Nutrients

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13 pages, 557 KB

Open AccessArticle

The Impact of Exogenous Vitamin D on Pituitary Effects of Metformin in Postmenopausal Women with Subclinical Hypothyroidism and Normal Vitamin D Status: A Pilot Study

by Robert Krysiak, Karolina Kowalcze, Johannes Ott, Simona Zaami, Giuseppe Gullo and Bogusław Okopień

Nutrients 2026, 18(5), 838; https://doi.org/10.3390/nu18050838 - 5 Mar 2026

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Abstract

Background/Objectives: Low vitamin D status was found to attenuate the impact of metformin on circulating levels of anterior pituitary hormones, but this inhibitory effect was absent in vitamin D-repleted subjects. No previous study investigated the interaction between metformin and exogenous vitamin D [...] Read more.

Background/Objectives: Low vitamin D status was found to attenuate the impact of metformin on circulating levels of anterior pituitary hormones, but this inhibitory effect was absent in vitamin D-repleted subjects. No previous study investigated the interaction between metformin and exogenous vitamin D at the pituitary levels in individuals with normal vitamin D status. Methods: Our pilot, single-center, prospective, matched-cohort study enrolled 59 postmenopausal women with subclinical hypothyroidism and 25-hydroxyvitamin D levels in the range between 75 and 150 nmol/L. For the following six months, all the participants were treated with either metformin/vitamin D combination therapy (group 1, n = 27) or metformin alone (group 2, n = 32). The outcomes of interest included 25-hydroxyvitamin D, fasting glucose, HOMA-IR, HbA_1c, TSH, FSH, LH, prolactin, ACTH, free thyroid hormones, estradiol and IGF-1. A parallel study investigated the impact of vitamin D monotherapy on the outcome measures in insulin-resistant women meeting the remaining inclusion criteria. Results: No differences in baseline biomarker values were observed between groups 1 and 2. Ninety-three percent of the patients completed the study. The increase in 25-hydroxyvitamin D levels was observed exclusively in group 1. Although glucose homeostasis markers and post-treatment levels of TSH and FSH were lower at the end of the study than at baseline in both groups, the effect of treatment was more pronounced in group 1 than in group 2. Metformin/vitamin D combination therapy, but not metformin alone, reduced LH and prolactin levels. In both groups, the TSH- and gonadotropin-lowering effects of metformin correlated with baseline levels of these pituitary hormones. Levels of ACTH, free thyroxine, free triiodothyronine, estradiol and IGF-1 remained stable throughout the study. The effects of vitamin D monotherapy were confined to an increase in plasma 25-hydroxyvitamin D concentrations and a modest enhancement in insulin sensitivity. Conclusions: Exogenous vitamin D potentiates the pituitary effects of metformin in postmenopausal women with subclinical hypothyroidism. Full article

(This article belongs to the Special Issue Vitamins and Human Health: 3rd Edition)

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17 pages, 298 KB

Open AccessArticle

Mediterranean Diet Adherence and Vitamin Intake Adequacy in Spanish University Students: Associations with Body Composition and Physical Activity

by Cristina Petisco-Rodríguez, Gema Barrientos-Vicho, Francisco Javier Alves-Vas and Ignacio Bartolomé Sánchez

Nutrients 2026, 18(4), 558; https://doi.org/10.3390/nu18040558 - 8 Feb 2026

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Abstract

Background/Objectives: This study examined the relationship between adherence to the Mediterranean diet (MD), dietary and vitamin intake, physical activity, and body composition in young adults. Methods: A total of 145 Spanish university students (34 women and 111 men) were included in this cross-sectional [...] Read more.

