Causal association between low vitamin D and polycystic ovary syndrome: a bidirectional mendelian randomization study.

BACKGROUND: Recent studies have revealed the correlation between serum vitamin D (VD) level and polycystic ovary syndrome (PCOS), but the causality and specific mechanisms remain uncertain. OBJECTIVE: We aimed to investigate the cause-effect relationship between serum VD and PCOS, and the role of testosterone in the related pathological mechanisms. METHODS: We assessed the causality between serum VD and PCOS by using genome-wide association studies (GWAS) data in a bidirectional two-sample Mendelian randomization (TS-MR) analysis. Subsequently, a MR mediation analysis was conducted to examine the mediating action of testosterone in the causality between serum VD and PCOS. Ultimately, we integrated GWAS data with cis-expression quantitative loci (cis-eQTLs) data for gene annotation, and used the potentially related genes for functional enrichment analysis to assess the involvement of testosterone and the potential mechanisms. RESULTS: TS-MR analysis showed that individuals with lower level of serum VD were more likely to develop PCOS (OR = 0.750, 95% CI: 0.587-0.959, P = 0.022). MR mediation analysis uncovered indirect causal effect of serum VD level on the risk of PCOS via testosterone (OR = 0.983, 95% CI: 0.968-0.998, P = 0.025). Functional enrichment analysis showed that several pathways may be involved in the VD-testosterone-PCOS axis, such as steroid hormone biosynthesis and autophagy process. CONCLUSION: Our findings suggest that genetically predicted lower serum VD level may cause a higher risk of developing PCOS, which may be mediated by increased testosterone production.

Vitamin D, Alzheimer's disease and related dementia.

Vitamin D has been proposed as a potential strategy to mitigate age-related cognitive decline and dementia, including Alzheimer's dementia, the predominant type of dementia. Rodent studies have provided insight into the potential mechanisms underlying the role of vitamin D in Alzheimer's disease and dementia. However, inconsistencies with respect to age, sex, and genetic background of the rodent models used poses some limitations regarding scientific rigor and translation. Several human observational studies have evaluated the association of vitamin D status with cognitive decline and dementia, and the results are conflicting. Randomized clinical trials of vitamin D supplementation have included cognitive outcomes. However, most of the available trials have not been designed specifically to test the effect of vitamin D on age-related cognitive decline and dementia, so it remains questionable how much additional vitamin D will improve cognitive performance. Here we evaluate the strengths and limitations of the available evidence regarding the role of vitamin D in AD, cognitive decline, dementia.

Vitamin D and bone health: What vitamin D can and cannot do.

Historically vitamin D deficiency had devastating consequences for children causing rickets resulting in severe bone deformities often leading to death. The mystery of the cause of rickets finally came to light when it was observed that cod liver oil and sunlight could prevent and cure rickets. The first vitamin D to be discovered was vitamin D2 from ergosterol in ultraviolet irradiated yeast. Vitamin D3 was discovered from UV exposure to the skin. Investigations revealed the two major functions of vitamin D were to increase intestinal calcium and phosphate absorption and mobilize calcium from the skeleton to maintain calcium and phosphorus homeostasis. Later studies demonstrated that vitamin D does not have an active role in bone mineralization. Vitamin D deficiency results in secondary hyperparathyroidism increasing bone resorption. As a result, this decreases bone mineral content and compromises the architectural integrity increasing risk for fracture. Vitamin D deficiency has also been shown to enhance aging of the bone causing cracks and enhancing bone fractures. Vitamin D deficiency also causes osteomalacia. Therefore, vitamin D sufficiency is extremely important to maximize bone health throughout life. It helps to prevent bone loss, but it cannot restore bone loss due to increased bone resorption that can occur under a variety of circumstances including menopause. The Endocrine Society Guidelines recommends for all ages that adequate vitamin D obtained from the sun, foods and supplements is necessary in order to maintain a circulating concentration of 25-hydroxyvitamin D of at least 30 ng/mL for maximum bone health.

Vitamin D and celiac disease.

