Dimitrios Papandreou

Introduction: Metabolic syndrome (MetS) is a cluster of cardiometabolic abnormalities including central obesity, dysglycemia, hypertension, and dyslipidemia. Vitamin D deficiency is highly prevalent among adults with MetS and may contribute to insulin resistance, inflammation, and adverse lipid profiles. Although vitamin D supplementation has been reported to improve MetS parameters, limited information is available on whether these effects differ by baseline vitamin D status or supplementation dose, information essential for clinical decision-making. Methods: This systematic review evaluated the effect of oral vitamin D supplementation on MetS components in adults and examined whether treatment effects appeared differ according to baseline vitamin D status and supplementation dose. A comprehensive search of PubMed/MEDLINE, Embase, Web of Science, and CENTRAL was conducted following PRISMA guidelines. Given the anticipated clinical and methodological heterogeneity across eligible trials, a narrative synthesis rather than meta-analysis was planned a priori. Risk of bias was assessed using the Cochrane Collaboration Risk of Bias Tool. Eligible RCTs included those evaluating oral vitamin D supplementation for at least 8 weeks in adults diagnosed with metabolic syndrome or presenting at least 3 of 5 MetS components. In addition, comparator groups included placebo or dietary-instruction-only controls. Outcomes of interest included waist circumference, triglycerides, HDL-cholesterol, blood pressure, fasting glucose, homeostatic model assessment of insulin resistance (HOMA-IR), glycated hemoglobin (HbA1c), and body mass index (BMI). Results: Eight randomized controlled trials (634 participants) met the full eligibility criteria and were included in the narrative synthesis. Vitamin D supplementation consistently increased serum 25(OH)D concentrations across trials. Significant improvements were reported in triglycerides and insulin resistance indices in a subset of trials, and in selected inflammatory markers, waist circumference, and BMI in individual studies, while blood pressure, HDL-cholesterol, and fasting glucose showed no consistent change across the majority of trials. Findings were most favorable among participants with baseline vitamin D deficiency and in trials using higher supplementation doses, although these patterns are exploratory, as no trial was powered for formal subgroup comparison. Risk-of-bias assessment indicated that seven of the eight evaluated trials had some concerns or high risk of bias in at least one domain, limiting the overall certainty of the evidence. Conclusions: Vitamin D supplementation shows slight benefit for specific MetS components, particularly among vitamin D-deficient adults, but effects were inconsistent across trials and metabolic parameters. Substantial variability in study design, dosing strategies, and population characteristics limits definitive conclusions. Adequately powered, standardized randomized trials are needed to clarify vitamin D's role in metabolic syndrome management. Systematic review registration: CRD420261421121.

Introduction: Older adults face multiple challenges in meeting their daily energy, protein, and fluid requirements. These challenges adversely affect metabolic function, gastrointestinal health, muscle mass, and sensory perception. Malnutrition and appetite loss remain highly prevalent despite increasing clinical recognition and are often underdiagnosed in clinical practice. This narrative review aims to understand the prevalence of appetite loss and malnutrition in older adults and their combined effects on dietary intake, nutritional status, and body composition. It also addresses methodological considerations and highlights evidence-based strategies for diagnosis, management, and prevention. Methodology: A structured literature search was conducted across major scholarly databases to identify related studies published between 2015 and 2025. Results: Malnutrition prevalence ranged from 3% to 36%, while poor appetite affected 8% to 30% of older adults across different settings. A bidirectional cycle was observed. Appetite loss contributes to inadequate calorie and protein intake, micronutrient deficiencies, and weight loss. Malnutrition further exacerbates appetite reduction by inducing inflammation, sensory impairment, muscle wasting, adverse medical outcomes, and social factors. Both disorders were associated with reduced mobility, sarcopenia, cognitive decline, extended hospital stays, increased rehabilitation needs, and higher mortality. Multiple studies also identified “hidden malnutrition” in older adults with normal or high BMI without considering the malnutrition level. Discussion: The findings highlight the bidirectional relationship between appetite loss and malnutrition. They also reveal the limited incorporation of appetite assessment into routine clinical practice and significant gaps in current screening approaches. Conclusion: Identifying health problems and tailoring appropriate nutritional interventions in older adults, such as protein modification and a tailored diet plan, will provide effective appetite screening and nutrition support. Evidence indicated a close interconnected relationship between malnutrition and appetite loss. Addressing these concerns will support healthier aging.

