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Commonly searched drugs. Test your knowledge. Chromium is a mineral required in small quantities by the body, and it enables insulin to function. People with which of the following disorders should avoid taking chromium? More Content. Many foods contain vitamin B6, but extensive processing can remove the vitamin. History and physical examination. Blood tests may be done, but no routine blood test can clearly confirm the diagnosis. Correction of the cause. Generic Name Select Brand Names penicillamine.
Was This Page Helpful? Yes No. Vitamin B6 Excess. The authors concluded an unclear role of vitamin B6 in cancer prevention because of the discrepancy between results from epidemiological and intervention studies. They suggested that higher levels of B6 in the body may reflect the status of other nutrients that are protective against cancer.
Vitamin B6 is believed to play a role in colorectal cancer through its enzyme activity that may reduce oxidative stress and the spread of tumor cells. Vitamin B6 deficiency is associated with chronic inflammation, a risk factor for colorectal cancer.
Vitamin B6 has long been documented as a remedy to help relieve pregnancy-related nausea and its most severe form, hyperemesis gravidarum, which sometimes necessitates hospitalization due to severe dehydration. A vitamin B6 deficiency most often occurs when other B vitamins in the body are low, particularly vitamin B12 and folic acid. A mild deficiency may have no symptoms, but a more severe or prolonged deficiency can exhibit the following:.
Certain conditions can increase the risk of developing a deficiency by interfering with the absorption of vitamin B It is quite unlikely to reach a toxic level of vitamin B6 from food sources alone.
Vitamin B6 is a water-soluble vitamin so that unused amounts will exit the body through the urine. Symptoms include:. B Vitamins Vitamins and Minerals. The contents of this website are for educational purposes and are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
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Search for:. Cardiovascular disease High homocysteine levels are associated with an increased risk of heart disease and stroke as it may promote the formation of blood clots and excess free radical cells, and may impair normal blood vessel function.
The participants were given either a B-vitamin complex with folic acid, B12, and B6; folic acid and B12; 40 mg B6 alone; or a placebo. There were no differences in cardiac events or cardiac deaths in the vitamin B6 groups compared with the placebo group. Deficiencies in one or all of these B vitamins may affect both remethylation and transsulfuration processes and result in abnormally elevated homocysteine levels.
An early study found that vitamin B 6 supplementation could lower blood homocysteine levels after an oral dose of methionine was given i. The authors reported an increased rate of cystathionine synthesis with vitamin B 6 restriction, suggesting that homocysteine catabolism in the transsulfuration may be maintained or enhanced in response to a marginal reduction in PLP availability.
Yet, the flux ratio between methionine cycle and transsulfuration pathway appeared to favor homocysteine clearance by remethylation rather than transsulfuration in six out of nine participants Numerous randomized controlled trials , many in subjects with existing hyperhomocysteinemia and vascular dysfunction, have demonstrated that supplementation with folic acid, alone or combined with vitamin B 6 and vitamin B 12 , could effectively reduce fasting plasma homocysteine concentrations.
In 19 intervention studies recently included in a meta-analysis , reductions in homocysteine level in the blood following B-vitamin supplementation ranged between 7.
In contrast, studies supplementing individuals with only vitamin B 6 have usually failed to show an effect on fasting levels of homocysteine 29, Of the three supplemental B vitamins, folic acid appears to be the main determinant in the regulation of fasting homocysteine levels when there is no coexisting deficiency of vitamin B 12 or vitamin B 6 Yet, the effect of homocysteine lowering on CVD risk reduction is debated.
