This study investigates the relationship between the Composite Dietary Antioxidant Index (CDAI) and biological aging, using data from the National Health and Nutrition Examination Surveys (NHANES) conducted between 2001 and 2018. The CDAI is a metric that assesses an individual's antioxidant profile based on dietary intake of various antioxidants. Biological age was determined using the PhenoAge algorithm, which incorporates chronological age and clinical biomarkers. The study found a significant inverse relationship between CDAI and biological age, indicating that higher CDAI scores are associated with delayed biological aging. Each standard deviation increase in CDAI was linked to a 0.18-year decrease in biological age. This relationship was consistent across different subgroups, including age, gender, race, income, physical activity, smoking status, and BMI. The findings suggest that dietary antioxidants play a crucial role in promoting healthy aging and reducing the risk of age-related diseases. The study provides valuable insights for public health initiatives aimed at promoting healthy aging through dietary interventions.This study investigates the relationship between the Composite Dietary Antioxidant Index (CDAI) and biological aging, using data from the National Health and Nutrition Examination Surveys (NHANES) conducted between 2001 and 2018. The CDAI is a metric that assesses an individual's antioxidant profile based on dietary intake of various antioxidants. Biological age was determined using the PhenoAge algorithm, which incorporates chronological age and clinical biomarkers. The study found a significant inverse relationship between CDAI and biological age, indicating that higher CDAI scores are associated with delayed biological aging. Each standard deviation increase in CDAI was linked to a 0.18-year decrease in biological age. This relationship was consistent across different subgroups, including age, gender, race, income, physical activity, smoking status, and BMI. The findings suggest that dietary antioxidants play a crucial role in promoting healthy aging and reducing the risk of age-related diseases. The study provides valuable insights for public health initiatives aimed at promoting healthy aging through dietary interventions.