Vitamin B6 (pyridoxine hydrochloride) is a widely consumed vitamin with antioxidant properties. It has been associated with lower levels of biomarkers for cognitive decline including homocysteine and methylmalonic acid. Various studies have observed the effects of vitamin B6 on these disease biomarkers as well as the effect on cognitive performance.
Vitamin B6 (pyridoxine hydrochloride) is a widely consumed vitamin with various positive effects on cognition. The main effects are on memory, as well as general neuronal health and nerve conduction.
Is it safe? Are there side effects?
Vitamin B6 is approved as a dietary supplement component under provisions of the Dietary Supplement Health and Education Act of 1994. Vitamin B6 is a naturally occurring and is safe to consume (GRAS).
Consumption of vitamin B6 in safe quantities rarely leads to severe side effects in healthy people. Known side effects of vitamin B6 include nausea, vomiting, stomach pain, headache, tingling, and drowsiness.
Effects on Cognition
A number of cognitive studies have studied the effect of B6 on domains of cognition such as memory and executive function.
One study has found that supplementation with B6 for 12 weeks yielded a significant improvement in performance on a long term memory storage test in elderly men.1
A randomized, double-blind, placebo-controlled experiment found that supplementation of diet with vitamin B6 resulted in increased performance on short term memory tasks, namely the word recall task.2The study found that younger adults experienced an increased effect compared to older adults.
A study in 185 elderly men with vascular disease showed that ingestion of vitamin B6 led to improved performance in the Telephone Interview for Cognitive status (TICSm) test as well as the Letter Digit Coding Test.3
Homocysteine levels have been known to be inversely correlated to various aspects of cognitive function including memory. A study showed that B6 supplementation can lead to lower levels of homocysteine. However, the lower levels of homocysteine did not correlate with increased cognitive performance (memory as measured by Wechsler Paragraph Recall test, and executive function as measured by Part B of the Reitan Trail Making Test) in this case.4
Another study with 209 subjects found that supplementation with vitamin B6 led to lower levels of plasma homocysteine and serum methylmalonic acid (positive effect). There were also increases in performance performance on several cognitive tests for memory including identifical forms test, synonym test, digit symbol test, Thurstone’s picture memory test and figure classification test.5
A study showed that B6 supplementation can lead to lower levels of homocysteine. However, the lower levels of homocysteine did not correlate with increased cognitive performance (memory as measured by Wechsler Paragraph Recall test, and executive function as measured by Part B of the Reitan Trail Making Test) in this case.4
A study in 321 aging men showed that supplementation with vitamin B6 over a 3-year span resulted in improvements on the Figure Copying Task, which is normally a measure of executive function and a component of the Mini Mental Status Examination for dementia (see figure 1). Higher dosages generally correlated with greater improvements, with the most effective dosage being 3.1mg/day.6
Figure 1. Supplementation with vitamin B6 over a prolonged span was correlated with improvements in the figure copying score, a measure of executive function, in elderly adults.
Effects on Medical Conditions
Most of the medical research surrounding vitamin B6 centers around its effect on lowering disease biomarkers, such as homocysteine and methylmalonic acid.
High levels of homocysteine in the body have been correlated with increased risk of vascular disease. A study in 185 elderly patients with vascular disease showed that ingestion of vitamin B6 did not result in decreased homocysteine levels, but B12 ingestion did lead to decreased homocysteine.
Figure 2. Supplementation with vitamin B6 and B12 is associated with decreases in levels of inflammatory biomarkers for vascular dementia such as homocysteine, thromboxane and isoprostane.
A number of studies have observed the effects of B6 on cognitive function as well as levels of biomarkers linked to dementia in adults.
One study found that ingestion of B6 correlated with approximately 30% lower levels of homocysteine, a biomarker linked with dementia.7
Structure & Synthesis
Sources of vitamin B6 include meats and poultry (e.g. chicken, fish, tuna, salmon, milk, cheese), vegetables (e.g. spinach, carrots, beans) and grains (e.g. bran, wheat, brown rice).
Mechanisms of Action
Vitamin B6 needs to be converted to its active form, pyridoxal 5′-phosphate (PLP).