However, most systematic reviews and meta-analyses of B-vitamin intervention studies to date have indicated a lack of causality between the decrease of fasting homocysteine levels and the prevention of cardiovascular events 28 , Moreover, B-vitamin supplementation trials in high-risk subjects have not resulted in significant changes in carotid intima-media thickness CIMT and flow-mediated dilation FMD of the brachial artery, two markers of vascular health used to assess atherosclerotic progression It has been suggested that antiplatelet therapy used in the primary prevention of CVD might interfere with the effect of homocysteine lowering by B vitamins on CVD risk In this context, a post-hoc subgroup analysis of the multicenter, randomized, double blind, placebo-controlled VITATOPS trial 39 proposed that the small benefit of homocysteine-lowering by B vitamins might be cancelled in patients treated with antiplatelet drugs Yet, the benefit of B-vitamin supplementation in primary prevention i.
A growing body of evidence currently suggests that low vitamin B 6 status may increase the risk of cardiovascular disease through mechanisms independent of homocysteine lowering In fact, inflammation is involved in the early steps of atherosclerosis in which lipids deposit in plaques known as atheromas within arterial walls and increase the risk of CAD In a case-control study that included patients with CAD and healthy controls, plasma PLP concentrations were inversely correlated with the levels of two markers of systemic inflammation, C-reactive protein CRP and fibrinogen Moreover, the inverse correlation between PLP levels and inflammatory scores remained significant regardless of vitamin B 6 intakes, questioning again the nature of this relationship.
Finally, while inflammation may contribute to lower vitamin B 6 status, current evidence fails to support a role for vitamin B 6 in the control of inflammation in patients with cardiovascular disease 48, A few observational studies have linked cognitive decline and Alzheimer's disease AD in the elderly with inadequate status of folate , vitamin B 12 , and vitamin B 6 Yet, the relationship between B vitamins and cognitive health in aging is complicated by both the high prevalence of hyperhomocysteinemia and signs of systemic inflammation in elderly people On the one hand, since inflammation may impair vitamin B 6 metabolism, low serum PLP levels may well be caused by processes related to aging rather than by malnutrition.
On the other hand, high serum homocysteine may possibly be a risk factor for cognitive decline in the elderly, although the matter remains under debate. Specifically, the meta-analysis of 19 randomized , placebo -controlled trials of B-vitamin supplementation failed to report any difference in several measures of cognitive function between treatment and placebo groups, despite the treatment effectively lowering homocysteine levels In a recent randomized, double-blind , placebo-controlled study of 2, stroke survivors with or without cognitive impairments, daily supplementation with 2 mg of folic acid, 0.
Yet, the B-vitamin intervention had no effect on either the incidence of newly diagnosed cognitive impairments or on measures of cognitive performance when compared to placebo In contrast, another recent placebo-controlled trial found that a daily B-vitamin regimen that led to significant homocysteine lowering in high-risk elderly individuals could limit the progressive atrophy of gray matter brain regions associated with the AD process Yet, the authors attributed the changes in homocysteine levels primarily to vitamin B Because of mixed findings, it is presently unclear whether supplementation with B vitamins might blunt cognitive decline in the elderly.
Late-life depression is a common disorder sometimes occurring after acute illnesses, such as hip fracture or stroke 55, In a prospective study of 3, free-living people aged 65 and older from the Chicago Health and Aging Project, total vitamin B 6 intakes but not dietary intakes alone were inversely correlated with the incidence of depressive symptoms during a mean follow-up period of 7.
In a randomized , double-blind , placebo -controlled trial in individuals who suffered from a recent stroke, daily supplementation of 2 mg of folic acid, 0. Additional evidence is needed to evaluate whether B vitamins could be included in the routine management of older people at high risk for depression. Chronic inflammation that underlies most cancers may enhance vitamin B 6 degradation see Vitamin B 6 and inflammation. In addition, because PLP is required for the methionine cycle, homocysteine catabolism , and thymidylate synthesis , low vitamin B 6 status might affect these pathways and potentially increase the risk for chronic conditions.
The systematic review of nine prospective studies found either inverse or positive associations between vitamin B 6 intakes and colorectal cancer CRC risk Inconsistent evidence regarding the link between vitamin B 6 intakes and breast cancer was also recently reported in a meta-analysis Yet, a prospective study that followed nearly , older adults for nine years observed that the risk of esophageal and stomach cancers was lower in participants in the highest versus lowest quintile of total vitamin B 6 intakes median values, 2.
