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Updated: January 15, History of changes to this fact sheet. Find ODS on:. Strengthening Knowledge and Understanding of Dietary Supplements. Health Information Health Information. Vitamin B6 Fact Sheet for Consumers. Table of Contents What is vitamin B6 and what does it do? How much vitamin B6 do I need? What foods provide vitamin B6?
What kinds of vitamin B6 dietary supplements are available? Am I getting enough vitamin B6? What happens if I don't get enough vitamin B6?
What are some effects of vitamin B6 on health? Can vitamin B6 be harmful? Plasma PLP concentrations are also low in patients receiving maintenance kidney dialysis or intermittent peritoneal dialysis, as well as those who have undergone a kidney transplant, perhaps due to increased metabolic clearance of PLP [ 11 ]. Patients with kidney disease often show clinical symptoms similar to those of people with vitamin B6 deficiency [ 11 ]. People with rheumatoid arthritis often have low vitamin B6 concentrations, and vitamin B6 concentrations tend to decrease with increased disease severity [ 3 ].
These low vitamin B6 levels are due to the inflammation caused by the disease and, in turn, increase the inflammation associated with the disease. Although vitamin B6 supplements can normalize vitamin B6 concentrations in patients with rheumatoid arthritis, they do not suppress the production of inflammatory cytokines or decrease levels of inflammatory markers [ 3 , 12 ].
Patients with celiac disease, Crohn's disease, ulcerative colitis, inflammatory bowel disease, and other malabsorptive autoimmune disorders tend to have low plasma PLP concentrations [ 3 ]. The mechanisms for this effect are not known.
However, celiac disease is associated with lower pyridoxine absorption, and low PLP concentrations in inflammatory bowel disease could be due to the inflammatory response [ 3 ]. Plasma PLP concentrations tend to be very low in people with alcohol dependence [ 1 ].
Alcohol produces acetaldehyde, which decreases net PLP formation by cells and competes with PLP in protein binding [ 1 , 3 ]. As a result, the PLP in cells might be more susceptible to hydrolysis by membrane-bound phosphatase.
People with alcohol dependence might benefit from pyridoxine supplementation [ 3 ]. Scientists have hypothesized that certain B vitamins folic acid, vitamin B12, and vitamin B6 might reduce cardiovascular disease risk by lowering homocysteine levels [ 1 , 13 ]. Therefore, several clinical trials have assessed the safety and efficacy of supplemental doses of B vitamins to reduce heart disease risk. Evaluating the impact of vitamin B6 from many of these trials is challenging because these studies also included folic acid and vitamin B12 supplementation.
Moreover, most other large clinical trials have failed to demonstrate that supplemental B vitamins actually reduce the risk of cardiovascular events, even though they lower homocysteine levels. The combined analysis of data from these two trials showed no benefit of vitamin B6 supplementation, with or without folic acid 0.
In a trial of adults who had suffered a nondisabling stroke, supplementation with high or low doses of a combination of vitamins B6 and B12 and folic acid for 2 years had no effect on subsequent stroke incidence, cardiovascular events, or risk of death [ 16 ]. The research to date provides little evidence that supplemental amounts of vitamin B6, alone or with folic acid and vitamin B12, can help reduce the risk or severity of cardiovascular disease and stroke.
Some research has associated low plasma vitamin B6 concentrations with an increased risk of certain kinds of cancer [ 3 ]. However, the small number of clinical trials completed to date has not shown that vitamin B6 supplementation can help prevent cancer or reduce its impact on mortality.
For example, an analysis of data from two large randomized, double-blind, placebo-controlled trials in Norway found no association between vitamin B6 supplementation and cancer incidence, mortality, or all-cause mortality [ 18 ].
Poor vitamin B6 status has been hypothesized to play a role in the cognitive decline that some older adults experience [ 19 ]. Several studies have demonstrated an association between vitamin B6 and brain function in the elderly. For example, an analysis of data from the Boston Normative Aging Study found associations between higher serum vitamin B6 concentrations and better memory test scores in 70 men aged 54—81 years [ 20 ].