Background/Objectives: This study examined the relationship between adherence to the Mediterranean diet (MD), dietary and vitamin intake, physical activity, and body composition in young adults. Methods: A total of 145 Spanish university students (34 women and 111 men) were included in this cross-sectional study, with a mean body mass index (BMI) of 23 kg/m². MD adherence was assessed using the Mediterranean Diet Adherence Screener (MEDAS). Dietary intake was evaluated through a three-day food record, physical activity using the International Physical Activity Questionnaire (IPAQ), and body composition by bioelectrical impedance analysis. Results: Overall adherence to the MD was moderate. Participants with high MD adherence showed significantly lower body weight (p < 0.05; d = 0.4), BMI (p < 0.01; d = 0.52), fat mass (p < 0.05; d = 0.44), and fat mass percentage (p < 0.05; d = 0.38) compared with those with low adherence. Energy (p < 0.05; d = 0.41), protein (p < 0.05; d = 0.65), and carbohydrate (p < 0.05; d = 0.37) intake per kilogram of body weight were higher in the high-adherence group. Fiber intake was greater (p < 0.001; d = 0.82) among those with higher MD adherence. Adherence to the MD was also associated with higher intakes of vitamins C (p < 0.05; d = 0.39) and E (p < 0.05; d = 0.62), retinol equivalents (p < 0.05; d = 0.28), and carotenoids (p < 0.001; d = 0.79). MD adherence was inversely correlated with body weight (r_s = −0.32; p < 0.01; r = 0.46) and BMI (r_s = −0.34; p < 0.01; r = 0.32). Fiber intake showed positive correlations with several water-soluble vitamins, particularly folate (HAG: r_s = 0.68; p < 0.001; r = 0.81 and LAG: r_s = 0.61; p < 0.001; r = 0.69). Conclusions: In conclusion, higher adherence to the MD among university students was associated with healthier body composition and improved vitamin intake adequacy. These findings support the promotion of the MD as an effective nutritional strategy to enhance micronutrient intake and overall diet quality in young adults. Full article

(This article belongs to the Special Issue Vitamins and Human Health: 3rd Edition)

11 pages, 885 KB

Open AccessArticle

High Prevalence and Clinical Associations of Vitamin D Deficiency in Inflammatory Bowel Disease: Evidence from a Tertiary Center Cohort

by Theodora Kafentzi, Ploutarchos Pastras, Ioanna Aggeletopoulou, Efthymios P. Tsounis, Georgios Geramoutsos, Nikitas Kimiskidis, Maria Bali, Konstantinos Thomopoulos, Georgia Diamantopoulou, Georgios Theocharis and Christos Triantos

Nutrients 2025, 17(23), 3698; https://doi.org/10.3390/nu17233698 - 25 Nov 2025

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Abstract

Background/Objectives: Vitamin D in its active form, 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], plays a critical role in immune regulation, gut barrier function, and systemic inflammation. Its deficiency is frequent in Inflammatory Bowel Disease (IBD), but the clinical implications remain uncertain. [...] Read more.

Background/Objectives: Vitamin D in its active form, 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], plays a critical role in immune regulation, gut barrier function, and systemic inflammation. Its deficiency is frequent in Inflammatory Bowel Disease (IBD), but the clinical implications remain uncertain. The aim of the study is to assess the prevalence of vitamin D deficiency in a well-characterized IBD cohort in Western Greece, and explore its associations with clinical features, laboratory biomarkers, and treatment intensity. Methods: In this cross-sectional study, 184 consecutive, well-characterized IBD outpatients followed at a tertiary referral center in Western Greece underwent clinical evaluation and laboratory testing between January 2023 and December 2024. Vitamin D is determined by measuring 25-hydroxyvitamin D [25(OH)D], which reflects the body’s vitamin D stores due to its longer half-life compared with the biologically active form. Deficiency was defined as serum 25(OH)D < 20 ng/mL. Associations with disease type, clinical and laboratory biomarkers, severity indices, and treatment were analyzed using multivariate logistic regression. Results: Vitamin D deficiency was identified in 67 patients (36.4%). Although unrelated to disease type, hospitalization, surgery, or disease activity indices, deficiency correlated with systemic inflammation, nutrition/metabolic markers, and treatment intensity. More specifically, vitamin D-deficient patients exhibited higher platelet counts (p = 0.005) and erythrocyte sedimentation rate (ESR) (p = 0.014), lower hemoglobin (p = 0.005), albumin (p = 0.011), and serum glutamic-oxaloacetic transaminase (SGOT) (p = 0.009) levels and more frequent use of biologic therapy (p = 0.009). In multivariate analysis, vitamin D deficiency remained independently associated with biologic therapy (aOR = 0.374; 95% CI: 0.148–0.946), platelet count (aOR = 0.996, 95% CI: 0.992–0.999), and SGOT (aOR = 1.05, 95% CI: 1.00–1.10), indicating consistent links between vitamin D deficiency and treatment intensity, systemic inflammation, and nutritional or metabolic status. Conclusions: Vitamin D deficiency is common among IBD patients and independently associates with systemic inflammation, metabolic impairment, and intensified treatment requirement, supporting its potential role as a marker of disease burden. Full article