Celiac disease (CD) is an immune-mediated condition affecting the small intestine. Its reported global prevalence falls within the range of 0.7% to 1.4%. Notably, historically, higher rates, reaching 1% in Western Ireland, have been documented. Recent research has even revealed prevalence rates as elevated as 2% in northern Europe. These findings underscore the urgency for swift and cost-effective diagnosis, especially in individuals identified through screening efforts. At present, the diagnosis of CD relies on a multifaceted approach involving positive serological markers such as IgA anti-tissue transglutaminase (anti-TTG) and anti-endomysial antibodies (anti-EMA). These serological findings are assessed in conjunction with classical histological alterations, as outlined in the Marsh classification. CD is an inflammatory condition triggered by the consumption of gluten, resulting from intricate interactions between genetic, immunological, and environmental factors. CD is linked to malabsorption, leading to nutritional deficiencies. Individuals with CD are required to adhere to a gluten-free diet, which itself can lead to nutrient deficiencies. One such deficiency includes vitamin D, and there is substantial experimental evidence supporting the notion of a bidirectional relationship between CD and vitamin D status. A low level of vitamin D has a detrimental impact on the clinical course of the disease. Here we summarize the key characteristics of CD and explore the prominent roles of vitamin D in individuals with CD.

Vitamin D and cardiovascular diseases.

Vitamin D has an established role in calcium homeostasis but its deficiency is emerging also as a new risk factor for cardiovascular disease (CVD). In particular, several epidemiological and clinical studies have reported a close association between low vitamin D levels and several cardiovascular risk factors and major CVDs, such as coronary artery disease, heart failure, and cardiac arrhythmias. In all these clinical settings, vitamin D deficiency seems to predispose to increased morbidity, mortality, and recurrent cardiovascular events. Despite this growing evidence, interventional trials with supplementation of vitamin D in patients at risk of or with established CVD are still controversial. In this chapter, we summarize the currently available evidence on the links between vitamin D deficiency and major cardiovascular risk factors and CVD, in terms of both clinical relevance and potential therapeutic implications.

Vitamin D and obesity.

An inverse association between vitamin D status and obesity has been reported across diverse populations and age groups in humans. In animal model of diet-induced obesity, dysregulation of vitamin D metabolism has been observed. However, the causal relationship between vitamin D status and obesity is not conclusive. Several explanations, such as volumetric dilution, sequestration of vitamin D into adipose tissue, and limited sunlight exposure, have been suggested as the underlying mechanisms linking poor vitamin D status and obesity. Vitamin D can modulate adipose tissue biology, spanning from adipocyte differentiation to adipocyte apoptosis and energy metabolism, indicating its potential impact on adiposity. In this chapter, we will review the prevalence of vitamin D deficiency and determinants of vitamin D deficiency among different populations, as well as changes in vitamin D metabolism associated with obesity. Additionally, we will review vitamin D's regulation of adipogenesis and lipogenesis at the cellular level in order to gain a deeper understanding of the underlying mechanisms linking vitamin D levels and obesity.

Surgical Considerations for Osteoporosis, Osteopenia, and Vitamin D Deficiency in Upper Extremity Surgery.

Fragility fractures as a result of osteoporosis, osteopenia, or vitamin D deficiency are some of the most common injuries encountered in orthopedics and require careful consideration when determining the appropriate management and treatment options. A thorough perioperative evaluation can identify causes of low bone mineral density allowing for initiation of appropriate therapy. Surgical treatment of these fractures can be difficult, and techniques should be employed to ensure stable fixation. It is important to understand the potential pitfalls associated with treatment of fragility fractures to prevent avoidable complications. Postoperative management is key to preventing future injuries in this unique patient population.

Considerations Regarding Vitamin D in Foot and Ankle Treatment and Surgery.

Although the impact that vitamin D has on bone healing is uncertain in foot and ankle (F&A) surgery, there is support for vitamin D supplementation (2000 IU/day) with calcium (1 g/day) to promote bone healing. Although orthopedic F&A surgeons are frequently the first provider to detect the harbingers of osteoporosis by the occurrence of fragility fractures, this should trigger referral to the appropriate specialist for assessment and treatment. There is circumstantial evidence suggesting a role of hypovitaminosis D in bone marrow edema syndrome and possibly osteochondritis dissecans. There should be a low threshold for assessing vitamin D levels in such patients.

Frequency of vitamin D deficiency in children with iron deficiency anaemia and factors associated with vitamin D deficiency.

