What is B-Vitamin and Cofactor Status Markers — Functional Deficiency Indicators?
Urinary organic acid metabolites serve as functional downstream indicators of cofactor adequacy — rising when B-vitamin-dependent enzymatic reactions are impaired. Methylmalonic acid (MMA) rises when adenosylcobalamin (B12 mitochondrial cofactor) is insufficient, impairing methylmalonyl-CoA mutase — providing earlier evidence of functional B12 deficiency than serum B12 alone. Xanthurenate and kynurenate — tryptophan catabolism byproducts — accumulate when pyridoxal-5-phosphate (active B6) is insufficient for kynureninase activity, providing a functional marker of B6 status. Pantothenate deficiency impairs CoA synthesis, affecting multiple acetylation reactions. These metabolic downstream markers provide functional evidence of cofactor inadequacy at the cellular level — often preceding detectable changes in serum vitamin concentrations.