(This article belongs to the Special Issue Vitamins and Human Health: 3rd Edition)

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10 pages, 699 KB

Open AccessArticle

Association of Vitamins and Minerals with Type 1 Diabetes Risk: A Mendelian Randomization Study

by Lucia Shi, Wiame Belbellaj and Despoina Manousaki

Nutrients 2025, 17(20), 3297; https://doi.org/10.3390/nu17203297 - 20 Oct 2025

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Abstract

Background/Objectives: Previous studies suggest that nutrient deficiencies can alter immune responses in animals. However, the impact of micronutrients on autoimmune diseases like type 1 diabetes (T1D) in humans remains unclear since the described associations are based on observational data and they cannot establish [...] Read more.

Background/Objectives: Previous studies suggest that nutrient deficiencies can alter immune responses in animals. However, the impact of micronutrients on autoimmune diseases like type 1 diabetes (T1D) in humans remains unclear since the described associations are based on observational data and they cannot establish causality. This study aims to examine the causal relationship between various micronutrients and T1D using Mendelian randomization (MR). Methods: We performed a two-sample MR analysis using genetic variants from genome-wide association studies (GWASs) of 17 micronutrients as instrumental variables (IVs). We analyzed T1D GWAS datasets of European (18,942 cases/520,580controls), multi-ancestry (25,717 cases/583,311 controls), Latin American/Hispanic (2295 cases/55,134 controls), African American/Afro-Caribbean (6451 cases/109,410 controls), and East Asian (1219 cases/132,032 controls) ancestries. We applied the inverse variance weighted (IVW) method in our main analysis, and additional MR estimators (MR-Egger, weighted median, weighted mode, MR-PRESSO) to address pleiotropy, and the Steiger test to test directionality in sensitivity analyses. Results: Following Bonferroni correction (p < 0.05/17), we found positive association between potassium levels and T1D risk (OR = 1.098, 95% CI [1.075, 1.122] p = 5.5 × 10⁻¹⁸) in the multi-ancestry analysis. Zinc, vitamin B12, retinol, and alpha tocopherol showed nominal associations. Vitamin C, D, K1, B6, beta- and gamma-tocopherol, magnesium, iron, copper, selenium, carotene, and folate showed no significant effects on T1D risk. For the multi-ancestry analysis, we had sufficient power to detect ORs for T1D larger than 1.065. Conclusions: Higher serum potassium levels were associated with increased T1D risk in our MR study, though supporting observational evidence is currently limited. Other micronutrients are unlikely to have large effects on T1D. Full article

(This article belongs to the Special Issue Vitamins and Human Health: 3rd Edition)

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12 pages, 1044 KB

Open AccessArticle

Serum 25-Hydroxyvitamin D Is Decreased with Metabolic Syndrome Following Anterior Cruciate Ligament Reconstruction

by Sonu Bae, Anthony Mantor, Hayden Price, Christopher C. Kaeding, Robert A. Magnussen, David C. Flanigan and Tyler Barker

Nutrients 2025, 17(15), 2410; https://doi.org/10.3390/nu17152410 - 24 Jul 2025

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Abstract

Background/Objectives: Serum 25-hydroxyvitamin D (25(OH)D) concentrations are decreased with metabolic syndrome (MetSy), and low serum 25(OH)D concentrations are associated with poor outcomes following anterior cruciate ligament (ACL) reconstruction (ACLR). It is unknown whether serum 25(OH)D concentrations are decreased in patients with MetSy [...] Read more.

