Abstract
BACKGROUND: Oxidative stress has been implicated in aging and metabolic dysfunction, modulated by diet, lifestyle, and body composition. While structured dietary practices such as intermittent fasting and plant-based regimens have demonstrated antioxidative benefits, the biological impact of long-term religious fasting remains underexplored. Orthodox Christian fasting, characterized by periodic abstention from animal products and alignment with circadian rhythms, offers a unique naturalistic model for examining redox adaptation in humans. OBJECTIVES: To identify the physiological and biological factors of oxidative stress markers in Orthodox Christian monastic women compared to age-matched controls, focusing on the roles of adiposity, insulin, vitamin D status, and age. DESIGN: In this cross-sectional study, 52 Orthodox nuns and 56 women from the general population were assessed. METHODS: Serum levels of total antioxidant capacity (TAC), reduced glutathione (GSH), and thiobarbituric acid reactive substances were measured. Anthropometric indices (body mass index, body fat percentage, visceral fat), fasting insulin, 25-hydroxyvitamin D (25(OH)D), and age were recorded. Statistical analyses included group comparisons, Spearman correlations, and multivariable linear regression models. RESULTS: In the monastic group, body fat percentage (beta coefficient = 0.387, p = 0.003) and age (beta coefficient = 0.301, p = 0.014) were associated with TAC levels. Among controls, insulin positively correlated with GSH (ρ = 0.480, p < 0.001) and marginally inversely with TAC (ρ = -0.321, p = 0.060). No significant associations were found between 25(OH)D and oxidative markers in either group. CONCLUSIONS: Vitamin D and insulin levels were not significantly associated with oxidative stress markers in this cohort. These findings highlight the potential of long-term, culturally structured fasting to modulate redox homeostasis and suggest a complex interplay between age, adiposity, and antioxidant defenses. These findings should be interpreted within the context of a highly specific religious and cultural lifestyle and may not be generalizable to other populations. Further research is needed to elucidate underlying mechanisms and long-term clinical implications.