Background/objective: Postpartum depression (PPD) is a significant public health issue affecting about 19% of mothers globally. It has well-documented impacts on maternal well-being, mother–infant relationships, and child developmental outcomes. At the same time, the level of vitamin D deficiency in women of reproductive age is very high (affecting 60–87 percent of pregnant women globally). The review aims to synthesize current evidence and highlight priority research areas to improve maternal mental health outcomes. Methods: A systematic literature search of PubMed, Scopus, and Google Scholar (2015–2026) was conducted, followed by narrative synthesis of mechanistic, observational, and interventional evidence. Results: Adequate vitamin D status may contribute to a reduced risk of postpartum depression through multiple interacting pathways, including serotonin synthesis and metabolism (via tryptophan hydroxylase 2 (TPH2) and monoamine oxidase-A (MAO-A) regulation), neuroplasticity via brain-derived neurotrophic factor (BDNF) signaling, and suppression of the pro-inflammatory cytokine cascade. Dose–response meta-analyses and large prospective cohort studies indicate consistent negative relationships between maternal vitamin D levels and postpartum depressive and anxiety symptoms with optimal serum 25-hydroxyvitamin D (25(OH)D) levels of 90–110 nmol/L. Conclusions: There is still limited evidence on the intervention; it is still methodologically diverse, and only a few randomized controlled trials have been carried out on specifically postpartum populations.

Gestational Weight Gain (GWG) affects maternal and fetal health. Vitamin D insufficiency, common during pregnancy, may impact weight control via metabolic, inflammatory, and endocrine pathways. However, the association between maternal vitamin D and GWG remain unclear. Therefore, this narrative review's objective is to integrate existing evidence on the correlations between maternal vitamin D and GWG, examine the effect of pre-pregnancy Body Mass Index (BMI), assess the cumulative effects of vitamin D deficiency and inadequate GWG on pregnancy outcomes, and assess the efficacy of vitamin D supplementation. A narrative review was conducted in accordance with SANRA 2.0 principles, with the search strategy reported in line with PRISMA-S guidance. A literature review was conducted in PubMed, Scopus, and Google Scholar to identify studies examining gestational weight gain (GWG) and serum 25-hydroxyvitamin D status published between January 2015 and November 2025. Observational and interventional studies were eligible for inclusion. After eliminating duplicates, reviewers independently evaluated 1,395 records; 14 studies were included. The prevalence of vitamin D deficiency and its bidirectional associations with maternal weight, gestational weight gain as a modifier of vitamin D's metabolic effects, combined effects on fetal and offspring outcomes, and supplementation trial evidence were narratively synthesized. Vitamin D insufficiency affected 30-85% of pregnant women worldwide. Bidirectional vitamin D-GWG relationships differed among studies, with prepregnancy BMI as a substantial effect modifier. In overweight women, low first trimester vitamin D levels were associated with 3.70 kg higher total GWG. Vitamin D's insulin resistance protection was greatly reduced by excessive GWG. High-dose supplementation (1600 IU/day) met biochemical needs but did not affect GWG. In one cohort, both low vitamin D and suboptimal GWG independently predicted small-for-gestational-age births. The association between maternal vitamin D status and gestational weight gain remains inconsistent across the current evidence base. Pre-pregnancy BMI may modify this relationship, with the strongest associations observed among overweight and obese women. Integrated strategies addressing both vitamin D adequacy and appropriate gestational weight gain, particularly among women with elevated pre-pregnancy BMI, should be explored in future research.

