Selegiline

Low vitamin B6 status can promote accumulation of homocysteine, a sulfur‑containing amino acid that can damage the endothelium, increase oxidative stress, and promote clot formation, all of which are relevant to cardiovascular disease and stroke. Large observational studies and cross‑sectional analyses have shown that people with lower plasma pyridoxal‑5‑phosphate (active B6) levels have higher rates of stroke and other vascular events, and in some cohorts low B6 was a stronger predictor of stroke or transient ischemic attack than homocysteine itself. The encouraging finding from meta‑analyses and clinical trials is that B‑vitamin combinations including B6 can lower homocysteine and modestly reduce the combined risk of stroke, myocardial infarction, and vascular death in high‑risk patients, suggesting that maintaining adequate B6 is one useful piece of broader cardiovascular prevention

In the brain, vitamin B6 (pyridoxine) is needed to produce neurotransmitters and to keep homocysteine in check, so low B6 status has been linked to both depressed mood and subtle cognitive problems such as slower processing and poorer attention in some adults. Observational work in older populations suggests that lower blood levels or intakes of B6 tend to track with worse performance on memory, executive‑function, and psychomotor‑speed tests, raising concern that marginal B6 status may contribute to age‑related cognitive decline. Clinically, when B6 deficiency coexists with depression, correcting it is viewed as one modifiable factor that may help support clearer thinking and better cognitive function alongside standard psychiatric and lifestyle treatments.

In the nervous system, vitamin B6 is essential for making the inhibitory neurotransmitter GABA, so significant deficiency can lower seizure threshold and lead to seizures or encephalopathy, particularly in infants but occasionally in adults. Classic pyridoxine‑dependent or B6‑responsive seizure syndromes in infants often present with refractory seizures that improve dramatically after B6 or pyridoxal‑5‑phosphate is given, highlighting how crucial this pathway is for brain stability. Clinically, this means that in patients, especially infants, with otherwise unexplained or treatment‑resistant seizures or encephalopathy, assessing and correcting B6 status is a low‑risk, potentially lifesaving step that should be considered early.

In the brain, vitamin B6 (pyridoxine) is a cofactor for enzymes that make key neurotransmitters such as serotonin, dopamine, and GABA, so low B6 status can contribute to depressive symptoms, irritability, and increased stress sensitivity. Epidemiologic studies in older adults and other populations have found that low plasma pyridoxal‑5‑phosphate (the active B6 form) or lower dietary B6 intake is associated with higher depression scores and roughly doubled odds of having clinically significant depressive symptomatology. The encouraging finding from emerging trials is that, in people with low or marginal B6 status, supplementation can modestly improve measures of anxiety and depressed mood, especially when used as part of a broader treatment plan that also addresses sleep, stress, and other nutrient deficiencies.

In some adults, vitamin B6 deficiency can manifest as a distal, symmetric peripheral neuropathy that is predominantly sensory rather than motor, with numbness, tingling, or burning pain starting in the feet and hands. Clinical descriptions note that this large‑fiber neuropathy often produces loss of vibration and position sense with relatively preserved pain and temperature sensation, which can lead to sensory ataxia and gait unsteadiness in more advanced cases. The practical point is that, because both B6 deficiency and excess can cause peripheral neuropathy, it is important to assess B6 status in patients with otherwise unexplained distal sensory symptoms and to correct deficiencies.

Because vitamin B6 is a required cofactor for the first step of heme synthesis, deficiency can impair hemoglobin production and lead to anemia that is sometimes microcytic or shows sideroblastic features on bone‑marrow exam. Case reports and series describe patients with otherwise unexplained microcytic, hypochromic or sideroblastic anemia, including ringed sideroblasts, who were ultimately found to have B6 deficiency and experienced normalization of hemoglobin after pyridoxine supplementation. The practical point is that vitamin B6 deficiency is an important, often overlooked, reversible cause of anemia in adults, so it is worth checking B6 status when the anemia pattern does not line up with iron, folate, or B12 results, or when those levels are normal but the anemia persists.