Fortified Eggs as Food-Based Vehicles for Nutrient Delivery: A Scoping Review of Human Intervention Studies

Background/Objectives: Fortified eggs have been proposed as food-based vehicles for delivering micronutrients and other bioactive compounds. However, human intervention evidence remains fragmented across nutrient targets, populations, intervention designs, and outcome domains. This review mapped human intervention studies and summarized the reported nutritional and health-related outcomes associated with fortified egg consumption. Methods: PubMed, Embase, Web of Science, the Cochrane Library, CNKI, Wanfang Data, and SinoMed were searched for studies published in English or Chinese from 1 January 2005 to 1 June 2025. Eligible studies were human intervention studies evaluating fortified, enriched, or bio-enhanced eggs and reporting at least one nutritional or health-related outcome. Owing to substantial heterogeneity in nutrient type, intervention design, comparator, duration, and outcome assessment, findings were synthesized narratively. Results: Thirty-seven human intervention studies met the eligibility criteria. Most evaluated eggs enriched with n-3 polyunsaturated fatty acids, followed by carotenoid-enriched eggs, whereas relatively few examined iodine or other fortified nutrients. Across studies, fortified egg consumption was generally associated with improvements in intake estimates and biomarkers of targeted nutrient status, including circulating fatty acids, serum carotenoids, and, in a limited number of studies, urinary iodine. Evidence for downstream health-related outcomes was more limited, inconsistent, and difficult to compare across nutrient categories and study populations. Conclusions: Fortified eggs may serve as useful food-based vehicles for improving the delivery of selected nutrients and short-term nutrient-status biomarkers. However, the evidence base remains heterogeneous and nutrient-specific, and it is still uncertain whether these changes translate into consistent, clinically meaningful health benefits. Larger, longer-term, and more rigorously reported trials, particularly in populations at nutritional risk, are needed.