Background/Objectives: The Nutrition Care Process (NCP) is a standardized model designed to improve the quality and consistency of nutrition care. However, its implementation remains variable across settings, influenced by factors such as time constraints, training, peer support, and technological infrastructure. This systematic review aims to synthesize the available evidence on barriers and facilitators influencing the implementation of the NCP/NCPT and to explore how different documentation formats may influence its adoption. Methods: This systematic review was conducted in accordance with PRISMA 2020 guidelines and included peer-reviewed studies published between 2009 and 2024 in English or Greek. Searches were conducted in MEDLINE, EMBASE, Scopus, CINAHL, and the Cochrane Library. Study quality was assessed using the National Heart, Lung, and Blood Institute (NIH) tool. A total of 11 reports representing eight studies were included, comprising cross-sectional, cohort, qualitative, and pilot designs. Results: The most commonly reported barriers to NCP implementation were lack of training, time constraints, and limited technological infrastructure. Key facilitators included support from national dietetic associations, peer collaboration, and access to electronic health records (EHRs). Electronic formats were more frequently described as supporting improved documentation practices, practitioner confidence, and workflow efficiency, whereas manual approaches were commonly reported as time-consuming and less structured. Conclusions: Digital integration of the NCP may support more consistent documentation practices and improved workflow processes; however, the current evidence is largely observational and heterogeneous. Evidence regarding patient-level outcomes remains limited, and definitive conclusions regarding the comparative effectiveness of implementation formats cannot be drawn. Further high-quality research is needed to evaluate the long-term clinical impact of NCP implementation.

Vitamin D a fat-soluble steroid hormone signals through Vitamin D Receptors (VDRs) located throughout the ovaries, uterus, placenta, hypothalamus, and pituitary gland, influencing immune regulation and female reproductive physiology. This review of studies from 2013-2025 found consistent associations between low vitamin D status and various disorders in women of childbearing age. In Premenstrual Syndrome (PMS), deficiency correlates with higher symptom severity, and evidence shows that supplementation significantly reduces total PMS scores, particularly improving mood-related domains. For uterine pathologies such as fibroids, endometriosis, and adenomyosis, low vitamin D status is linked to increased risk and severity. Repletion trials suggest antifibrotic and analgesic benefits, although larger, more rigorously designed studies are still needed for definitive clinical guidelines. In Polycystic Ovary Syndrome (PCOS), low vitamin D links to adverse metabolic and hormonal profiles. Multiple randomized controlled trials (RCTs) confirm that correcting deficiency improves insulin resistance, lowers total testosterone and free-androgen index, raises sex-hormone-binding globulin (SHBG), and helps regularize menstrual cycles. Targeted supplementation is recommended, especially for insulin-resistant or obese phenotypes. During pregnancy, maternal deficiency is associated with adverse outcomes including pre-eclampsia, gestational diabetes, and pre-term birth risk. However, intervention trials have yielded inconsistent preventive results, often complicated because rising Vitamin D-Binding Protein (VDBP) may mask true vitamin D status. In Assisted Reproduction like In Vitro Fertilization (IVF), correcting deficiency early during pre-conception or early folliculogenesis appears beneficial. This early dosing enhances oocyte quality, promotes granulosa cell proliferation, and modulates local transcriptomes toward anti-inflammatory pathways. In contrast, single high-dose boluses administered shortly before embryo transfer show limited impact on outcomes. The overall evidence is limited by heterogeneous study designs, variable dosing, and reliance on total serum levels rather than bioavailable vitamin D. Future research should prioritize large, multicenter RCTs utilizing standardized daily/weekly dosing, stratifying by genetic and phenotypic factors, and measuring bioavailable vitamin D to establish reliable effects on patient-centered outcomes.

The 2025–2030 Dietary Guidelines introduce an important shift in public health nutrition, emphasizing minimally processed foods, higher protein intake, greater inclusion of full-fat dairy, and a food-based advice centered on “real food” consumption. While several of these recommendations align with accumulating evidence, particularly the discouragement of ultra-processed foods and added sugars, substantial concerns remain regarding their internal coherence, population-level applicability, risk of misinterpretation, as well as environmental footprint. This critical narrative review evaluates whether the scope, emphasis, and framing of the new guideline components are proportionate to the strength, consistency, and context of the underlying evidence. Using a novel framework that distinguishes between nutritional adequacy, optimization, and therapeutic application, we assess the scientific coherence of key recommendations. A structured literature search was conducted in PubMed, Scopus, and Web of Science focusing on systematic reviews and meta-analyses of randomized controlled trials and large prospective cohort studies relevant to the updated guidelines. Particular attention is given to protein and saturated fat intakes, carbohydrate restriction in chronic disease, and the balance between simplification and scientific precision. Overall, the new guidelines represent a positive shift toward food-based recommendations; however, clearer differentiation between population-level guidance and context-specific interventions is required to preserve scientific rigor, reduce misinterpretation, and enhance public health relevance.