Very few randomized , placebo -controlled trials investigating the nature of the association between B vitamins and cancer risk have focused on vitamin B 6. A recent randomized, double-blind , placebo-controlled study conducted in 1, women with high cardiovascular risk showed that daily supplementation with 2. A large prospective study examined the relationship between vitamin B 6 intake and the occurrence of symptomatic kidney stones in women. A group of more than 85, women without a prior history of kidney stones were followed over 14 years, and those who consumed 40 mg or more of vitamin B 6 daily had only two-thirds the risk of developing kidney stones compared with those who consumed 3 mg or less However, in a group of more than 45, men followed for 14 years, no association was found between vitamin B 6 intake and the occurrence of kidney stones Limited experimental data have suggested that supplementation with high doses of pyridoxamine may help decrease the formation of calcium oxalate kidney stones and reduce urinary oxalate levels, an important determinant of calcium oxalate kidney stone formation 68, Presently, the relationship between vitamin B 6 intake and the risk of developing kidney stones requires further study before any recommendations can be made.
Vitamin B 6 supplements at pharmacologic doses i. A few rare inborn metabolic disorders, including pyridoxine-dependent epilepsy PDE and pyridoxamine 5'-phosphate oxidase PNPO deficiency, are the cause of early-onset epileptic encephalopathies that are found to be responsive to pharmacologic doses of vitamin B 6.
Vitamin B 6 has been used since the s to treat nausea during pregnancy. Vitamin B 6 was originally included in the medication Bendectin, which was prescribed for NVP treatment and later withdrawn from the market due to unproven concerns that it increased the risk for birth defects. Vitamin B 6 itself is considered safe during pregnancy and has been used in pregnant women without any evidence of fetal harm The results of two double-blind , placebo -controlled trials, including pregnant women that used 25 mg of pyridoxine every eight hours for three days 75 or 10 mg of pyridoxine every eight hours for five days 76 , suggested that vitamin B 6 may be beneficial in reducing nausea.
A recent systematic review of randomized controlled trials on NVP symptoms during early pregnancy found supplemental vitamin B 6 to be somewhat effective It should be noted that NVP usually resolves without any treatment, making it difficult to perform well-controlled trials.
Supplementation with pyridoxine and the drug doxylamine significantly improved NVP symptoms, as assessed by lower PUQE scores compared to placebo. Moreover, more women supplemented with pyridoxine-doxylamine The American and Canadian Colleges of Obstetrics and Gynecology have recommended the use of vitamin B 6 pyridoxine hydrochloride, 10 mg and doxylamine succinate 10 mg as first-line therapy for NVP Another more recent review of 13 randomized controlled studies also emphasized the need for conclusive evidence before recommendations can be made The importance of PLP-dependent enzymes in the synthesis of several neurotransmitters see Nervous system function has led researchers to consider whether vitamin B 6 deficiency may contribute to the onset of depressive symptoms see Disease Prevention.
There is limited evidence suggesting that supplemental vitamin B 6 may have therapeutic efficacy in the management of depression. Yet, the etiology of late-onset depression is unclear and evidence is currently lacking to suggest whether supplemental B vitamins including vitamin B 6 could relieve depressive symptoms.
Carpal tunnel syndrome CTS causes numbness, pain, and weakness of the hand and fingers due to compression of the median nerve at the wrist. It may result from repetitive stress injury of the wrist or from soft-tissue swelling, which sometimes occurs with pregnancy or hypothyroidism. In addition, a cross-sectional study in men not taking vitamin supplements found that decreased blood levels of PLP were associated with increased pain, tingling, and nocturnal awakening—all symptoms of CTS However, studies using electrophysiological measurements of median nerve conduction have largely failed to find an association between vitamin B 6 deficiency and CTS While a few studies have noted some symptomatic relief with vitamin B 6 supplementation, double-blind , placebo -controlled trials have not generally found vitamin B 6 to be effective in treating CTS Yet, despite its equivocal effectiveness, vitamin B 6 supplementation is sometimes used in complementary therapy in an attempt to avoid hand surgery.