Objective: To evaluate vitamin D deficiency in children with iron-deficiency anaemia, and to identify the risk factors for such deficiency. METHODS: The cross-sectional study was conducted at the Children's Hospital, Pakistan Institute of Medical Sciences, Islamabad, Pakistan, from October 2021 to March 2022, and comprised children aged 1-5 years who had been diagnosed with iron-deficiency anaemia. Quantitative variables, like age, height, weight, gender, socioeconomic status and sibling status, were controlled by stratification. Data was compared to assess the risk factors of vitamin D deficiency among the subjects. Data was analysed using SPSS 22. RESULTS: Of the 236 children with iron-deficiency anaemia, 159(67.5%) also had vitamin D deficiency; 95(59%) girls and 65(41%) boys. Overall, 104(65.4%) subjects were aged 4-5 years and 55(34.6%) were aged 1-3 years. Vitamin D deficiency had significant association with female gender, older age, height and weight <5th centiles, educated parents, low to middle socioeconomic status, urban residence and higher number of siblings (p<0.05). CONCLUSIONS: The prevalence of vitamin D deficiency among children with iron-deficiency anaemia was found to be high.

Vitamin D and Menopause.

Menopause is the transition period in female life cycle. Resultant hormonal changes lead to adverse health effects. Women may seek treatment due to significant impairment in quality of life. Vitamin D deficiency is a globally prevalent problem. Vitamin D deficiency in menopausal women may aggravate the adverse health risks associated with menopause. In this article, the authors discuss endocrinology and clinical features of menopause, Vitamin D and its links with menopause, and the potential role of Vitamin D supplementation to combat detrimental multi-organ system effects of menopause.

Vitamin D and Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD): Novel Mechanistic Insights.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is an increasingly prevalent condition characterized by abnormal fat accumulation in the liver, often associated with metabolic disorders. Emerging evidence suggests a potential link between vitamin D deficiency and the development and progression of MASLD. The current review provides a concise overview of recent studies uncovering novel mechanistic insights into the interplay between vitamin D and MASLD. Several epidemiological studies have highlighted a significant association between low vitamin D levels and an increased risk of MASLD. Vitamin D, traditionally known for its role in bone health, has now been recognized as a key player in various physiological processes, including immune regulation and inflammation. Experimental studies using animal models have demonstrated that vitamin D deficiency exacerbates liver steatosis and inflammation, suggesting a potential protective role against MASLD. Mechanistically, vitamin D appears to modulate MASLD through multiple pathways. Firstly, the vitamin D receptor (VDR) is abundantly expressed in liver cells, indicating a direct regulatory role in hepatic function. Activation of the VDR has been shown to suppress hepatic lipid accumulation and inflammation, providing a mechanistic basis for the observed protective effects. Additionally, vitamin D influences insulin sensitivity, a critical factor in MASLD pathogenesis. Improved insulin sensitivity may mitigate the excessive accumulation of fat in the liver, thus attenuating MASLD progression. In parallel, vitamin D exhibits anti-inflammatory properties by inhibiting pro-inflammatory cytokines implicated in MASLD pathophysiology. Experimental evidence suggests that the immunomodulatory effects of vitamin D extend to the liver, reducing inflammation and oxidative stress, key drivers of MASLD, and the likelihood of hepatocyte injury and fibrosis. Understanding the complex interplay between vitamin D and MASLD provides a basis for exploring targeted therapeutic strategies and preventive interventions. As vitamin D deficiency is a modifiable risk factor, addressing this nutritional concern may prove beneficial in mitigating the burden of MASLD and associated metabolic disorders.

Implications of maternal vitamin D administration for the neonatal respiratory distress syndrome: A randomized clinical trial.

BACKGROUND: Vitamin D deficiency has been suggested to be a risk factor for neonatal respiratory distress syndrome (RDS). This study aimed to evaluate the effect of 25 (OH) D administrations in pregnant women with findings of preterm labor on the incidence of RDS in their preterm neonates. MATERIALS AND METHODS: A randomized controlled clinical trial was conducted on pregnant mothers with gestational age (GA) of less than 34 weeks at risk of preterm delivery. 175 subjects were randomly assigned into two groups, including intervention (intramuscular injection of 50,000 units of 25(OH) D during 72 hours before delivery) and control (no injections). Serum concentrations of 25(OH) D were measured shortly after birth in both mothers and neonates. Then, clinical and laboratory results of mothers and their offspring were recorded (in a checklist). Short-term outcomes and the need for respiratory support were also assessed. Data were analyzed by independent t-test, Mann-Whitney U test, Fisher's exact test, and chi-square test. RESULTS: Even though gestational age, birth weight, delivery method, and serum vitamin D levels are consistent among both groups, 45% of neonates in the control group and 20% in the intervention group developed respiratory distress syndrome (P = 0.05). The mean 25(OH) D level in neonates was 17.7±10.5 and 19.29±9.94 ng/mL in the intervention and control groups, respectively (P > 0.05). CONCLUSION: A single dose of 50,000 units of intramuscular 25(OH)D in pregnant women at risk of preterm labor can lower the risk of RDS in the infant.

