Vitamin D Intake, Serum 25-Hydroxyvitamin-D (25(OH)D) Levels, and Cancer Risk: A Comprehensive Meta-Meta-Analysis Including Meta-Analyses of Randomized Controlled Trials and Observational Epidemiological Studies

Enhancing the Design of Nutrient Clinical Trials for Disease Prevention-A Focus on Vitamin D: A Systematic Review

OBJECTIVES

This systematic review (SR) highlights principles for nutrient clinical trials and explore the diverse physiological functions of vitamin D beyond its traditional role in the musculoskeletal system related to clinical study designs.

BACKGROUND

Thousands of published research articles have investigated the benefits of vitamin D (a nutrient example taken in this SR) beyond the musculoskeletal system, including the immune, pulmonary, and cardiovascular systems; pregnancy; autoimmune disorders; and cancer. They illustrated vitamin D's molecular mechanisms, interactions, and genomic and nongenomic actions.

METHODS

This SR was designed to identify shortcomings in clinical study designs, statistical methods, and data interpretation that led to inconsistent findings in vitamin D-related publications. SR also highlights examples and insights into avoiding study design errors in future clinical studies, including randomized controlled clinical trials (RCTs). The SR adheres to the latest PRISMA statement, guidelines, and the PICOS process.

RESULTS

Inappropriate or flawed study designs were frequent in clinical trials. Major failures discussed here include too short clinical study duration, inadequate or infrequent doses, insufficient statistical power, failure to measure baseline and achieved levels, and recruiting vitamin D-sufficient participants. These design errors have led to misleading interpretations. Thus, conclusions from such studies should not be generalized or used in guidelines, recommendations, or policymaking.

CONCLUSION

Adequately powered epidemiological studies and RCTs with sufficient vitamin D and duration in individuals with vitamin D deficiency reported favorable clinical outcomes, enriching the literature, enabling to understand its physiology and mechanisms. Proper study designs with rigorous methodologies and cautious interpretation of outcomes are crucial in advancing the nutrient field. The principles discussed apply not only to vitamin D, but also other micro-nutrients and nutraceutical research. Adhering to them enhances the credibility and reliability of clinical trials, SRs, and meta-analysis outcomes. The study emphasizes the importance of focused, hypothesis-driven, well-designed, statistically powered RCTs to explore the diverse benefits of nutrients, conducted in index nutrient deficient participants, and avoidance of study design errors. Findings from such studies should be incorporated into clinical practice, policymaking, and public health guidelines, improving the health of the nation and reducing healthcare costs.

The status of serum 25(OH)D levels is related to breast cancer

AIM

Breast cancer is the second most common cancer among women and the leading cause of cancer-related mortality in this population. Numerous factors have been identified as either risk factors or protective factors for breast cancer. However, the role of Vitamin D (Vit. D) in breast cancer remains contentious, with conflicting findings in the literature. The present study aimed to compare serum Vit. D levels between women with and without breast cancer.

METHODS

This cross-sectional study included 40 women diagnosed with breast cancer, referred to the Mahdia Hamadan Radiotherapy Center in 2022. These participants were matched with 40 age- and Vit. D serum level-matched women without breast cancer. Serum Vit. D levels were measured using the ELISA method. Statistical analysis was performed using SPSS version 26, with a significance threshold set at a 95% confidence level.

RESULTS

The mean ± standard deviation of serum Vit. D levels in women with and without breast cancer were 31.9 ± 28.27 ng/mL and 37.98 ± 15.89 ng/mL, respectively (P = 0.024). The prevalence of Vit. D insufficiency was 50% in the breast cancer group and 27.5% in the control group, while 50% of the breast cancer group and 72.5% of the control group had sufficient Vit. D levels (P = 0.008). In women with breast cancer, lower Vit. D levels were significantly associated with lower educational (P < 0.001), economic (P < 0.001), and social status (P < 0.001). A weak positive correlation was observed between serum Vit. D levels and patient age (r = 0.162, P = 0.152).

CONCLUSION

The significant difference in serum Vit. D levels between women with and without breast cancer suggests that Vit. D deficiency may be associated with breast cancer risk. These findings support the hypothesis that improving Vit. D status in women could potentially reduce the incidence of breast cancer.

