Introduction: Restrictive diets are increasingly encountered in pediatric practice and may be adopted voluntarily or prescribed for medical conditions. Although they can support normal growth when appropriately planned, exclusion of nutritionally important foods may increase the risk of nutrient inadequacy. This narrative review examined nutritional deficiencies and laboratory monitoring in children following plant-based, food-allergy elimination, gluten-free, ketogenic, and protein-restricted diets for inherited metabolic disorders. Methods: Targeted searches of PubMed, Scopus, and Web of Science were conducted through 30 June 2026 using pediatric, diet-specific, nutritional-status, and biomarker terms. Because this was a narrative review, the literature was selected and synthesized qualitatively rather than through a formal systematic-screening process; no fixed study count, duplicate independent screening, or formal risk-of-bias assessment was performed. Professional guidelines and position papers were prioritized when discussing monitoring considerations, while pediatric studies were used to describe dietary intake, biochemical findings, clinically manifest deficiency, and growth outcomes. Results: Nutritional risks differed according to the foods or nutrients restricted. Vitamin B12 and iron were major concerns in plant-based diets, whereas cow’s milk and multiple-food elimination increased the risk of inadequate calcium, vitamin D, iodine, protein, and energy intake. Gluten-free diets were commonly associated with low fiber, iron, folate, and B-vitamin intake, particularly when refined, non-fortified products predominated. Ketogenic dietary therapy required attention to selenium, vitamin D, bone-related minerals, carnitine in selected patients, and linear growth. In phenylketonuria and related disorders, nutritional adequacy depended strongly on protein-substitute adherence and appropriate provision of essential amino acids and micronutrients. Across all dietary patterns, laboratory results required interpretation in relation to dietary intake, growth, supplementation, inflammation, medication, and the underlying condition. Across dietary patterns, inadequate intake, biochemical abnormalities, clinically manifest deficiency, and impaired growth were considered related but distinct outcomes. Conclusions: Nutritional monitoring should be individualized and based on the actual dietary restriction and clinical risk. The principal contribution of this review is a practical, risk-based framework that links the specific dietary restriction and adequacy of replacement foods with growth, symptoms, supplementation, and targeted laboratory biomarkers.

Background: Population aging is accompanied by progressive immune remodeling, chronic low-grade inflammation, and increased susceptibility to neurodegenerative diseases. Although the microbiota–gut–brain axis is increasingly recognized as a regulator of neuroimmune homeostasis, mechanisms linking age-associated dysbiosis with immunosenescence, barrier dysfunction, and brain aging remain incompletely understood. This review integrates current evidence into the proposed Gut–Immune–Brain Resilience Axis (GIBRA), a systems-level model describing how microbial signaling shapes neuroimmune resilience during aging. Methods: A structured narrative review was conducted using PubMed and the Web of Science Core Collection from database inception up to July 2026. Evidence from systematic reviews, meta-analyses, consensus statements, mechanistic and translational studies, longitudinal cohorts, randomized clinical trials, and observational studies was synthesized. Results: Current evidence supports an important role for the disruption of microbial functional signaling in neuroimmune aging, while microbial taxonomy and functional profiles provide complementary levels of biological information. Reduced short-chain fatty acid production, dysregulated tryptophan metabolism, microbial translocation, endotoxin-mediated innate immune activation, and gut-conditioned adaptive immune responses promote immunosenescence, inflammaging, barrier dysfunction, and microglial priming. The proposed Double-Barrier Hypothesis links intestinal and blood–brain barrier dysfunction as complementary mechanisms underlying chronic neuroinflammation. GIBRA highlights functional microbiome endotypes, biomarkers, multi-omics, and artificial intelligence as emerging tools for precision medicine. Conclusions: GIBRA provides an integrated systems biology perspective connecting microbial signaling, immune resilience, barrier integrity, and brain resilience during aging. Prioritizing functional resilience over microbial taxonomy may improve biomarker discovery, patient stratification, and microbiome-targeted interventions for neurodegenerative disease prevention. Prospective longitudinal studies integrating multi-omics are needed to support clinical translation.