Background/Objectives: Serum 25-hydroxyvitamin D (25(OH)D) concentrations are decreased with metabolic syndrome (MetSy), and low serum 25(OH)D concentrations are associated with poor outcomes following anterior cruciate ligament (ACL) reconstruction (ACLR). It is unknown whether serum 25(OH)D concentrations are decreased in patients with MetSy following ACLR. The purpose of this study was to investigate whether serum 25(OH)D concentrations are decreased with MetSy following ACLR. Methods: This retrospective case–control study consisted of patients (≥18 years) who underwent ACLR. MetSy was defined as meeting any three of the five criteria (cases): (1) body mass index ≥ 30 kg/m², (2) triglycerides ≥ 150 mg/dL, (3) HDL < 40 mg/dL in men and <50 mg/dL in women, (4) systolic blood pressure ≥ 130 mmHg or diastolic blood pressure ≥ 85 mmHg, or (5) estimated (from hemoglobin A1c% [HbA1c]) fasting glucose ≥ 100 mg/dL. Participants without MetSy (meeting <3 criteria) served as controls. The first blood lipid, HbA1c, and 25(OH)D assessed ≥90 d after ACLR were included in this study. Results: The final analysis consisted of 219 patients (cases (with MetSy), n = 84; controls (without MetSy), n = 135). Serum 25(OH)D was significantly (p < 0.01) decreased (15.8%) in cases (mean [SD]; 25.1 [11.3] ng/mL) compared to controls (29.8 [14.8] ng/mL). An increasing number of MetSy components was associated with a decreased prevalence of vitamin D sufficiency (p < 0.01). Conclusions: We conclude that serum 25(OH)D concentrations are significantly lower with MetSy. These preliminary findings could provide justification for assessing serum 25(OH)D following ACLR in patients with MetSy and assist with risk stratification. Full article

(This article belongs to the Special Issue Vitamins and Human Health: 3rd Edition)

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24 pages, 657 KB

Open AccessArticle

Sexual Functioning and Depressive Symptoms in Levothyroxine-Treated Women with Postpartum Thyroiditis and Different Vitamin D Status

by Karolina Kowalcze, Joanna Kula-Gradzik, Anna Błaszczyk and Robert Krysiak

Nutrients 2025, 17(13), 2091; https://doi.org/10.3390/nu17132091 - 24 Jun 2025

Cited by 3 | Viewed by 3144

Abstract

Background/Objectives: Hypothyroidism and thyroid autoimmunity have a negative effect on women’s sexual health, which is only partially reversed by thyroid hormone substitution. Sexual functioning in thyroid disorders after delivery has been poorly researched. The aim of our study was to compare the [...] Read more.

