Vitamin B6 (Pyridoxine)

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Vitamin B6 is actually composed of a group of chemicals: pyridoxine, pyridoxal, and pyridoxamine. Pyridoxine is found in plants and the other two are found mainly in animals. Pyridoxal phosphate is the biologically active co-enzyme.

GOOD SOURCES: Potatoes, Legumes, Animal proteins, spinach, broccoli, bananas, wheat germ, corn, egg yolk, liver.

DRI: 1-1.7 mg/d. However, the requirement for pyridoxine goes up when you have a high protein intake.

FUNCTIONS:  Vitamin B6 is needed to metabolize proteins and is important for a healthy immune system, nerves, bones and arteries. Vitamin B6 is a complex of three similar molecules: Pyridoxine, Pyridoxal and Pyridoxamine. All are present in foods and converted into pyridoxal-5-phosphate, the most active coenzyme form. The primary functions of vitamin B6 are in protein metabolism, transferring amino acid and sulfur groups. Roles in synthesis of heme (for hemoglobin), niacin, neurotransmitters, connective tissues, eicosanoids and sphingolipids in nerve sheaths are also essential. Vitamin B6 also participates in the utilization of glycogen and immune function.

Cofactor Functions:

  • Cofactor to 112 known enzymes
  • Cofactor for dopa decarboxylase which converts L-dopa to dopamine and 5HTP to serotonin
  • Cofactor to alanine-glyoxalate aminotransferase which converts glyoxylate to glycine
  • Cofactor to erythrocyte alanine aminotransferase which transfers amino groups
  • Cofactor to aspartate aminotransferase which moves amino groups between aspartate & glutamate
  • Cofactor to glycogen phosphorylase which releases glucose from glycogen
  • Cofactor to ornithine aminotransferase which makes proline & prevents gyrate atrophy (retinal degeneration)
  • Cofactor to glutamic acid decarboxylase that converts glutamate to the neurotransmitter GABA
  • Cofactor in the utilization of selenium (disconnects selenium from selenoproteins for use in the body)
  • Conversion to PLP is vitamin B2 dependent; Deficiency of B2 impacts B6 function
  • Cofactor in the synthesis and function of several neurotransmitters including serotonin, gamma-amino-butyric acid (GABA), dopamine, epinephrine and norepinephrine
  • Cofactor in mitochondrial respiratory chain to produce energy via ATP (adenosine triphosphate)
  • Cofactor to enzymes that converts homocysteine to cysteine (cystathionine synthase and cystathionase)
  • Cofactor in the synthesis of taurine
  • Cofactor in the synthesis of heme (hemoglobin)
  • Cofactor in the metabolism of vitamin B3 (niacin) from tryptophan via kynurenine pathway
  • Cofactor in the synthesis of connective tissue and eicosanoids
  • Cofactor in the synthesis of sphingolipids for nerve cell insulation
  • Cofactor in the synthesis of antibodies (key role in immune function)
  • Cofactor for tyrosine decarboxylase, which catalyzes the conversion of tyrosine to tyramine
  • Cofactor to lysyl oxidase which builds arterial integrity via role in collagen and elastin structure
  • Cofactor to aminolevulinic acid synthase which aids in hemoglobin synthesis
  • Cofactor to serine hydroxymethyltransferase which transfers methyl groups from serine to folate and initiates immune cell proliferation
  • Cofactor to serine palmitoyltransferase which makes sphingolipids for nerve cell insulation
  • Cofactor to serine facemase which synthesized neurotransmitter D-serine
  • Cofactor to sphinosine-1-phosphate lysase which makes sphingolipids for nerve cell insulation
  • Cofactor to cystathionine-b-synthase which metabolizes homocysteine and serine to form cystathionine
  • Cofactor or kynureninanse which metabolizes tryptophan into vitamin B3 for NAD cofactors
  • Cofactor to GABA aminotransferase which breaks down GABA
  • Cofactor to diamine oxidase, which catabolizes exogenous histidine in the gut
  • Cofactor for histidine decarboxylase which converts histidine to histamine

All Other Functions:

  • B6 is a complex of three molecules: pyridozine, pyridoxal, and pyridoxamine which are all converted to pyridoxal-5-phosphate (PLP), the active coenzyme form
  • Bins with histamine and inactivates it (may mitigate allergic response in asthma)
  • Increases peripheral metabolism of levodopa (l-dopa) making it less available for uptake into the brain (may diminish effectiveness of l-dopa medication for Parkinson’s patients when not given with carbidopa which is a peripheral decarboxylase inhibitor)
  • High dose B6 can be as effective as Ritalin for ADHD due to its effect of increasing serotonin
  • Synergistic effect with magnesium for autism patients
  • Increases intracellular uptake of magnesium and vice versa
  • Low B6 linked to high CRP (C-reactive protein), a marker of inflammation
  • Supplementation suppresses pro-inflammatory cytokines such as IL-6 and TNF-a
  • Tissue specific depletion of B6 occurs during inflammation
  • Crucial for DNA methylation thus regulating gene expression
  • Deficiency impairs conversion of alpha-linolenic acid to EPA and DHA
  • Protects genes from estrogen-induced damage (detoxifies estrogen) lowering risk of hormone related cancers
  • Regulates sex hormones and binds to steroid hormone receptors, thus decreasing their effects
  • Reduces prolactin levels which stimulates hypothalamus to increase testosterone
  • Inhibits pituitary (and other tissue) tumor proliferation via role in apoptosis (programmed cell death)

DEFICIENCIES: Convulsion, nausea, flaky skin, HA, insomnia (uncommon). Isoniazid can induce a  deficiency, so you have to supplement with isoniazid prescription. Deficiency is rare but has been seen in infants with low intake of B6, females on OCP’s, and alcoholics.

Early vitamin B6 deficiency symptoms are primarily peripheral neuropathy, weakness, irritability, depression, insomnia and anxiety. More severe deficiency leads to dermatitis, nausea, vomiting and convulsions. Carpal tunnel syndrome,

premenstrual tension syndrome and atherosclerosis may also be related to vitamin B6 deficiency. Sideroblastic anemia is indicative of vitamin B6 deficiency. Homocysteine levels in serum may be elevated by a vitamin B6 deficiency.

TOXICITY: Nerve damage (it is the most toxic water soluble vitamin) @ doses > 200mg. Substantial improvement, but not complete recovery, occurs when the vitamin is removed. Another source indicated neurologic symptoms at doses of 2 grams/d.