Abstract
Functional foods enriched with bioactive compounds-including vitamins, minerals, polyphenols, probiotics, fatty acids, and amino acids-have gained growing attention due to their ability to modulate immune responses. This review aims to summarize and critically evaluate evidence from both preclinical and clinical studies on the immunomodulatory effects of these compounds. A structured literature search was performed across major scientific databases in accordance with PRISMA 2020 guidelines. Seventy studies met the predefined eligibility criteria and were included. Evidence indicates that functional ingredients support immune function via antioxidant, anti-inflammatory, and microbiome-mediated pathways. Clinical trials further report benefits including a reduced risk of respiratory infections and enhanced vaccine responses. Nonetheless, important challenges remain regarding bioavailability, inter-individual variability, and the long-term safety of supplementation. Emerging research on precision nutrition and innovative delivery systems may further enhance the efficacy of these bioactive compounds. Overall, functional foods and nutraceuticals show strong potential as adjunct strategies for maintaining immune health; however, further well-designed clinical studies are required to confirm their translational applicability.