Background/Objectives: Hypothyroidism and thyroid autoimmunity have a negative effect on women’s sexual health, which is only partially reversed by thyroid hormone substitution. Sexual functioning in thyroid disorders after delivery has been poorly researched. The aim of our study was to compare the effect of levothyroxine on sexual response and depressive symptoms in women with postpartum thyroiditis (PPT) and different vitamin D status. Methods: The study population consisted of three matched groups of women with the hypothyroid phase of PPT: two groups with subclinical and one with overt thyroid hypofunction. Each group included similar numbers of women with normal and low vitamin D status. For the following six months, one group of women with subclinical hypothyroidism and all women with overt thyroid hypofunction received levothyroxine. At the beginning and at the end of the study, all participants completed questionnaires evaluating female sexual function (FSFI) and depressive symptoms (BMI-II). The remaining outcomes of interest included thyroid antibody titers, and the serum levels of 25-hydroxyvitamin D, TSH, free thyroid hormones, sex hormones, and prolactin. Results: Before levothyroxine substitution, women with overt and subclinical disease differed in the total FSFI score, all domain scores, and the overall BDI-II score. Within each study group, domain scores for desire were greater in women with vitamin D sufficiency than in those with vitamin D deficiency/insufficiency. Testosterone and estradiol levels were lower in women with overt than in women with subclinical hypothyroidism, while the opposite relationship was found for prolactin. Levothyroxine treatment improved all domains of female sexual function and reduced the total BDI-II score in both patients with overt and subclinical hypothyroidism and normal vitamin D status. In women with vitamin D deficiency/insufficiency, the impact of this agent was limited to arousal, lubrication, and sexual satisfaction. Levothyroxine replacement reduced thyroid antibody titers only in women with normal vitamin D status. The impact on testosterone was limited to women with normal vitamin D status, and was more pronounced in women with overt than subclinical disease. The effect on estradiol and prolactin, observed only in overt disease, was unrelated to vitamin D status. The increase in sexual functioning correlated with the following: 25-hydroxyvitamin D levels (in vitamin D-deficient/insufficient women); the impact on thyroid peroxidase antibodies, free triiodothyronine and testosterone (for desire and arousal); and the changes in the overall BDI-II score. Five years later, the quality of life was better in vitamin D-sufficient women receiving levothyroxine in the postpartum period. Conclusions: Low vitamin D status attenuates the impact of levothyroxine on female sexual function and depressive symptoms in women with the hypothyroid phase of PPT. Full article

(This article belongs to the Special Issue Vitamins and Human Health: 3rd Edition)

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17 pages, 1524 KB

Open AccessArticle

Vitamin Status and Risk of Age-Related Diseases Among Adult Residents of the Pearl River Delta Region

by Yongze Zhao, Siqian Zheng, Bohan Wang, Wenhui Xiao, Ping He and Ying Bian

Nutrients 2025, 17(10), 1637; https://doi.org/10.3390/nu17101637 - 10 May 2025

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Abstract

Background: The Pearl River Delta (PRD) region in Guangdong, China, is urbanized and economically significant. Rapid development has shaped diverse dietary habits. In this densely populated area, there is an urgent need to assess vitamin status and its impact on age-related diseases. [...] Read more.

Background: The Pearl River Delta (PRD) region in Guangdong, China, is urbanized and economically significant. Rapid development has shaped diverse dietary habits. In this densely populated area, there is an urgent need to assess vitamin status and its impact on age-related diseases. Methods: A total of 2646 participants (age: 50.92 ± 9.30 years; male: 64.06%) were recruited from the Pearl River Delta (PRD) region. Participants were included from 1 December 2020 to 30 November 2021. Three restricted cubic spline logistic models, interaction terms, and mediated effects analyses were used to assess the association between vitamin A, B, E, B₁, B₂, B₃, B₅, B₆, and B₉ between five age-related diseases: cerebrovascular disease (CVD), coronary heart disease (CHD), hypertension (HTN), dyslipidemia (DYS), and type 2 diabetes mellitus (T2DM). Results: Blood concentrations of nine vitamins showed a right-skewed distribution. Significant correlations were found between vitamin levels and age-related diseases across nine groups (p < 0.05). A J-shaped relationship was observed between vitamin levels and the risk of age-related diseases, except for the Vitamin A-HTN/T2DM, which showed Maximum Effective Concentration (MEC). Specific thresholds included: Vitamin A: 1080 ng/mL (DYS); Vitamin B₁: 77 ng/mL (CVD), 75.5 ng/mL (HTN); Vitamin B₅: 900 ng/mL (CVD), 600 ng/mL (HTN), 690 ng/mL (DYS); Vitamin B₆: 82 ng/mL (CVD). The protective effect of vitamins against age-related diseases decreased with age, and higher levels of vitamins A and B₁ correlated with increased hypertension risk in older adults (P_interaction < 0.01). Low Body Resilience Index (BRI) and physical activity mediated the protective effects of vitamins A and B₅ on HTN and DYS, while no mediating effects were found for smoking and alcohol consumption. Conclusions: The effectiveness of multivitamin supplementation in preventing cardiovascular, cerebrovascular, and metabolic diseases may be limited in healthy aging populations. Health professionals should consider patients’ physiological conditions and blood vitamin levels to avoid overdose. More interventional studies are needed to establish causal relationships. Full article

