional markers reveal whether B12 is actually reaching cells and being used, and very few physicians test for them.

In addition, for people who eat a lot meat and animal products, their B12 levels tend to be higher above 2000. There is not issue at all with levels that high. Actually, this new study support the fact that higher B12 levels is important in the elderly.

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Vitamin B12 "normal" levels may be neither normal nor safe for the aging brain