This randomized controlled clinical trial included 60 pediatric patients with cystic fibrosis (CF) assigned randomly into two arms; Arm 1(extra care arm):received a tailored dietary plan following Mediterranean diet to cover macronutrients needs according to recommended daily allowance (RDA) for age, with antioxidant supplements in specific doses in oral liquid form (200 mg vitamin E, 300 mg vitamin C, 90 μg Se, 500 μg vitamin A, 30 mg zinc, 3 mg copper and 2000 IU vitamin D) for 6 months. Arm 2: recieved tailored dietary plan following Mediterranean diet as Arm 1 with fat soluble vitamins supplementation (150 μg vitamin A, 2000 IU vitamin D, 100 mg vitamin E and 1000 μg vitamin K) for 6 months. This study aimed to evaluate the effect of antioxidants supplementation on the level of oxidative stress, as measured by 3-Nitrotyrosine, bacterial colonization and diseases severity among CF children.

Inclusion Criteria:

• Patients with documented diagnosis of cystic fibrosis (CF) who were diagnosed according to CF Foundation guidelines based upon positive sweat tests and/or the presence of a mutation in the homozygous state or two heterozygous mutations on the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein

Exclusion Criteria:

• Patients with current pulmonary exacerbations.
• Patients with severe sepsis.
• Patients with comorbid systemic illnesses.