This video was informative for me. “Dr Heim talks about a critical cofactor in methylation reactions and mitochondrial bioenergetics, with broad clinical relevance in neurocognitive health, metabolism, muscle function and healthy aging. The importance of understanding the major differences between 4 major forms of this, and how to select the right form and dosing protocol to meet individual needs.”
When it comes to peak performance it looks like the active form of vitamin B12 adenosylcobalamin is a candidate. If performance is a priority for the aging athlete, then being deficient in adenosylcobalami, could be detrimental.
A new UCSF study suggests our clinical definitions of “normal” B12 may be missing the mark—especially when it comes to brain health.
Researchers tracked 231 cognitively normal older adults (median age: 71). Just two had B12 levels below the standard deficiency cutoff of 148 pmol/L—yet both had normal functional markers and remained in the study. The group’s median B12 was 414.8 pmol/L—within the normal range.
But even within that range, lower active B12 (holo-transcobalamin) was linked to slower cognitive processing, delayed visual evoked potentials (a proxy for myelin integrity), and more white matter hyperintensities on MRI.
Meanwhile, higher inactive B12 (holo-haptocorrin) correlated with elevated serum Tau—a biomarker of neurodegeneration.
By the way,
Japan’s reference range for serum B12: 500–1,300 pg/mL (≈ 369–958 pmol/L) U.S. reference range for serum B12: 200–900 pg/mL (≈ 148–664 pmol/L)
It’s not that complicated. Just measure your blood levels of vitamin B12 - a simple easily available test. Supplement if not in good range. If supplements don’t move the needle, then you can investigate further.
Japan’s reference range for serum B12: 500–1,300 pg/mL (≈ 369–958 pmol/L)