VITAMIN B-6 (Pyridoxine)

General - water-soluble; anti-dermatitis factor;

• Natural B-6 contains 3 equally effective forms: pyridoxine, pyridoxal & pyridoxamine;
• Liver converts vitamin B-6 to metabolically active pyridoxal phosphate;
• Adult body contains about 25 mg of B-6;
• History: suspected in 1926, confirmed in 1935; isolated in 1938; structure identified in 1939;
• other forms identified in 1945; deficiency in infants due to over-processed formulas identified in 1951; requirement in humans established in 1957;

Nutrition

• Sources: best: brewer’s yeast, liver, chicken; good: ham, fish, nuts, whole grains, cauliflower, beans, bananas, raisins; poor: most vegetables & fruits, refined & processed, starchy foods;
• Supplements: B-6, B-complex, multi-vitamin & multi-mineral-vitamin formulations;
• Absorption occurs in the small intestine; 70% absorbed;
• Improved by: other B-complex vitamins & antioxidant vitamin C;
• Stability: relatively stable to heat; destroyed by light, UV, oxidation, alkaline conditions; freezing loses 15-70%; cooking loses up to 40%; milling grains loses 50-90%;
• Storage: throughout the body; slightly elevated concentrations in liver, nerve tissue, muscles & lymphatic system; bound to proteins (albumin & haemoglobin) in blood; body retains small amounts of pyridoxine; adequate daily consumption needed to maintain healthy levels;
• Excretion: through urine;
• Metabolism: converted to active form, pyridoxal-5-phosphate (PLP) in liver & blood cells, catalyzed by magnesium & zinc; circulates in blood attached to albumin protein; requirement increased with high protein & high fat diets;
• Interactions: oral contraceptives, estrogens, anti-depressants interfere with B-6 activity & increase need;
• High doses of B-6 may interfere with levodopa treatment of Parkinson’s disease;

Functions of B-6

• Required for normal growth; necessary for functions of more than 60 enzymes;
• Helps in B-12 absorption;
• Necessary for immune function & cancer protection; improves immune function in elderly;
• Role in heart & artery health; converts toxic, atherogenic homocysteine into methionine;
• Main function of B-6 is transamination & deamination reactions (move amine {NH2} groups between molecules; B-6 links amino acid {protein} & energy metabolism); also involved in decarboxylation reactions;
• PLP is a co-enzyme in the metabolism of carbohydrates, proteins & fats;
• Co-factor in the physiology of muscle, lymph & nerve tissues;
• Regulates energy production in cells; necessary for glucose tolerance; involved in breakdown of glycogen for energy;
• Converts essential fatty acids into prostaglandins (linoleic acid to arachidonic acid);
• Regulates water retention/excretion; maintains proper sodium/potassium ratios;
• Co-enzyme in synthesis of lipids from fatty acids & proteins from amino acids;
• Necessary for formation of vitamin B-3 from tryptophan;
• Improves oral health by maintaining integrity of teeth & facial bones;
• Vital for forming red blood cell pigment (heme), nucleic acids, bile salts, hormones, brain chemicals & immune antibodies;
• Necessary to produce neurotransmitters (epinephrine, serotonin, histamine) from amino acids; low B-6 during brain development results in permanent impairment;
• Plays part in thyroid hormone metabolism & in insulin & growth hormone synthesis;
• Plays part in DNA, RNA & elastin (connective tissue) synthesis;
• Synergized by: B-2, B-3 & biotin, that help convert B-6 into its active form;
• Antagonized by: increased intake of lipids or proteins; stress; pregnancy; aging; more than 40 drugs, including some antibiotics (cycloserine), oral contraceptives (estrogens), tuberculosis drug isoniazid, penicillamine, blood pressure lowering drugs (hydrallazine), anti-metabolites (desoxypyri-doxine) & others;

• Measurement: in milligrams;
• Optimum: (SONA) averages range from 2 to 25 mg/day;
• Individual optimum must be determined by each individual; determined by body weight & diet; 2 mg/100 grams of protein is necessary for positive nitrogen balance & amino acid metabolism; to prevent imbalance, B-6 should be at least equal to B-1 & B-2 consumption;
• Minimum: (DRI) set at 1.3/1.5 mg/day; (2 mg for pregnancy)
• Less than RDA: 80% of population, according to a U.S. government survey; almost 50% of population obtains less than 70% of RDA;
• Deficiency from inadequate diet, oestrogen birth control pills, pharmaceutical drugs; pregnancy & lactation; chronic alcohol use; high protein diet; poor absorption; higher requirement; unsupplemented fasting & reducing diets; increased need during pregnancy, lactation, exposure to radiation, cardiac failure, ageing;
• Symptoms include: headache; dizziness; generalized weakness & fatigue; irritability; unable to concentrate; insomnia; depression; water retention; skin lesions: sores on lips, skin & tongue; white blood cell dysfunctions; dandruff & oily scales on scalp & eye-brows (seborrhoeic dermatitis); iron-resistant anaemia; disorders of nerves, heart & joints; poor wound healing; abdominal distress, vomiting; poor growth; erratic blood glucose levels; abnormal decrease in haemoglobin level (hypo chromic anaemia); inability to convert tryptophan into vitamin B-3; kidney stones; brain wave (EEG) abnormalities; nerve degeneration; low blood sugar, glucose intolerance, insensitivity to insulin; numbness & cramps in arms & legs; visual disturbances, neuritis, arthritis, limb paralysis, heart disorders involving nerves; increased urination;
• Infants: convulsive seizures of cerebral origin;
• Prenatal deficiency: may result in blood disorders & mental retardation of infants;
• Severe deficiency may result in stillbirth;
• Toxicity: low; 50 times RDA is safe over long term; at levels approaching 500 mg/day, may develop sensory neuropathy after several years; 2 to 10 grams/day develop sensory neuropathy within a few months;
• Reversed by cessation of supplement;

Therapy with pyridoxine

• Usual therapeutic dose from 2 to 200 mg/day;
• Useful in treatment of homocysteine-related heart & artery disease;
• Improves immune function in immune deficiency (cancer, AIDS);
• Prevent oxalate kidney stones; mild diuretic;
• Treat depression due to inability to convert tryptophan to neurotransmitter serotonin;
• Helpful in treating allergies, arthritis, asthma, carpal tunnel syndrome;
• Reverses deficiency conditions, certain kinds of anaemia, abnormalities of amino acid metabolism;
• 40 mg/day used to treat morning sickness (nausea & vomiting) during early pregnancy; vital during pregnancy & lactation; may relieve depression from oral contraceptives;
• Improves fertility in some cases of unexplained infertility;
• 50 - 200 mg/day may relieve premenstrual syndrome (PMS);
• Arthritic conditions may be alleviated by high doses of B-6 + cider vinegar & lecithin;
• May improve glucose tolerance in some cases of diabetes mellitus or gestational diabetes;
• May lessen frequency & severity of asthma attacks (wheezing, coughing, breathing difficulties);
• 25 - 200 mg/day may have beneficial effects in treatment of radiation sickness;
• 500 mg/day used to treat carpal tunnel syndrome, instead of penicillamine;
• 250 to 1,000 mg of pyridoxine increase dream recall without disturbing sleep patterns;
• “Mauve factor” (kryptopyrrole) schizophrenics may require 250 - 3,000 mg/day of B-6 to function normally; kryptopyrrole binds B-6, producing deficiency;
• B-6 + magnesium oxide prevent the recurrence of kidney stones;
• Large doses of B-6 + magnesium help treat childhood “autism”.