## 6 Nutrient Interactions and Personalized Nutrition Strategies  
The biological effects of nicotinamide and pyridoxine do not occur in isolation; rather, they are modulated by their interactions with other nutrients and lifestyle factors. These interactions can amplify their effects on muscle metabolism, stem cell function, and systemic health, especially when incorporated into personalized nutrition strategies [188, 189, 190]. A growing body of research supports the concept of nutrient synergy in muscle health. For instance, combining nicotinamide with resistance exercise enhances NAD\({}^{+}\) biosynthesis andmitochondrial adaptations. Nicotinamide supplementation increases SIRT1 activity, while exercise-induced NAMPT expression synergistically boosts NAD\({}^{+}\) salvage [54; 191; 192; 193]. Similarly, pyridoxine interacts with branched-chain amino acids and micronutrients like magnesium and folate to improve amino acid metabolism, methylation reactions, and redox balance. Multinutrient supplementation trials in frail elderly populations show that B6, when combined with adequate protein, vitamin D, and omega-3 fatty acids, is associated with improved muscle strength, reduced inflammation, and slower lean mass loss [85; 155; 156; 188]. This suggests that co-formulation and dietary pattern design are key to maximizing efficacy. Moreover, the food matrix and timing of intake influence the bioavailability and metabolic fate of both B3 and B6, indicating the importance of holistic nutritional planning. The development of precision nutrition approaches offers new opportunities for tailoring interventions based on individual nutritional phenotypes and risk profiles. Biomarkers such as plasma PLP, urinary NMN, CRP, and body composition indices can guide personalized plans [194; 195; 196; 197]. Stratifying patients by sex, metabolic status, and inflammatory burden may enhance the effectiveness of B3/B6 supplementation. Additionally, elderly individuals with chronic conditions or post-hospitalization recovery may benefit from customized combinations of dietary and lifestyle interventions. Integrating vitamin B3 and B6 supplementation with resistance training, high-quality protein intake, and anti-inflammatory dietary patterns could restore regenerative capacity and improve quality of life. Altogether, nutrient interactions and personalized nutrition represent a promising direction for harnessing the full potential of nicotinamide and pyridoxine in combating sarcopenia. This multifaceted strategy leverages dietary complexity, metabolic individuality, and molecular biology to support muscle health in aging populations [1; 2; 185; 19; 18] (Figure 5).  
Figure 5: Integrative framework for the role of nicotinamide (B3) and pyridoxine (B6) in skeletal muscle regeneration. This conceptual diagram illustrates a multifactorial strategy through which nicotinamide and pyridoxine support muscle regeneration and help counteract sarcopenia. Nicotinamide interacts synergistically with resistance exercise to enhance NAD\({}^{+}\) synthesis via the SIRT1-NAMPT pathway, while pyridoxine acts in concert with amino acids and micronutrients to improve redox balance and metabolic regulation. Key factors such as the food matrix, timing of intake, and delivery form influence vitamin uptake and bioefficacy. Precision nutrition approaches, guided by biomarkers (e.g., PLP, NMN, and CRP) and individual phenotypic profiling, enable targeted intervention design. Integration with lifestyle factors such as resistance training, anti-inflammatory dietary patterns, and adequate protein intake further amplifies the regenerative impact. This framework highlights the importance of combining molecular, nutritional, and behavioral components for optimal muscle health in aging.