Dietary Vitamin Intake and Blood Biomarkers in Relation to Muscle Activation in Amyotrophic Lateral Sclerosis: A Cross-Sectional Study.

Background/Objectives: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive loss of motor function, which affects mobility and leads to secondary complications, including altered dietary intake due to dysphagia, fatigue, and hypermetabolism, particularly affecting vitamin consumption, which are essential micronutrients for neuromuscular performance. The specific relationship between vitamin intake and muscle activation is not well understood in patients with ALS; thus, it is relevant to identify blood biomarkers that reflect muscle status. Methods: A cross-sectional study was conducted with 61 patients with bulbar- or spinal-onset ALS. The dietary intake of B vitamins (B1, B2, B6, B12, folate, and niacin); vitamins C, A, D, and E; and the B6/protein ratio were assessed using a seven-day dietary record and a Food Frequency Questionnaire. Blood concentrations of butyrylcholinesterase (BuChE), albumin, haptoglobin, C-reactive protein (CRP), and paraoxonase 1 (PON1) were determined. Basal muscle activation was measured using surface electromyography of the biceps brachii, triceps brachii, rectus femoris, and tibialis anterior muscles. Two confirmatory predictive models were developed to evaluate the effects of muscle damage and vitamin intake on muscle strength. Results: Arm muscle activation was negatively predicted by the B6/protein ratio (β = -0.33). Leg activation was positively predicted by vitamin B9 (β = 0.39) and B6/protein (β = 0.17) and negatively predicted by vitamin A (β = -0.24). For biomarkers, albumin (β = 0.18) and PON1 (β = 0.28) positively predicted activation. For legs, albumin predicted activation (β = 0.31), whereas BuChE and haptoglobin predicted negative activation (β = -0.32 and β = -0.15, respectively). Conclusions: Weak associations were observed in patients with ALS: vitamin B9 intake showed a modest association with leg activation, the B6/protein ratio exhibited inconsistent associations across muscle groups, and vitamin A showed a negative association with leg activation. Albumin demonstrated the most consistent association as a potential biomarker of muscle function. These findings are exploratory and require validation in larger, longitudinal studies.