Inclusion Criteria:  Patients of both genders with a diagnosis of cystic fibrosis. FEV1 > 40%. Age between 6 and 18 years. Patients who grant their informed consent or whose representative grants informed consent to participate in the study.  Exclusion Criteria:  Pregnant or breastfeeding women Basal oxygen saturation <92% or household supplemental oxygen needs. Massive hemoptysis Patients who are not able to follow or who cannot be assessed in the study according to the protocol. Any circumstance that, at the discretion of the doctor, may involve a clinical risk or harm, the patient's participation in the study or that interferes with the evaluation of the same. Use of systemic glucocorticoids or in the 4 weeks prior to inclusion in the study. Use of non-steroidal anti-inflammatory drugs in the 2 weeks prior to inclusion in the study. Use of investigational drugs or participation in another clinical trial within 30 days prior to inclusion in the study or within the 5 elimination half-lives of the investigational drug. Be already supplementing with Omega -3, fish oil or DHA