Vitamin B6 and B6 Deficiency

The active coenzyme form of vitamin B6 is called P5P (or sometimes PLP), and is involved in many functions in the body, including protein metabolism, the release of glucose from storage in glycogen, hemoglobin synthesis, fatty acid metabolism, the synthesis of neurotransmitters (in particular serotonin and dopamine), in hormone function and immune function.

Systemic inflammation may impair the function of Vitamin B6.  There are also several kinds of medications, including NSAIDs and oral contraceptives, that interfere with vitamin B6 metabolism.  Pregnancy and nursing increase B6 needs and low B6 can cause severe morning sickness.

"Vitamin B6, also called pyridoxine, is one of 8 B vitamins. All B vitamins help the body convert food (carbohydrates) into fuel (glucose), which is used to produce energy. These B vitamins, often referred to as B complex vitamins, also help the body metabolize fats and protein. B complex vitamins are needed for healthy skin, hair, eyes, and liver. They also help the nervous system function properly.  All B vitamins are water-soluble, meaning that the body does not store them."

"Dietary deficiency, though rare, can develop because extensive processing can deplete foods of vitamin B6.  Secondary deficiency most often results from protein-energy undernutrition,  malabsorption,  alcoholism, use of pyridoxine-inactivating drugs (eg, anticonvulsants, isoniazid, cycloserine, hydralazine, corticosteroids, penicillamine), and Excessive loss. Rarely, secondary deficiency results from increased metabolic demand (eg, in hyperthyroidism)."

"A new study shows a strong association between chronic inflammation and the essential vitamin found in foods such as lean meats, legumes, and vegetables. Researchers found that people with the lowest levels of vitamin B6 in their blood had the highest levels of chronic inflammation, based on a wide variety of indicators. Those with the most vitamin B6 circulating in the bloodstream were also the least likely to have indicators of inflammation."

Signs of B6 deficiency can include:

"Symptoms can include peripheral neuropathy, a pellagra-like syndrome, anemia, and seizures, which, particularly in infants, may not resolve when treated with anticonvulsants. Impaired metabolism (dependency) is rare; it causes various symptoms, including seizures, intellectual disability, and anemia. Diagnosis is usually clinical; no laboratory test readily assesses vitamin B6 status. Treatment consists of giving oral vitamin B6 and, when possible, treating the cause."

"Deficiency causes peripheral neuropathy and a pellagra-like syndrome, with seborrheic dermatitis, glossitis, and cheilosis, and, in adults, can cause depression, confusion, EEG abnormalities, and seizures. Rarely, deficiency or dependency causes seizures in infants. Seizures, particularly in infants, may be refractory to treatment with anticonvulsants. Normocytic, microcytic, or sideroblastic anemia can also develop."

"Other neurologic symptoms observed in severe vitamin B6 deficiency include irritability, depression, and confusion; additional symptoms include inflammation of the tongue, sores or ulcers of the mouth, and ulcers of the skin at the corners of the mouth."

"The American and Canadian Colleges of Obstetrics and Gynecology have recommended the use of vitamin B6 (pyridoxine hydrochloride, 10 mg) and doxylamine succinate (10 mg) as first-line therapy for NVP (nausea and vomiting in pregnancy)."

"One large study found that women who took 500 mg of vitamin B6 daily along with 1,000 mcg of cyanocobalamin (vitamin B12) and 2,500 mcg of folic acid reduced their risk of developing AMD (age-related macular degeneration), an eye disease that can cause loss of vision."

Possible toxicity of B6:

"Although vitamin B6 is a water-soluble vitamin and is excreted in the urine, long-term supplementation with very high doses of pyridoxine may result in painful neurological symptoms known as sensory neuropathy. Symptoms include pain and numbness of the extremities and in severe cases, difficulty walking. Sensory neuropathy typically develops at doses of pyridoxine in excess of 1,000 mg per day. However, there have been a few case reports of individuals who developed sensory neuropathies at doses of less than 500 mg daily over a period of months. Yet, none of the studies in which an objective neurological examination was performed reported evidence of sensory nerve damage at intakes below 200 mg pyridoxine daily. To prevent sensory neuropathy in virtually all individuals, the Food and Nutrition Board of the Institute of Medicine set the tolerable upper intake level (UL) for pyridoxine at 100 mg/day for adults."

Sources:
The Linus Pauling Institute at Oregon State University
http://lpi.oregonstate.edu/infocenter/vitamins/vitaminB6/

University of Maryland Medical Center
http://umm.edu/health/medical/altmed/supplement/vitamin-b6-pyridoxine

The Merck Manual
http://www.merckmanuals.com/professional/nutritional_disorders/vitamin_deficiency_dependency_and_toxicity/vitamin_b6.html

WebMD
http://www.webmd.com/heart/news/20120619/low-vitamin-b6-linked-to-inflammation

More Information:

Intake of vitamins B6 and C and the risk of kidney stones in women.
"Urinary oxalate is an important determinant of calcium oxalate kidney stone formation. High doses of vitamin B6 may decrease oxalate production.. A high intake of vitamin B6 was inversely associated with risk of stone formation."

B6-responsive disorders: a model of vitamin dependency.

"Pyridoxal phosphate is the cofactor for over 100 enzyme-catalysed reactions in the body, including many involved in the synthesis or catabolism of neurotransmitters. Inadequate levels of pyridoxal phosphate in the brain cause neurological dysfunction, particularly epilepsy. There are several different mechanisms that lead to an increased requirement for pyridoxine and/or pyridoxal phosphate. These include: (i) inborn errors affecting the pathways of B(6) vitamer metabolism; (ii) inborn errors that lead to accumulation of small molecules that react with pyridoxal phosphate and inactivate it; (iii) drugs that react with pyridoxal phosphate; (iv) coeliac disease, which is thought to lead to malabsorption of B(6) vitamers; (v) renal dialysis, which leads to increased losses of B(6) vitamers from the circulation; (vi) drugs that affect the metabolism of B(6) vitamers; and (vii) inborn errors affecting specific pyridoxal phosphate-dependent enzymes. The last show a very variable degree of pyridoxine responsiveness, from 90% in X-linked sideroblastic anaemia (delta-aminolevulinate synthase deficiency) through 50% in homocystinuria (cystathionine beta-synthase deficiency) to 5% in ornithinaemia with gyrate atrophy (ornithine delta-aminotransferase deficiency). The possible role of pyridoxal phosphate as a chaperone during folding of nascent enzymes is discussed. High-dose pyridoxine or pyridoxal phosphate may have deleterious side-effects (particularly peripheral neuropathy with pyridoxine) and this must be considered in treatment regimes. None the less, in some patients, particularly infants with intractable epilepsy, treatment with pyridoxine or pyridoxal phosphate can be life-saving, and in other infants with inborn errors of metabolism B(6) treatment can be extremely beneficial."

Vitamin B6 supplementation lowers inflammation in rheumatoid arthritis patients

"The September, 2010 issue of the European Journal of Clinical Nutrition reported a trial conducted by researchers in Taiwan which found an anti-inflammatory benefit for pyridoxine (vitamin B6) supplementation in rheumatoid arthritis patients."