Vitamin B6 (Pyridoxine)

According to [Ueland2015  🕮 ], "Vitamin B6 is a generic term, which refers to six interconvertible compounds:" "pyridoxine (PN), pyridoxamine (PM), pyridoxal (PL), and their phosphorylated derivatives pyridoxine 5'-phosphate (PNP), pyridoxamine 5'-phosphate (PMP) and pyridoxal 5'-phosphate (PLP)"

PLP is the biologically active form and is often referred to as activated B6.

[Ueland2015  🕮 ] has reviewed both direct and functional vitamin B6 nutritional status markers. The authors stress that vitamin B6 nutritional status is best measured using multiple methods because many confounding factors, including inflammation, renal and liver function, etc., are involved.

The most common direct assay is plasma pyridoxal 5'-phosphate (PLP).

Elevated urine levels of xanthurenic acid or kynurenic acid are functional markers of intracellular vitamin B6 deficiency. They can be measured by the Organic Acid Test. However, these tests can be confounded by inflammation, excess estrogen, excess cortisol, or yeast.

[Ueland2015  🕮 ] ssuggests that the ratio between 3-hydroxykynurenine and xanthurenic acid, as measured in the ZRT Neurotransmitter Profile, is less susceptible to confounding factors.

Dr. Weyrich believes the SpectraCell Comprehensive Micronutrient Test may be a reliable measure of functional vitamin B6 status. However, he is unaware of any supporting clinical evidence.

•       [Ueland2015]   Per Magne Ueland, Arve Ulvik, Luisa Rios-Avila, Øivind Midttun, Jesse F Gregory. Direct and Functional Biomarkers of Vitamin B6 Status. Annu Rev Nutr. 2015:35:33-70. doi: 10.1146/annurev-nutr-071714-034330. PMID: 25974692 DOI: 10.1146/annurev-nutr-071714-034330 PCMID: PMC5988249