Relationship of Low Vitamin B6 Status with Sarcopenia, Frailty, and Mortality: A Narrative Review.

Marginal vitamin B6 (B6) deficiency is a widespread global concern. Inadequate B6 levels have been linked to an increased risk of age-related chronic diseases such as cardiovascular diseases and cancers. In recent years, the growing concern over sarcopenia (the age-related loss of muscle mass and strength) and frailty (a decline in physiological resilience and increased vulnerability associated with aging) is particularly relevant due to the emergence of super-aged societies in developed countries. Notably, among the thirty-one studies included in this review, twenty-five showed a significant association of B6 status with sarcopenia, frailty, and all-cause mortality in adults (p < 0.05), while six showed no association. Emerging studies have suggested novel mechanisms underlying this association. These mechanisms involve P2X7 receptor-mediated NLRP3 inflammasome signaling, AMPK signaling, PD-L1 signaling, and satellite cell-mediated myogenesis. Furthermore, the modulation of PLP-dependent enzymes due to B6 deficiency is associated with impaired metabolic processes, affecting energy utilization, imidazole peptide production, and hydrogen sulfide production, as well as the kynurenine pathway, all of which play vital roles in skeletal muscle health and pathophysiology. This narrative review provides an up-to-date assessment of our current understanding of the potential role of nutritional B6 status in combating sarcopenia, frailty, and mortality.