According to this review, most of the studies were of low quality and limited applicability. A Cochrane review found no evidence that short-term vitamin B6 supplementation for 5—12 weeks improves cognitive function or mood in the two studies that the authors evaluated [ 21 ].
The review did find some evidence that daily vitamin B6 supplements 20 mg can affect biochemical indices of vitamin B6 status in healthy older men, but these changes had no overall impact on cognition. More evidence is needed to determine whether vitamin B6 supplements might help prevent or treat cognitive decline in elderly people.
Some evidence suggests that vitamin B6 supplements could reduce the symptoms of premenstrual syndrome PMS , but conclusions are limited due to the poor quality of most studies [ 22 ]. A meta-analysis of nine published trials involving almost 1, women with PMS found that vitamin B6 is more effective in reducing PMS symptoms than placebo, but most of the studies analyzed were small and several had methodological weaknesses [ 22 ].
A more recent double-blind, randomized controlled trial in 94 women found that 80 mg pyridoxine taken daily over the course of three cycles was associated with statistically significant reductions in a broad range of PMS symptoms, including moodiness, irritability, forgetfulness, bloating, and, especially, anxiety [ 23 ]. The potential effectiveness of vitamin B6 in alleviating the mood-related symptoms of PMS could be due to its role as a cofactor in neurotransmitter biosynthesis [ 24 ].
Although vitamin B6 shows promise for alleviating PMS symptoms, more research is needed before drawing firm conclusions. Although this condition is generally known as "morning sickness," it often lasts throughout the day.
The condition is not life threatening and typically goes away after 12—20 weeks, but its symptoms can disrupt a woman's social and physical functioning. Prospective studies on vitamin B6 supplements to treat morning sickness have had mixed results. In two randomized, placebo-controlled trials, 30—75 mg of oral pyridoxine per day significantly decreased nausea in pregnant women who were experiencing nausea [ 27 , 28 ].
The authors of a recent Cochrane review of studies on interventions for nausea and vomiting in pregnancy could not draw firm conclusions on the value of vitamin B6 to control the symptoms of morning sickness [ 26 ]. The American Congress of Obstetrics and Gynecology ACOG recommends monotherapy with 10—25 mg of vitamin B6 three or four times a day to treat nausea and vomiting in pregnancy [ 29 ]. If the patient's condition does not improve, ACOG recommends adding doxylamine. Before taking a vitamin B6 supplement, pregnant women should consult a physician because doses could approach the UL.
High intakes of vitamin B6 from food sources have not been reported to cause adverse effects [ 1 ]. However, chronic administration of 1—6 g oral pyridoxine per day for 12—40 months can cause severe and progressive sensory neuropathy characterized by ataxia loss of control of bodily movements [ 10 , ]. Symptom severity appears to be dose dependent, and the symptoms usually stop if the patient discontinues the pyridoxine supplements as soon as the neurologic symptoms appear.
Other effects of excessive vitamin B6 intakes include painful, disfiguring dermatological lesions; photosensitivity; and gastrointestinal symptoms, such as nausea and heartburn [ 1 , 2 , 30 ]. The scientific literature includes isolated case reports of congenital defects in the infants of women who took pyridoxine supplements during the first half of pregnancy [ 7 ]. However, a more recent observational study found no association between pyridoxine supplementation mean dose ULs are lower for children and adolescents based on body size.
The ULs do not apply to individuals receiving vitamin B6 for medical treatment, but such individuals should be under the care of a physician. This maximum daily dose is based on the maximum safe upper limit for vitamin B6, taken into account that part of vitamin B6 intake comes from food. The maximum safe upper limit for vitamin B6 is lower for children compared to adults.
For this reason, the maximum daily dose of vitamin B6 in dietary supplements for children is also lower:. For full functionality of this site it is necessary to enable JavaScript.
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