(This article belongs to the Special Issue Vitamins and Human Health: 3rd Edition)

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Review

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44 pages, 1154 KB

Open AccessReview

Vitamin D in Cardiovascular Medicine: From Molecular Mechanisms to Clinical Translation

by Fahimeh Varzideh, Pasquale Mone, Urna Kansakar and Gaetano Santulli

Nutrients 2026, 18(3), 499; https://doi.org/10.3390/nu18030499 - 2 Feb 2026

Cited by 1 | Viewed by 1754

Abstract

Vitamin D, a fat-soluble secosteroid traditionally recognized for skeletal health, exerts pleiotropic effects on cardiovascular physiology and disease. Circulating 25-hydroxyvitamin D [25(OH)D], the principal biomarker of vitamin D status, is frequently suboptimal worldwide, particularly in older adults, individuals with darker skin pigmentation, and [...] Read more.

Vitamin D, a fat-soluble secosteroid traditionally recognized for skeletal health, exerts pleiotropic effects on cardiovascular physiology and disease. Circulating 25-hydroxyvitamin D [25(OH)D], the principal biomarker of vitamin D status, is frequently suboptimal worldwide, particularly in older adults, individuals with darker skin pigmentation, and populations at higher latitudes. Observational studies consistently associate low 25(OH)D concentrations with increased risk of hypertension, atherosclerosis, myocardial infarction, heart failure, arrhythmias, stroke, and cardiovascular mortality. Mechanistic investigations have revealed that vitamin D modulates cardiomyocyte calcium handling, endothelial function, vascular smooth muscle proliferation, inflammation, oxidative stress, and renin–angiotensin–aldosterone system activity, establishing biologically plausible links to cardiovascular outcomes. Despite these associations, large randomized trials of vitamin D supplementation have failed to demonstrate reductions in major cardiovascular events, likely due to heterogeneity in baseline status, dosing regimens, intervention timing, genetic variability, and underlying comorbidities. Vitamin D may function more effectively as a biomarker of cardiovascular risk rather than a universal therapeutic agent, with deficiency reflecting systemic vulnerability rather than acting as a dominant causal factor. Emerging evidence supports precision approaches targeting individuals with severe deficiency, high renin activity, early endothelial dysfunction, or specific genetic profiles, potentially in combination with lifestyle or pharmacologic interventions. Future research should focus on defining optimal dosing strategies, intervention timing, and mechanistic biomarkers to identify subpopulations most likely to benefit, integrating vitamin D therapy into multifaceted cardiovascular prevention frameworks. This systematic review synthesizes molecular, observational, and clinical trial evidence, critically evaluating the current understanding of vitamin D in cardiovascular medicine and highlighting opportunities for targeted, personalized interventions. Vitamin D represents a complex, context-dependent modulator of cardiovascular health, offering both prognostic insight and potential therapeutic value when appropriately applied. Full article

(This article belongs to the Special Issue Vitamins and Human Health: 3rd Edition)

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17 pages, 2213 KB

Open AccessReview

The Differential Effects of Vitamin K Across Glycaemic Outcomes in Prediabetes and Type 2 Diabetes Mellitus

by Syeda Ruwaida Ahmed, Kabelo Mokgalaboni and Wendy N. Phoswa

Nutrients 2026, 18(2), 269; https://doi.org/10.3390/nu18020269 - 14 Jan 2026

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Background: Vitamin K has emerged as a promising regulator of glucose metabolism in preclinical studies. There is, however, scant evidence to support this promising potential in a clinical setting. Aim: The aim of this study was to confirm the effects of vitamin K [...] Read more.

