Targeting Oxidative Stress in Insulin-Resistant Postmenopausal Women: Effects of Resveratrol and Vitamin C on Oxidative Damage and Antioxidant Defenses in a Randomized Clinical Trial

Women experience significant changes throughout their lives, particularly during the transition from reproductive age to postmenopause, marked by hormonal imbalance and reduced estrogen production. This stage is associated with increased oxidative stress, which can contribute to cardiovascular issues and insulin resistance. This study aimed to assess the effects of resveratrol and vitamin C supplementation on 8-Isoprostane, a marker of oxidative stress, and on DNA damage, as indicated by 8-hidroxi-2′-desoxiguanosina (8-Oxo-dG), in postmenopausal women with insulin resistance, and to evaluate how these supplements modified antioxidant defense. A randomized, double-blind clinical trial was conducted. Plasma samples were analyzed to measure antioxidant enzyme activity, including superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione peroxidase (GPx), and to assess oxidative damage to lipids and DNA. Forty-two patients were recruited and randomly assigned to three treatment groups. Within-group analyses showed significant increases in CAT and GR activities and a reduction in plasma 8-isoprostane concentrations in the group receiving combined resveratrol and vitamin C supplementation, with increases of 12% in CAT activity (p = 0.008) and 84% in GR activity (p = 0.007), and a 34% reduction in 8-isoprostane concentrations (p = 0.01). However, no significant between-group differences or treatment × time interactions were observed. No significant changes were detected in 8-Oxo-dG concentrations. These preliminary findings suggest that antioxidant supplementation may influence selected markers of antioxidant defense and lipid oxidative damage in postmenopausal women with insulin resistance; however, the present study does not demonstrate the superiority of one supplementation regimen over the others.