Melatonin and vitamin D as potential synergistic adjuvants for cancer therapy (Review)

Significant advancements have been made in cancer therapy; however, limitations remain with some conventional approaches. Adjuvants are agents used alongside primary treatments to enhance their efficacy and the treatment outcomes of patients. Modern lifestyles contribute to deficiencies in melatonin and vitamin D. Limited sun exposure affects vitamin D synthesis, and artificial light at night suppresses melatonin production. Both melatonin and vitamin D possess anti‑inflammatory, immune‑boosting and anticancer properties, rendering them potential adjuvants of interest. Studies suggest melatonin and vitamin D supplementation may address antioxidant imbalances in lip, oral and pharyngeal cancers. Moreover, promising results from breast, head and neck, brain, and osteosarcoma research indicate potential for tumor growth inhibition, improved survival, and a better quality of life of patients with cancer. The radioprotective properties of melatonin and vitamin D are another exciting area of exploration, potentially enhancing radiotherapy effectiveness while reducing side effects. For its part, the sleep‑promoting effects of melatonin may indirectly benefit patients with cancer by influencing the immune system. Thus, the prevalence of vitamin D and melatonin deficiencies highlights the importance of supplementation, as lower levels can worsen side‑effects from cancer treatments. The present review explores the potential of combining melatonin and vitamin D as synergistic adjuvants for cancer therapy. These agents have shown promise individually in cancer prevention and treatment, and their combined effects warrant investigation. Therefore, large‑scale controlled trials are crucial to definitively determine the optimal dosage, safety and efficacy of this combination in improving the lives of patients with cancer.

Vitamin D and major chronic diseases

Numerous observational studies have demonstrated a significant inverse association between vitamin D status and the risk of major chronic disease, including type 2 diabetes (T2D), cardiovascular disease (CVD), and cancer. However, findings from Mendelian randomization (MR) studies and randomized controlled trials (RCTs) suggest minimal or no benefit of increased vitamin D levels. We provide an overview of recent literature linking vitamin D to major chronic diseases. Because emerging evidence indicates a potential threshold effect of vitamin D, future well-designed studies focused on diverse populations with vitamin D deficiency or insufficiency are warranted for a more comprehensive understanding of the effect of maintaining sufficient vitamin D status on the prevention of major chronic diseases.

A real-world study of active vitamin D as a prognostic marker in patients with sarcoma

PURPOSE

The assessment of sarcoma during clinical practice is primarily based on imaging examination, with no effective biomarkers available. Although it has been established that 1,25(OH)2D3 is abnormally expressed in patients with sarcoma, it remains unclear whether 1,25(OH)2D3 level could be used as an evaluation marker in these patient population.

METHODS

This real-world study investigated 1,25(OH)2D3 level and its association with clinical features in sarcoma patients. Data on 1,25(OH)2D3, parathyroid hormone, calcium, and calcitonin were collected from 331 patients with sarcoma, while the imaging results and the variation in 1,25(OH)2D3 among 213 patients with sarcoma before and after treatment was further analyzed.

RESULTS

We found that the serum 1,25(OH)2D3 level was predominantly decreased in patients with sarcoma, with a mean of 45.68 nmol/L. 1,25(OH)2D3 was significantly correlated with the gender and age of sarcoma patients, with more substantial reductions in women and younger patients. Among sarcoma patients, those with progressive disease exhibited a 7.08 nmol/L (-13.73%) decrease in serum 1,25(OH)2D3 levels compared to baseline, while patients with non-progressive disease showed a 1.11 nmol/L (+ 7.0%) increase.

CONCLUSION

The variation of serum 1,25(OH)2D3 can predict the disease status of patients with sarcoma. Decreased serum 1,25(OH)2D3 levels are indicative of disease progression in sarcoma patients, suggesting its potential for application as a prognostic marker for disease assessment in this patient population.

Plasma 25-hydroxyvitamin D deficiency in the peri-operative period is associated with survival outcome in colorectal cancer patients: a meta-analysis

AIM

Surgery had a significant impact on 25-hydroxyvitamin D (25-(OH)D) levels. Uncertainty still existed regarding the effects of peri-operative 25(OH)D deficiency on colorectal cancer (CRC) patients' prognosis. The purpose of the present study was to explore the potential association between the peri-operative 25(OH)D deficiency and the survival outcome of CRC.

METHODS

Seven electronic databases [including PubMed, EMBASE, Web of Science, The Cochrane Library, OvidMEDLINE(R), China National Knowledge Infrastructure (CNKI) and Wangfang data] were searched without language limitations. The primary outcomes were overall survival and all-cause mortality. Secondary outcomes were the incidence of 25(OH)D deficiency and risk variables for low 25(OH)D level in the peri-operative period.

RESULTS

14 eligible studies were obtained with 9324 patients for meta-analysis. In the peri-operative period, the pooled incidence of blood 25(OH)D deficiency was 59.61% (95% CI: 45.74-73.48). The incidence of blood 25(OH)D deficiency post-operatively (66.60%) was higher than that pre-operatively (52.65%, 95% CI: 32.94-72.36). Male (RR = 1.09, 95% CI: 1.03-1.16), rectum tumor (RR = 1.23, 95% CI: 1.03-1.47), spring and winter sampling (RR = 1.24, 95% CI: 1.02-1.49) were the risk factors for the 25(OH)D deficiency. The association between the low 25(OH)D post-operatively and short-term overall survival (HR = 0.43, 95% CI: 0.24-0.77) was most prominent, while a low 25(OH)D pre-operatively (HR = 0.47, 95% CI: 0.31-0.70) was more significantly associated with long-term all-cause mortality than that after surgery.

