Benefits
Mood and self-rated anxiety
B6 is needed to make neurotransmitters. In a one-month placebo-controlled trial in young adults, 100 mg a day of B6 lowered self-rated anxiety, with only a trend for depression scores. This was a single trial. That dose equals the US upper limit and is far above the European limit of 12 mg a day, so it is not meant for long-term use without advice.
Memory in older adults
In a 3-month placebo-controlled trial in 76 healthy men aged 70 to 79, 20 mg a day of B6 improved memory scores, mainly long-term memory, with no change in mood. This was a single trial, and a review of 14 randomized trials found insufficient evidence that B6, alone or with other B vitamins, improves cognition in people with normal cognitive function.
Red blood cell formation
PLP is involved in forming hemoglobin, the oxygen-carrying protein in red blood cells, and B6 deficiency is associated with microcytic anemia, a type with small red blood cells. Adequate B6 intake supports normal red blood cell formation.
Normal immune function
In a controlled diet study in 8 healthy older adults, a low-B6 diet reduced lymphocyte numbers and interleukin 2 production, and these returned to baseline once B6 intake was restored to about 1.9 to 2.9 mg a day. This shows B6 is needed for normal immune function; it does not show that extra B6 boosts immunity in people who already get enough.
Homocysteine metabolism
B6 helps keep homocysteine at normal levels. In the HOPE-2 trial of 5,522 adults with vascular disease or diabetes, B6 combined with folic acid and B12 lowered homocysteine, but over five years it did not reduce the combined rate of cardiovascular death, heart attack and stroke compared with placebo.
Morning sickness comfort in pregnancy
In a placebo-controlled trial, 25 mg of B6 every 8 hours for 3 days reduced nausea in women with severe nausea, though not in those with mild to moderate nausea, and fewer had vomiting. Results across trials have varied and a Cochrane review drew no firm conclusions, but a later review of 18 studies with a meta-analysis found better nausea scores. Use it in pregnancy only with your clinician's advice.
Premenstrual symptom support
A systematic review of nine trials in 940 women found that B6, up to 100 mg a day, improved overall premenstrual symptoms more than placebo, and a later trial of 94 women taking 80 mg a day for three cycles also reported fewer symptoms. Most trials were small and of low quality, so the size of the benefit is uncertain.
Protein, carbohydrate and fat metabolism
As PLP, B6 takes part in more than 100 enzyme reactions, mostly in protein metabolism, and also in carbohydrate and fat metabolism, including making glucose and releasing stored glycogen. Adequate intake supports normal energy-yielding metabolism.
Mechanism of action
Neurotransmitter synthesis
B6 is needed for the biosynthesis of neurotransmitters, and it is involved in making GABA, the main calming signal in the brain. The authors of the anxiety trial suggest the drop in anxiety reflects stronger GABA-related inhibition, which has not been measured directly.
Hemoglobin formation
PLP is involved in hemoglobin formation, which is why B6 deficiency is associated with microcytic anemia.
Immune cell production
B6 promotes lymphocyte and interleukin 2 production; in a controlled diet study, removing B6 lowered both and restoring it brought them back to normal.
Homocysteine regulation
B6 helps maintain normal homocysteine levels. Lowering homocysteine with B vitamins did not reduce cardiovascular events in the HOPE-2 trial.
Energy metabolism
PLP and the related coenzyme PMP take part in amino acid metabolism, and PLP is also involved in one-carbon, carbohydrate and fat metabolism, including gluconeogenesis and glycogen breakdown.
Clinical trials
Double-blind, placebo-controlled trial of 100 mg B6 (pyridoxine HCl), 1000 µg B12 or placebo daily for about one month (Field et al. 2022, Hum Psychopharmacol).
478 young adults, mainly students; anxiety was assessed in 265 and depression in 146.
B6 reduced self-reported anxiety compared with placebo and showed only a trend toward lower depression scores. It strengthened a visual measure of neural inhibition but did not reliably change the other outcomes. The 100 mg dose equals the US upper limit and is above the European limit.
3-month placebo-controlled trial of 20 mg pyridoxine HCl daily (Deijen et al. 1992, Psychopharmacology).
76 healthy, self-supporting men aged 70 to 79 (38 on B6, 38 on placebo).
B6 improved memory, especially long-term memory; no positive effects were found on mood or other performance measures.
Systematic review and meta-analysis of randomized placebo-controlled trials (Wyatt et al. 1999, BMJ).
Nine published trials representing 940 women with premenstrual syndrome.
Odds ratio for improvement in overall premenstrual symptoms versus placebo was 2.32, and 1.69 for premenstrual depressive symptoms (four trials, 541 women). The authors said conclusions are limited by the low quality of most trials.
Randomized, double-blind, placebo-controlled trial of 25 mg B6 every 8 hours for 72 hours (Sahakian et al. 1991, Obstet Gynecol).
59 pregnant women with nausea (31 B6, 28 placebo).
In women with severe nausea, nausea scores fell more with B6 than placebo (P < .01); in those with mild to moderate nausea, and in the group as a whole, there was no significant difference. After 3 days, 8 of 31 on B6 versus 15 of 28 on placebo still had vomiting (P < .05).
Systematic review and meta-analysis of studies published before May 2021 (Jayawardena et al. 2023, Arch Gynecol Obstet).
18 studies of pyridoxine alone or combined with another active substance in pregnant women with nausea and vomiting.
B6 alone or combined with another active substance improved nausea on both the Rhode and PUQE scores in pooled analyses. Eight studies showed benefit with B6 alone and six with combinations.
Randomized, placebo-controlled trial of 2.5 mg folic acid, 50 mg B6 and 1 mg B12 daily for an average of five years (Lonn et al. 2006, N Engl J Med).
5,522 adults aged 55 or older with vascular disease or diabetes.
Homocysteine fell, but the primary outcome of cardiovascular death, heart attack or stroke did not differ (18.8% vs 19.8%, relative risk 0.95, P = 0.41). Fewer strokes and more hospitalizations for unstable angina occurred with the vitamins.