Background/Objectives: Pharmacogenetics examines genome variability and its influence on drug efficacy and toxicity, forming the foundation for personalized medicine. Patients with inflammatory bowel disease (IBD) treated with azathioprine with thiopurine S-methyltransferase (TPMT) deficiency are at an increased risk of drug-related toxic effects. Variability in the HLA-DQA1 and DQB1 alleles may lead to an inadequate therapeutic response. This study aimed to determine the significance of TPMT and HLA-DQ Allelic Variants in therapy optimization planning. Methods: A retrospective study was conducted to determine TPMT gene polymorphism and the presence of HLA-DQA1 and HLA-DQB1 alleles in children diagnosed with IBD and treated at the Institute for Child and Youth Health Care of Vojvodina in May 2023. Results: The study included 104 children with a mean age of 13.71 ± 3.1 years, with a balanced gender distribution. A TPMT mutation was identified in only one child. The most common HLA-DQA1 alleles were *01 (49%) and *05 (28.8%), while the most frequent allele at the HLA-DQB1 locus was 03 (15.4%). The presence of the HLA-DQA105 allele was associated with the development of anti-drug antibodies against anti-TNF therapy (RR: 1.23; 95% CI: 1.03–1.50), while the presence of HLA-DQA101 was significantly more frequent in children on optimized therapeutic regimens (RR: 1.63; 95% CI: 1.13–2.10). Conclusions: Prior to the initiation of azathioprine therapy, TPMT genotyping should be performed to prevent adverse effects and ensure optimal drug dosing. Identification of the HLA-DQA105 and HLA-DQA101 alleles plays an important role in the planning of biological therapy regimens, including decisions on dose escalation or interval shortening.

Background/Objectives: Postbiotics are increasingly recognized as biologically active products of microorganisms with emerging potential as microbiome-inspired therapeutic interventions. While most microbiome-based strategies focus on modifying microbial composition, restoration of microbial signaling has received comparatively less attention. This review examines postbiotics through the lens of microbial signaling restoration and proposes a unified Metabolite–Immune–Redox (MIR) axis linking microbial-derived signals with immune regulation, redox homeostasis, endothelial integrity, and host resilience. Methods: This narrative review synthesizes current evidence on postbiotics, microbial metabolites, structural microbial components, and extracellular vesicles, with emphasis on their roles in immunometabolic regulation, redox biology, endothelial function, and host-directed interventions. Results: Current evidence suggests that short-chain fatty acids, indole derivatives, bile acid metabolites, and microbial extracellular vesicles are important mediators of host–microbe communication. These signals influence interconnected pathways involving mitochondrial function, inflammasome activity, immune calibration, endothelial and glycocalyx homeostasis, and disease tolerance. The review highlights the endothelium as an underrecognized therapeutic target and discusses biomarkers, including soluble thrombomodulin, von Willebrand factor, and D-dimer, as potential tools for identifying patients most likely to benefit from host-directed interventions. Major translational challenges include product heterogeneity, incomplete mechanistic characterization, uncertain exposure–response relationships, and unresolved regulatory considerations. Conclusions: The proposed MIR axis provides a hypothesis-generating framework for understanding how restoration of microbial signaling may contribute to precision host-directed therapeutic strategies. Further mechanistic and clinical studies are needed to validate this concept and define its translational potential in inflammatory, infectious, and critical illness settings.

Background/Objectives: Adolescent nicotine use increasingly extends beyond cigarettes to e-cigarettes, heated tobacco products and oral nicotine. This study aimed to characterize nicotine-product use, knowledge, risk perceptions and associated factors among final-year secondary-school students in Novi Sad, Serbia. Methods: A cross-sectional online survey was conducted among 205 students aged ≥18 years from general, medical and vocational schools in April–June 2026. Current use of cigarettes, e-cigarettes, IQOS, snus and waterpipe was self-reported without a fixed recall period, alongside knowledge, perceived harmfulness and social context. Exploratory multivariable logistic regression identified correlates of current use. Results: Overall, 49.3% of respondents (95% CI 42.5–56.1) reported current use of at least one product. IQOS was the most frequently used product (32.7%), followed by e-cigarettes (25.9%) and cigarettes (24.9%). Close-friend use was associated with higher odds of current use (adjusted odds ratio [aOR] 8.09 per category; 95% CI 3.36–19.51), whereas higher physical activity (aOR 0.43; 95% CI 0.26–0.72) and perceived harmfulness (aOR 0.42; 95% CI 0.19–0.94) were associated with lower odds. Knowledge scores did not differ by current use. Conclusions: Nicotine-product use, particularly of heated tobacco products and e-cigarettes, was common in this convenience sample. Current use was associated with close-friend use and lower perceived harmfulness, most clearly for cigarettes and IQOS, but not with factual knowledge. Prevention efforts may need to go beyond knowledge transfer and consider the peer context and perceptions of specific products.