Vitamin D deficiency is prevalent in type 2 diabetes mellitus (T2DM) and may influence metabolic control. The efficacy of supplementation remains contested. This systematic review aimed to evaluate the effect of vitamin D supplementation on primary glycemic outcomes (HbA1c, fasting blood glucose [FBG], HOMA-IR) and secondary metabolic parameters (lipid profile, blood pressure, anthropometrics) in adults with T2DM or prediabetes. This review was conducted according to Cochrane methodology and reported following PRISMA 2020 guidelines. Randomized controlled trials (RCTs) were identified via systematic searches of PubMed, Scopus, and Web of Science up to March 2025. Study selection, data extraction, and risk of bias assessment (using Cochrane RoB 2 tool) were performed in duplicate. A narrative synthesis was performed due to substantial heterogeneity. Thirty RCTs (n = 2627) were included. Studies varied in vitamin D dosage (1,000 to 600,000 IU), duration (8-52 wk), and participant baseline status. Overall, supplementation consistently increased serum 25(OH)D levels. For primary outcomes, significant reductions in HbA1c and FBG were reported in approximately half of the studies, particularly among participants with baseline vitamin D deficiency. Effects on HOMA-IR were mixed. Secondary outcomes (lipids, blood pressure, BMI) showed minimal or inconsistent changes. Vitamin D supplementation may improve glycemic control in individuals with T2DM who are vitamin D deficient, but appears ineffective in those with sufficient levels. It does not consistently improve other metabolic parameters. Targeted supplementation based on individual vitamin D status is recommended, rather than universal administration.

Vitamin D plays a pivotal role in immune regulation, metabolic balance, skeletal health, and gene expression. Growing evidence indicates that genetic and epigenetic factors contribute to interindividual differences in vitamin D status and physiological responses. This review summarizes current findings on the nutrigenomic determinants of vitamin D metabolism, with emphasis on genetic polymorphisms in vitamin D receptor (VDR), GC, CYP2R1, CYP27B1, and CYP24A1, as well as epigenetic mechanisms that modulate vitamin D related gene expression. Peer-reviewed original studies and review articles published between 2010 and 2025 were examined to highlight associations between genetic variation in the vitamin D pathway and susceptibility to cancer, autoimmune disorders, metabolic diseases, cardiovascular conditions, and neurodegenerative outcomes. Advances in omics technologies and epigenetic biomarker research have improved understanding the molecular pathways through which vitamin D acts across multiple body systems. Evidence from gene–environment interactions and genotype-specific supplementation responses highlights the conceptual relevance of precision nutrition, while underscoring substantial gaps in clinical validation. Collectively, current research suggests that genetic information may inform future personalized vitamin D strategies, although translation into clinical practice remains limited by inconsistent evidence and methodological heterogeneity.

Vitamin D has emerged as a modulatory factor in the pathogenesis and management of diabetes mellitus due to its influence on pancreatic β-cell function, immune regulation, and inflammatory pathways. This narrative review critically examines mechanistic and clinical evidence linking vitamin D status with type 1 diabetes (T1DM), type 2 diabetes (T2DM), and gestational diabetes (GDM). In T1DM, vitamin D’s immunomodulatory effects are thought to protect β-cells from autoimmune destruction; epidemiological studies associate vitamin D sufficiency with lower T1DM incidence and improved glycemic control, although causality remains under investigation. In T2DM, vitamin D deficiency is associated with worsened metabolic control and may contribute to disease development in at-risk individuals; however, it does not influence the initial onset of T2DM in patients who are already diagnosed. Intervention trials indicate that correcting the deficiency can modestly improve insulin sensitivity, β-cell function, and metabolic parameters. GDM has similarly been linked to hypovitaminosis D, with low maternal vitamin D levels associated with higher GDM risk and adverse perinatal outcomes; mechanistic insights suggest that adequate vitamin D supports glucose homeostasis in pregnancy, and emerging trials demonstrate improved insulin resistance with maternal vitamin D supplementation. Across these diabetes subtypes, maintaining sufficient vitamin D levels appears to confer metabolic benefits and may serve as an adjunct to current preventive and therapeutic strategies. However, definitive evidence from large-scale trials is required to establish optimal vitamin D supplementation protocols and confirm its efficacy in diabetes care.