Effects of Vitamin D Supplementation on Central Hemodynamic Parameters and Autonomic Nervous System in Obese or Overweight Individuals. / Efeitos da Suplementação de Vitamina D sobre Parâmetros Hemodinâmicos Centrais e Sistema Nervoso Autônomo em Indivíduos com Obesidade ou Sobrepeso.

BACKGROUND: Previous studies have been inconsistent in demonstrating beneficial cardiovascular effects of vitamin D supplementation. OBJECTIVE: To evaluate the effects of vitamin D3 supplementation on central hemodynamic parameters and autonomic activity in obese/overweight individuals with low vitamin D levels (<30ng/dl). METHODS: Adults 40-65 years old with body mass index ≥25<40 kg/m2 were enrolled in this prospective, randomized, double-blind clinical trial (NCT05689632). Central hemodynamics was assessed using the oscillometric method (Mobil-O-Graph®), and heart rate variability using a Polar heart rate monitor (Kubios® software). Patients (n=53) received a placebo in the control group (CO, n=25) or vitamin D3 (VD, n=28) 7000 IU/day, and were evaluated before (W0) and after 8 weeks (W8) with a significance level of 0.05. RESULTS: The groups were homogeneous regarding age (51±6 vs 52±6 years, p=0.509) and vitamin D levels (22.8±4.9 vs 21.7±4.5ng/ml, p=0.590). At W8, the VD group had significantly higher levels of vitamin D (22.5 vs 35.6ng/ml, p<0.001). Only the VD group showed a significant reduction in systolic blood pressure (SBP; 123±15 vs 119±14mmHg, p=0.019) and alkaline phosphatase (213±55 vs 202±55mg/dl, p=0.012). The CO group showed an increase in augmentation pressure (AP: 9 vs 12 mmHg, p=0.028) and augmentation index (AIx: 26 vs 35%, p=0.020), which was not observed in the VD group (AP: 8 vs 8 mmHg, AIx: 26 vs 25%, p>0.05). VD group showed an increase in the parasympathetic nervous system index (PNSi) (-0.64±0.94 vs -0.16±1.10, p=0.028) and the R-R interval (866±138 vs 924±161 ms, p= 0.026). CONCLUSION: In this sample, eight weeks of daily vitamin D supplementation resulted in an improvement in blood pressure levels and autonomic balance.

FUNDAMENTO: Estudos prévios têm sido inconsistentes em demonstrar efeitos cardiovasculares benéficos da suplementação de vitamina D. OBJETIVO: Avaliar efeitos da suplementação de vitamina D3 sobre parâmetros hemodinâmicos centrais e atividade autonômica em indivíduos obesos/sobrepeso e baixos níveis de vitamina D (<30ng/dl). MÉTODOS: Ensaio clínico prospectivo, randomizado, duplo-cego (NCT05689632), adultos 40-65 anos com índice de massa corporal ≥25<40 kg/m2. Hemodinâmica central avaliada por método oscilométrico (Mobil-O-Graph®), variabilidade da frequência cardíaca utilizando frequencímetro Polar (software Kubios®). Os pacientes (n=53) receberam placebo no grupo controle (CO, n=25) ou vitamina D3 (VD, n=28) 7000 UI/dia, avaliados antes (S0) e após 8 semanas (S8) com nível de significância de 0,05. RESULTADOS: Os grupos foram homogêneos na idade (51±6 vs. 52±6 anos, p=0,509) e níveis de vitamina D (22,8±4,9 vs. 21,7±4,5ng/ml, p=0,590). Na S8, o grupo VD apresentou níveis significativamente maiores de vitamina D (22,5 vs. 35,6ng/ml, p<0,001). Apenas o grupo VD mostrou redução significativa da pressão arterial sistólica (PAS; 123±15 vs. 119±14mmHg, p=0,019) e fosfatase alcalina (213±55 vs. 202±55mg/dl, p=0,012). O grupo CO mostrou elevação da pressão de aumento (AP: 9 vs. 12mmHg, p=0,028) e do índice de incremento (Aix: 26 vs. 35%, p=0,020), o que não foi observado no grupo VD (AP: 8 vs. 8mmHg, Aix: 26 vs. 25%, p>0,05). Grupo VD apresentou aumento no índice do sistema nervoso (iSN) parassimpático (-0,64±0,94 vs. -0,16±1,10, p=0,028) e no intervalo R-R (866±138 vs. 924±161ms, p=0,026). CONCLUSÃO: Nesta amostra, a suplementação diária de vitamina D durante oito semanas resultou em melhora dos níveis pressóricos, parâmetros hemodinâmicos centrais e do equilíbrio autonômico.

