The thyroid gland plays a crucial role in regulating metabolism and supporting development through the production of the hormones T4 and T3. These hormones are essential during childhood for nervous system myelination, physical growth, puberty, skeletal and dental maturation, and overall metabolic balance. In early infancy, when the hypothalamic–pituitary–thyroid axis is still immature, thyroid dysfunction can result in a range of long-term complications. The metabolism and action of thyroid hormones depend not only on iodine but also on other vital micronutrients, particularly selenium (Se). This narrative review aims to comprehensively examine the role of selenium in maintaining thyroid health from fetal life through adolescence. Selenium is a key micronutrient involved in thyroid development, hormone synthesis, antioxidant defense, and immune regulation, especially during pregnancy and childhood. Inadequate selenium levels may contribute to the onset, progression, and clinical management of various thyroid disorders, particularly hypothyroidism and autoimmune thyroid diseases. Although scientific evidence supports selenium’s critical functions in hormone metabolism and antioxidant protection, public awareness and monitoring of selenium intake remain insufficient. Beyond the need for further research, there is an urgent call for integrated public health strategies, ranging from sustainable, food-based approaches to targeted clinical screening and educational programs. Promoting awareness of selenium’s importance and incorporating selenium status into maternal and pediatric care protocols could play a significant role in preventing deficiencies and supporting long-term endocrine and neurodevelopmental health.

Human breast milk (HBM) is considered the gold standard for infant nutrition due to its optimal nutrient profile and complex composition of cellular and non-cellular components. Breastfeeding positively influences the newborn’s gut microbiota and health, reducing the risk of conditions like gastrointestinal infections and chronic diseases (e.g., allergies, asthma, diabetes, and obesity). Research has revealed that HBM contains beneficial microbes that aid gut microbiota maturation through mechanisms like antimicrobial production and pathogen exclusion. The HBM microbiota composition can be affected by several factors, including gestational age, delivery mode, medical treatments, lactation stage, as well as maternal lifestyle habits (e.g., diet, physical activity, sleep quality, smoking, alcohol consumption, stress level). Particularly, lifestyle factors can play a significant role in shaping the HBM microbiota by directly modulating the microbial composition or influencing the maternal gut microbiota and influencing the HBM microbes through the enteromammary pathway. This narrative review of current findings summarized how maternal lifestyle influences HBM microbiota. While the influence of maternal diet on HBM microbiota is well-documented, indicating that dietary patterns, especially those rich in plant-based proteins and complex carbohydrates, can positively influence HBM microbiota, the impact of other lifestyle factors is poorly investigated. Maintaining a healthy lifestyle during pregnancy and breastfeeding is crucial for the health of both mother and baby. Understanding how maternal lifestyle factors influence microbial colonization of HBM, along with their interactions and impact, is key to developing new strategies that support the beneficial maturation of the infant’s gut microbiota.

Objective: This narrative review summarizes current evidence on the associations between ultra-processed food (UPF) consumption, childhood and adolescent obesity, and functional gastrointestinal disorders (FGIDs), and examines the metabolic, inflammatory, microbial, and gut–brain mechanisms underlying these links. Methods: A comprehensive search of PubMed and Scopus identified articles published between January 2010 and September 2025. Eligible studies included human research in individuals aged 0–18 years; adult studies were considered when contributing relevant mechanistic insights. Of 335 records screened, 112 studies met the inclusion criteria and were synthesized narratively according to methodological appropriateness. Results: High UPF intake was consistently associated with increased adiposity, metabolic dysregulation, and greater cardiometabolic risk in youth. Children with overweight or obesity showed a higher prevalence of FGIDs compared with their normal-weight peers. Mechanistic evidence suggests that UPFs, rich in refined carbohydrates, unhealthy fats, and additives, may promote gut microbiota dysbiosis, impair intestinal barrier integrity, alter motility, and induce low-grade inflammation, thereby disrupting gut–brain signaling and contributing to FGID symptoms. Early-life and maternal UPF exposure may further increase susceptibility to metabolic and gastrointestinal disturbances through epigenetic and microbiome-mediated pathways. Conclusions: UPFs emerge as a shared etiological factor for obesity and FGIDs in childhood. This review contributes an integrated synthesis of epidemiological and mechanistic data while highlighting key research gaps, particularly the need for standardized methodologies and pediatric interventional studies to strengthen the evidence base.

Background/Objectives: Inadequate gestational weight gain (GWG), encompassing both low and excessive, is a significant concern because of its association with adverse maternal and neonatal health outcomes. The relationships between maternal lifestyle factors, such as diet, physical activity, prepregnancy body mass index (BMI), and GWG, are complex. This study aims to explore these associations via correspondence analysis (CA), a method that visualizes the relationships between categorical variables. Methods: A CA was conducted using baseline data from the ongoing LIMIT (Lifestyle and Microbiome Interaction Early Adiposity Rebound in Children) prospective cohort study. The analysis included 162 subjects whose complete maternal characteristic data were available to explore associations between maternal features and GWG. Results: The results were visualized through a two-dimensional graphical representation, with the related statistical measures. The horizontal axis of the CA map captures 63.4% of the total inertia of the data, and the vertical axis captures 36.6%. Maternal profiles with lower education, smoking, high meat consumption, and prepregnancy overweight or obesity showed a higher prevalence of excess GWG than did the average profile. Compared with the average profile, medium Mediterranean diet adherence was associated with a greater prevalence of low GWG and underweight and obese mothers with adequate GWG. Conclusions: This study identifies maternal lifestyle factors, such as diet and physical activity, as key determinants of GWG, with excess GWG linked to unhealthy behaviors. Tailored interventions focusing on prepregnancy BMI and dietary habits could optimize pregnancy outcomes. Personalized prenatal care is essential for managing GWG and improving maternal health.