Background: Vitamin K has emerged as a promising regulator of glucose metabolism in preclinical studies. There is, however, scant evidence to support this promising potential in a clinical setting. Aim: The aim of this study was to confirm the effects of vitamin K supplementation on glycaemic parameters such as fasting blood glucose (FBG), fasting insulin (FI), glycated haemoglobin (HbA1c), insulin resistance (HOMA-IR), and homeostatic model of beta cell function (HOMA-β) across randomised controlled trials (RCTs). Materials and Methods: This meta-analysis used evidence from PubMed, Scopus, and manual screening. Only RCTs were considered for this meta-analysis of interventional studies. The Meta online tool was used to analyse data, with the results reported as either the mean or the standardised mean difference (SMD), alongside 95% confidence intervals (CI). Results: Only eight RCTs were found relevant and analysed; the age of those in the vitamin K group was 50.58 ± 6.91 years, and in the control group, it was 48.19 ± 5.41. The evidence showed a significant reduction in FBG, SMD = −0.22 (−0.39 to −0.05), HbA1c, MD = −1.00%, 95% CI (−1.92 to −0.07), and HOMA-IR, MD = −0.63, 95% CI (−1.20 to −0.06). However, no effect was observed on insulin (SMD = −0.39, 95% CI: −0.91 to 0.13, p = 0.15) and HOMA-β (MD = 6.56, 95% CI (−3.89 to 17.01), p = 0.2184. Low doses of vitamin K2 and vitamin K1 were associated with reduced HbA1c and HOMA-IR, respectively. An intervention of less than 12 weeks was associated with reduced HOMA-IR. Conclusions: This study showed a significant decrease in FBG, HbA1c, and HOMA-IR without affecting insulin or HOMA-β. Nevertheless, the limited number of trials with moderate quality warrants larger, longer-term RCTs with rigorous methodology and direct comparisons of vitamin K isoforms to better assess therapeutic potential. Full article

(This article belongs to the Special Issue Vitamins and Human Health: 3rd Edition)

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33 pages, 1265 KB

Open AccessReview

Vitamin Supplementation in Sports: A Decade of Evidence-Based Insights

by Magdalena Wiacek, Emilia Nowak, Piotr Lipka, Remigiusz Denda and Igor Z. Zubrzycki

Nutrients 2026, 18(2), 213; https://doi.org/10.3390/nu18020213 - 9 Jan 2026

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Background: Vitamins are micronutrients involved in multiple physiological processes critical for athletic performance. Because athletes are often exposed to increased oxidative stress, higher metabolic turnover, and greater nutritional demands, which can potentially lead to deficiencies in vitamins, understanding vitamin supplementation as a [...] Read more.

Background: Vitamins are micronutrients involved in multiple physiological processes critical for athletic performance. Because athletes are often exposed to increased oxidative stress, higher metabolic turnover, and greater nutritional demands, which can potentially lead to deficiencies in vitamins, understanding vitamin supplementation as a function of sport discipline is of fundamental importance. Methods: This narrative review synthesizes research findings from the past decade, supplemented with earlier studies where necessary, focusing on vitamins A, C, D, E, and the B-complex vitamins. Peer-reviewed literature was evaluated for evidence on the prevalence of deficiencies in athletes, physiological mechanisms, supplementation strategies, and their effects on performance, injury prevention, and recovery. Results: Vitamin D deficiency is highly prevalent among athletes, particularly in indoor sports and during the winter months. Supplementation has been shown to improve musculoskeletal health and potentially reduce injury risk. The antioxidant vitamins C and E can attenuate exercise-induced oxidative stress and muscle damage; however, excessive intake may impair adaptive responses such as mitochondrial biogenesis and protein synthesis. Vitamin A contributes to immune modulation, metabolic regulation, and mitochondrial function, while B-complex vitamins support energy metabolism and red blood cell synthesis. Conclusions: Vitamin supplementation in athletes should be individualized, targeting confirmed deficiencies and tailored to sport-specific demands, age, sex, and training intensity. Dietary optimization should remain the primary strategy, with supplementation serving as an adjunct when intake is insufficient. Further high-quality, sport-specific, and long-term studies are needed to establish clear dosing guidelines and to assess the balance between performance benefits and potential risks associated with over-supplementation. Full article

