OBJECTIVE It is well known that a low-status of B vitamins is associated with cognitive impairment. However, the impact of vitamin B6 (VB6) restriction on neurodegenerative diseases and its underlying mechanisms are rarely understood. This study investigated whether VB6 restriction aggravates neurodegeneration in mice fed either a low-fat (LF) control diet or a high-fat (HF) diet. METHODS Six-week-old male C57BL/6J mice were divided into 4 groups (LF7, LF1, HF7 and HF1) and fed either an LF diet [7 mg pyridoxine (PN)/kg diet], an LF with 1 mg PN/kg diet, an HF diet or an HF with 1 mg PN/kg diet for 16 weeks. Brain cortex and hippocampus were collected and used for the determination of biochemical parameters including VB6, lipid peroxides, and neurodegeneration-related mRNA and protein levels. RESULTS VB6 restriction reduced levels of the biologically active form of VB6, pyridoxal phosphate (PLP) in the brain. Low consumption of VB6 inactivated brain-derived neurotrophic factor signaling and cell proliferation, and induced oxidative stress, endoplasmic reticulum stress and apoptotic cell death. Significant correlation between brain lipid peroxide levels and PLP levels were observed. VB6 restriction also induced characteristic features of neurodegeneration such as amyloid-β deposition and tau hyperphosphorylation. Similarly, high-fat diet increased parameters associated with neurodegeneration. Aggravating effects of VB6 restriction were observed in both LF control and HF groups. CONCLUSIONS Dietary VB6 restriction plays a key role in neurodegeneration, and VB6 restriction worsens HF-induced neuronal damage in mice. Our study emphasizes the essential role of VB6 in maintaining brain health.