[The effect of vitamin D deficiency on the content of some soluble signaling molecules in the oral fluid in individuals with dental caries]. / Vliyanie nedostatka vitamina D v organizme na soderzhanie nekotorykh rastvorimykh signal'nykh molekul v rotovoi zhidkosti pri kariese zubov.

OBJECTIVE: The aim of the sthudy is to sthudy the level of soluble Immune Checkpoint Molecules (B7.2, CTLA-4, Tim-3, Lag-3, PD-1) in the oral fluid during dental caries with the background of a lack and/or deficiency of 25-hydroxy-vitamin D in body. MATERIALS AND METHODS: During the research 3 groups of people were formed, each one of them included 17 people aged from 20 to 24 years. The first group included students with high-intensity caries (above 9 DMFt index) and 25-hydroxy-vitamin D levels in blood serum >30 ng/ml, the second included students with high caries intensity and 25-hydroxy-vitamin D levels <30 ng/ml. The control group consisted of students with an average DMFt index of 1.5 (from 0 to 3) and a level of 25(OH)D in the blood more than 30 ng/ml. To determine the content of B7.2 (CD86), CTLA-4, Tim-3, Lag-3, PD-1, the Human Vascular Inflammation Panel 1 multiplex analysis kit from Biolegend (USA) was used. RESULTS: The results of the research showed that during dental caries with a normal level of 25-hydroxy-vitamin D there are no significant changes in the content of Immune Checkpoint Molecules. With the background of deficiency and lack of 25-hydroxy-vitamin D there is a decrease in the amount of B7.2, LAG-3, Tim-3 and PD-1. These changes are being aggravated with an increase of the caries intensity. CONCLUSION: Vitamin D deficiency leads to a decrease in mucosal immunity of the oral cavity, the multiplication of pathogenic microorganisms, which in turn, releasing various metabolites, including cytokine-like substances, aggravate the pathological process and intensify carious lesions.

Neonatal Vitamin D and Associations with Longitudinal Changes of Eczema up to 25 Years of Age.

BACKGROUND: Early-life vitamin D is a potentially modifiable risk factor for the development of eczema, but there is a lack of data on longitudinal associations. METHOD: We measured 25(OH)D3 levels from neonatal dried blood spots in 223 high-allergy-risk children. Latent class analysis was used to define longitudinal eczema phenotype up to 25 years (4 subclasses). Skin prick tests (SPTs) to 6 allergens and eczema outcomes at 6 time points were used to define eczema/sensitization phenotypes. Associations between 25(OH)D3 and prevalent eczema and eczema phenotypes were assessed using logistic regression models. RESULTS: Median 25(OH)D3 level was 32.5 nmol/L (P25-P75 = 23.1 nmol/L). Each 10 nmol/L increase in neonatal 25(OH)D3 was associated with a 26% reduced odds of early-onset persistent eczema (adjusted multinomial odds ratio (aMOR) = 0.74, 95% CI = 0.56-0.98) and 30% increased odds of early-onset-resolving eczema (aMOR = 1.30, 95% CI = 1.05-1.62) when compared to minimal/no eczema up to 12 years. Similar associations were seen for eczema phenotype up to 25 years. We did not see any strong evidence for the association between neonatal 25(OH)D3 and prevalent eczema or eczema/sensitization phenotype. CONCLUSIONS: Higher neonatal 25(OH)D3 levels, a reflection of maternal vitamin D levels in pregnancy, may reduce the risk of early-onset persistent eczema.

Vitamin D and reproductive disorders: a comprehensive review with a focus on endometriosis.