Patients taking high doses of vitamin B 6 should be advised by a physician and monitored for vitamin B 6 -related toxicity symptoms see Toxicity Many plant foods contain a unique form of vitamin B 6 called pyridoxine glucoside; this form of vitamin B 6 appears to be only about half as bioavailable as vitamin B 6 from other food sources or supplements 7.
In most cases, including foods in the diet that are rich in vitamin B 6 should supply enough to meet the current RDA. However, those who follow a very restricted vegetarian diet might need to increase their vitamin B 6 intake by eating foods fortified with vitamin B 6 or by taking a supplement.
Some foods that are relatively rich in vitamin B 6 and their vitamin B 6 content in milligrams mg are listed in Table 2. Vitamin B 6 is available as pyridoxine hydrochloride in multivitamin, vitamin B-complex, and vitamin B 6 supplements Because adverse effects have only been documented from vitamin B 6 supplements and never from food sources, safety concerning only the supplemental form of vitamin B 6 pyridoxine is discussed.
Although vitamin B 6 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, mg per day.
However, there have been a few case reports of individuals who developed sensory neuropathies at doses of less than 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 mg pyridoxine daily Certain medications interfere with the metabolism of vitamin B 6 ; therefore, some individuals may be vulnerable to a vitamin B 6 deficiency if supplemental vitamin B 6 is not taken.
In the NHANES analysis, significantly more current and past users of oral contraceptives OCs among menstruating women had low plasma PLP levels compared to women who have never used OCs, suggesting that the estrogen content of OCs may interfere with vitamin B 6 metabolism see Side effects of oral contraceptives Anti- tuberculosis medications e. PLP bioavailability may also be reduced by methylxanthines, such as theophylline used to treat certain respiratory conditions 7. Conversely, high doses of vitamin B 6 have been found to decrease the efficacy of two anticonvulsants , phenobarbital and phenytoin, and of L-Dopa 6 , Because vitamin B 6 is required for the metabolism of the amino acid tryptophan, the tryptophan load test an assay of tryptophan metabolites after an oral dose of tryptophan has been used as a functional assessment of vitamin B 6 status.
However, most other indices of vitamin B 6 status were normal in women on high-dose OCs, and the estrogen content of OCs appeared to be more likely responsible for the abnormality in tryptophan metabolism Yet, more recently, the use of lower dose formulations has also been associated with vitamin B 6 inadequacy 88 , Although it is not known whether OCs actually impair vitamin B 6 metabolism or merely affect the tissue distribution of PLP, the use of OCs may place women at higher risk of vitamin B 6 deficiency when they discontinue OCs and become pregnant Whether OC users are at higher risk of cardiovascular disease despite normal homocysteine levels also needs to be determined.
Finally, although high doses of vitamin B 6 pyridoxine have demonstrated no benefit in preventing the risk of side effects from OCs 94 , the use of vitamin B 6 supplements may be warranted in current and past OC users. Early metabolic studies have indicated that the requirement for vitamin B 6 in older adults is approximately 2 mg daily Originally written in by: Jane Higdon, Ph. Updated in February by: Jane Higdon, Ph.
Updated in November by: Victoria J. Drake, Ph. Updated in May by: Barbara Delage, Ph. Reviewed in June by: Jesse F. Gregory, Ph. Dakshinamurti S, Dakshinamurti K. Vitamin B 6. Handbook of Vitamins. Effects of vitamin B6 metabolism on oncogenesis, tumor progression and therapeutic responses.
McCormick DB. Present Knowledge in Nutrition. Washington, D. In: Erdman JW Jr. Present Knowldege in Nutrition. Pyridoxal phosphate enzymes: mechanistic, structural, and evolutionary considerations.
Annu Rev Biochem. Leklem JE.
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