CONCLUSION

Peri-operative 25(OH)D impacted the CRC patients' prognosis. Due to possible confounding effects of systemic inflammatory response (SIR), simultaneous measurement of vitamin D and SIR is essential for colorectal survival.

Genetically Determined Circulating Lactase/Phlorizin Hydrolase Concentrations and Risk of Colorectal Cancer: A Two-Sample Mendelian Randomization Study

Previous research has found that milk is associated with a decreased risk of colorectal cancer (CRC). However, it is unclear whether the milk digestion by the enzyme lactase-phlorizin hydrolase (LPH) plays a role in CRC susceptibility. Our study aims to investigate the direct causal relationship of CRC risk with LPH levels by applying a two-sample Mendelian Randomization (MR) strategy. Genetic instruments for LPH were derived from the Fenland Study, and CRC-associated summary statistics for these instruments were extracted from the FinnGen Study, PLCO Atlas Project, and Pan-UK Biobank. Primary MR analyses focused on a cis-variant (rs4988235) for LPH levels, with results integrated via meta-analysis. MR analyses using all variants were also undertaken. This analytical approach was further extended to assess CRC subtypes (colon and rectal). Meta-analysis across the three datasets illustrated an inverse association between genetically predicted LPH levels and CRC risk (OR: 0.92 [95% CI, 0.89-0.95]). Subtype analyses revealed associations of elevated LPH levels with reduced risks for both colon (OR: 0.92 [95% CI, 0.89-0.96]) and rectal cancer (OR: 0.92 [95% CI, 0.87, 0.98]). Consistency was observed across varied analytical methods and datasets. Further exploration is warranted to unveil the underlying mechanisms and validate LPH's potential role in CRC prevention.

Association between the Serum Vitamin D Concentration and All-Cause and Cancer-Specific Mortality in Individuals with Cancer

We aimed to explore the association between the serum 25-hydroxyvitamin D concentration and all-cause and cancer-specific mortality in 2,463 adult patients with cancer from the National Health and Nutrition Examination Survey 2007-2018. We linked mortality data from the survey to the National Death Index records up to December 31, 2019. During a median follow-up period of 70 months, 567 patients died, of whom 194 died due to cancer. Multivariate adjustment was performed for demographic characteristics, lifestyle, dietary factors, 25-hydroxyvitamin D testing period, and cancer site. Higher serum 25-hydroxyvitamin D concentrations up to 75 nmol/L significantly reduced the risk of all-cause and cancer-specific mortality. When 25-hydroxyvitamin D quartiles were compared, the multivariable-adjusted hazard ratios were 0.59 (95% confidence interval: 0.42, 0.84) for all-cause mortality (P for trend <0.001) and 0.48 (95% confidence interval: 0.29, 0.79) for cancer-specific mortality (P for trend = 0.037) in quartile 3 (79.3-99.2 nmol/L). A threshold of 75 nmol/L for serum 25-hydroxyvitamin D may represent an intervention target to reduce mortalities in patients with cancer, and maintaining 25(OH)D concentrations within range (79.3-99.2 nmol/L) is beneficial for reducing all-cause and cancer-specific mortality.

Utilizing logistic regression to compare risk factors in disease modeling with imbalanced data: a case study in vitamin D and cancer incidence

Imbalanced data, a common challenge encountered in statistical analyses of clinical trial datasets and disease modeling, refers to the scenario where one class significantly outnumbers the other in a binary classification problem. This imbalance can lead to biased model performance, favoring the majority class, and affecting the understanding of the relative importance of predictive variables. Despite its prevalence, the existing literature lacks comprehensive studies that elucidate methodologies to handle imbalanced data effectively. In this study, we discuss the binary logistic model and its limitations when dealing with imbalanced data, as model performance tends to be biased towards the majority class. We propose a novel approach to addressing imbalanced data and apply it to publicly available data from the VITAL trial, a large-scale clinical trial that examines the effects of vitamin D and Omega-3 fatty acid to investigate the relationship between vitamin D and cancer incidence in sub-populations based on race/ethnicity and demographic factors such as body mass index (BMI), age, and sex. Our results demonstrate a significant improvement in model performance after our undersampling method is applied to the data set with respect to cancer incidence prediction. Both epidemiological and laboratory studies have suggested that vitamin D may lower the occurrence and death rate of cancer, but inconsistent and conflicting findings have been reported due to the difficulty of conducting large-scale clinical trials. We also utilize logistic regression within each ethnic sub-population to determine the impact of demographic factors on cancer incidence, with a particular focus on the role of vitamin D. This study provides a framework for using classification models to understand relative variable importance when dealing with imbalanced data.