Vitamin D is a fat-soluble steroid hormone that was initially known only for regulating calcium and phosphorus levels and maintaining bone health. However, it was later discovered that many organs express vitamin D metabolizing enzymes and have a ligand for vitamin D, which regulates the expression of an extensive assortment of genes. As a result, vitamin D is indispensable for the proper function of organs, and its deficiency is believed to be a critical factor in symptoms and disorders such as cardiovascular diseases, autoimmune diseases, and cancers. The significance of vitamin D in reproductive tissues was recognized later, and studies have revealed its crucial role in male and female fertility, as well as proper reproductive function during pregnancy. Vitamin D deficiency has been identified as a risk factor for infertility, gonadal cancers, pregnancy complications, polycystic ovary syndrome, and endometriosis. However, data investigating the association between vitamin D levels and reproductive disorders, including endometriosis, have encountered inconsistencies. Therefore, the present study aims to review existing research on the effect of vitamin D on proper reproductive function, and the role of deficiency in reproductive diseases and specifically focuses on endometriosis.

The role of vitamin D in pediatric systemic lupus erythematosus - a double pawn in the immune and microbial balance.

Having increased popularity during the Covid-19 pandemic, vitamin D3 is currently impressing thanks to the numerous researches aimed at its interactions with the body's homeostasis. At the same time, there is a peak in terms of recommendations for supplementation with it. Some of the studies focus on the link between autoimmune diseases and nutritional deficiencies, especially vitamin D3. Since the specialized literature aimed at children (patients between 0-18 years old) is far from equal to the informational diversity of the adult-centered branch, this review aims to bring up to date the relationship between the microbial and nutritional balance and the activity of pediatric systemic lupus erythematosus (pSLE). The desired practical purpose resides in a better understanding and an adequate, individualized management of the affected persons to reduce morbidity. The center of the summary is to establish the impact of hypovitaminosis D in the development and evolution of pediatric lupus erythematosus. We will address aspects related to the two entities of the impact played by vitamin D3 in the pathophysiological cascade of lupus, but also the risk of toxicity and its effects when the deficiency is over supplemented (hypervitaminosis D). We will debate the relationship of hypovitaminosis D with the modulation of immune function, the potentiation of inflammatory processes, the increase of oxidative stress, the perfusion of cognitive brain areas, the seasonal incidence of SLE and its severity. Finally, we review current knowledge, post-pandemic, regarding the hypovitaminosis D - pSLE relationship.

Vitamin D effects on Chlamydia trachomatis infection: a case-control and experimental study.

Introduction: Vitamin D deficiency is the most common nutritional deficiency worldwide. Chronic vitamin D deficiency causes immune system dysfunction, which increases susceptibility to pathogens such as bacteria, especially intracellular parasites, and viruses. Chlamydia trachomatis (C. t) is an obligate intracellular parasitic bacterium that causes a variety of sequelae. We speculated that vitamin D might be associated with C. t infection. This study aimed to address this gap in knowledge by investigating the relationship between vitamin D and C. t infection using both in vitro and in vivo models. Methods and results: The addition of calcitriol to McCoy cell culture in vitro delayed and reduced the quantity and volume of inclusions compared to the control group. Macrophages of peritoneally lavaged mice co-cultured with McCoy decreased the infection rate and delayed the appearance of inclusions. In mice models of vitamin D deficiency, mice in the VD-group exhibited more severe genital tract inflammation and a longer duration of infection after inoculation with C. t in the genital tract. Supplementing these mice with vitamin D3 during treatment enhanced the therapeutic effect of antibiotics. We also conducted a case-control study involving 174 C. t-positive patients (95 males and 79 females) and 380 healthy volunteers (211 males and 169 females) aged 20-49 from January 2016 to March 15, 2017. Serum 25-(OH)D concentration was measured by assessing morning fasting blood samples of healthy volunteers and C. t-positive patients 1 day before antibiotic treatment and the next day after one course of treatment. The patients were followed up for 1 month and evaluated for recovery. The results showed that vitamin D deficiency was a risk factor for C. t infection and treatment failure. Conclusion: In summary, findings from experimental and clinical studies indicate a close association between vitamin D levels and C. t infection and treatment outcomes. Given the affordability and safety of vitamin D, both healthy individuals and patients should focus on vitamin D intake. Vitamin D supplementation could enhance treatment success and should be used as an adjunctive therapy alongside antibiotic therapy for C. t infections, pending confirmation in larger, prospective, randomized controlled trials.