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Pyroluria is one potential cause of vitamin B6 deficiency. An overdose of pyridoxine can cause a temporary deadening of certain nerves such as the proprioceptory nerves; causing a feeling of disembodiment common with the loss of Proprioception .

In women, another potential cause for vitamin B-6 deficiency is use of oral contraceptives and other medications containing estro-progestational hormones (such as those prescribed as part of Hormone Replacement Therapy [HRT ). Other contraceptive medications that may cause vitamin B-6 deficiency include: the patch (Ortho Evera), vaginal ring (Nuvaring), hormonal IUD (Mirena) and shot (Depo Provera). Specifically, habitual use of estro-progestational hormones inhibit absorption of vitamin B-6 (due to a disturbance of tryptophan metabolism), necessitating a larger daily doseage of B-6 into the bloodstream. Signs of a Vitamin B-6 deficiency include: depression, anxiety, loss of libido, insomnia, water retention, inability to process glucose (weight loss/gain). Physicians are now beginning to recommend routine vitamin B-6 administation during hormonal contraception/medication.

At least one preliminary study has found that this vitamin may increase to Serotonin .

A Meta-study of three databases ( MEDLINE , EMBASE , and Cochrane Library ), including only Double-blind , randomized controlled trials, found that vitamin B6 has a significant effect compared to Placebo s in treating Morning Sickness , similar to that of Ginger Pregnancy Morning Sickness - Ginger as Effective as Vitamin B6 (open) Effectiveness and Safety of Ginger in the Treatment of Pregnancy-Induced Nausea and Vomiting (subscription) , Borrelli et al., ''Obstetrics & Gynecology'', 2005;105:849-856.

The US RDA varies between 1.3 mg and 2.0 mg, depending upon age and gender.


OCCURRENCE

Vitamin B6 is prevalent in both animal and vegetable food sources. Liver , Chicken , Fish , Green Beans , field Salad , Wheat Germ , Yeast and Bananas are particularly good food sources.


HISTORY

Vitamin B6 is a water-soluble compound that was discovered in 1930s during nutrition studies on rats. The vitamin was named pyridoxine to indicate its structural homology to pyridine. Later it was shown that vitamin B6 could exist in two other, slightly different, chemical forms, termed pyridoxal and pyridoxamine. All three forms of vitamin B6 are precursor of an activated compound known as pyridoxal 5'-phosphate (PLP), which plays a vital role as the cofactor of a large number of essential enzymes in the human body.
Enzymes dependent on PLP catalyze a wide variety of chemical reactions mainly involving amino acids. The reactions carried out by the PLP-dependent enzymes that act on amino acids include transfer of the amino group, decarboxylation, racemization, and beta- or gamma-elimination or replacement. Such versatility arises from the ability of PLP to covalently bind the substrate, and then to act as an electrophilic catalyst, thereby stabilizing different types of carbanionic reaction intermediates.
Overall, the Enzyme Commission (EC; http://www.chem.qmul.ac.uk/iubmb/enzyme/) has catalogued more than 140 PLP-dependent activities, corresponding to ~4% of all classified activities.


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