Inclusion Criteria COPD Patients:

• COPD patients with moderate to very severe disease stage according to GOLD criteria (i.e. GOLD stage II-IV);
• Medically stable.

Exclusion Criteria COPD Patients:

• Age <18 years;
• Allergy or intolerance to components of the study product;
• Not willing or not able to quit vitamin D or fatty acid supplement intake;
• Investigator's uncertainty about the willingness or ability of the patient to comply with the protocol requirements (e.g. leg amputation) or patients suffering from other acute or unstable chronic diseases that will compromise the study outcome (e.g. active cancer requiring treatment);
• Participation in any other study involving investigational or marketed products concomitantly or within four weeks prior to entry into the study;
• Patients with terminal illness;
• Recent hospital admission (<4 weeks prior to the start of the study);
• Temporary oral steroid or antibiotics use due to a COPD exacerbation in the last 4 weeks;
• Lung malignancy in the previous 5 years;
• Diagnosis of dementia or neurodegenerative disease (e.g., Alzheimer's disease, Parkinson's disease, Huntington's chorea, frontotemporal dementia) in the medical records;
• Recent diagnosis of cerebral conditions (<1 year e.g. cerebral infarction, hemorrhage, brain tumors, transient ischemic attack) in the medical records;
• Any medical condition that significantly interferes with digestion and/or gastrointestinal function (e.g. short bowel syndrome, inflammatory bowel disease, gastric ulcers, gastritis, (gastro)-enteritis, GI-cancer) as judged by the investigator.

Inclusion Criteria Healthy Controls

• Forced expiratory volume in 1 second/Forced vital capacity > 0.7;
• Medically stable.

Exclusion Criteria Healthy Controls

• Age <18 years;
• Investigator's uncertainty about the willingness or ability of the patient to comply with the protocol requirements (e.g. leg amputation) or patients suffering from other acute or unstable chronic diseases that will compromise the study outcome (e.g. active cancer requiring treatment);
• Participation in any other study involving investigational or marketed products concomitantly or within four weeks prior to entry into the study;
• Patients with terminal illness;
• Recent hospital admission (<4 weeks prior to the start of the study);
• Temporary antibiotics use in the last 4 weeks;
• Lung malignancy in the previous 5 years;
• Diagnosis of dementia or neurodegenerative disease (e.g., Alzheimer's disease, Parkinson's disease, Huntington's chorea, frontotemporal dementia) in the medical records;
• Recent diagnosis of cerebral conditions (<1 year e.g. cerebral infarction, hemorrhage, brain tumors, transient ischemic attack) in the medical records;
• Any medical condition that significantly interferes with digestion and/or gastrointestinal function (e.g. short bowel syndrome, inflammatory bowel disease, gastric ulcers, gastritis, (gastro)-enteritis, GI-cancer) as judged by the investigator.
• Diagnosis of any chronic lung disease.

History of severe allergic reactions to study medication Currently pregnant or breastfeeding Recent participation in another clinical trial within the last 30 days Presence of uncontrolled medical conditions that could affect safety