(This article belongs to the Special Issue Vitamins and Human Health: 3rd Edition)

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21 pages, 5768 KB

Open AccessSystematic Review

Complex Effects of B-Vitamin Combinations on Cardiovascular Diseases: A Systematic Review and Meta-Analysis of Randomized Controlled Trials over Three Decades

by Ruodi Ren, Andrew Yang, Allison Chow, Kunkun Wang, Shan Wang, Christopher Leo, Yun Lu and Mengyan Li

Nutrients 2026, 18(5), 842; https://doi.org/10.3390/nu18050842 - 5 Mar 2026

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Background and Purpose: The effects of B-vitamin combinations on the prevention of cardiovascular diseases, such as myocardial infarction (MI) and stroke, remain controversial. We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) over three decades to evaluate the association between [...] Read more.

Background and Purpose: The effects of B-vitamin combinations on the prevention of cardiovascular diseases, such as myocardial infarction (MI) and stroke, remain controversial. We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) over three decades to evaluate the association between B-vitamin combinations and mortality and arterial thrombotic outcomes. Methods: PubMed, Embase, Web of Science, and the Cochrane Library were systematically searched for RCTs with minimal duration over 24 months published between January 1996 and November 2025. Two reviewers independently screened studies, extracted data, and assessed risk of bias using the Cochrane Risk of Bias 2.0 tool. Random-effects models were used in this meta-analysis to calculate pooled risk ratios (RRs) and 95% confidence intervals (CIs). Results: Thirteen randomized trials enrolling 68,363 participants across both primary and secondary prevention populations were included. B-vitamin combinations were associated with a nonsignificant reduction in stroke and 3-point major adverse cardiovascular events (MACE) (stroke: RR 0.91, 95% CI 0.81–1.04; MACE: RR 0.93, 95% CI 0.86–1.01). No significant effects were observed for all-cause mortality (RR 1.01, 95% CI 0.96–1.06), cardiovascular mortality (RR 0.97, 95% CI 0.88–1.07), or MI (RR 0.97, 95% CI 0.91–1.03). In primary prevention populations, B-vitamin combinations were associated with significant reductions in stroke (RR 0.79, 95% CI 0.68–0.93) and MACE (RR 0.80, 95% CI 0.69–0.92). A modest reduction in MACE was also observed in secondary prevention populations (RR 0.91, 95% CI 0.83–0.99). Between-study heterogeneity was minimal to low for ischemic outcomes, supporting the robustness of these estimates, whereas substantial heterogeneity was observed for mortality outcomes in secondary prevention populations. Conclusions: The evidence is limited by heterogeneity in trial populations, vitamin formulations and doses, and outcome definitions, with substantial between-study inconsistency for mortality outcomes and imprecision in subgroup estimates derived from a small number of contributing trials. Overall, B-vitamin combinations do not confer consistent benefit for major cardiovascular outcomes but may reduce stroke and MACE in selected primary prevention populations, suggesting that baseline cardiovascular risk and regional folic acid fortification modify treatment effects and should guide future trial design and clinical use. Full article

(This article belongs to the Special Issue Vitamins and Human Health: 3rd Edition)

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