Effect of vitamin D supplementation on non-skeletal disorders: a systematic review of meta-analyses and randomised trials

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.

Vitamin D status in Norwegian children and associations between child vitamin D status, dietary factors, and maternal vitamin D status

Background and aims

There is limited data regarding the vitamin D status of infants and young children in Norway. We aimed to assess vitamin D status among Norwegian children at approximately 6 and 12 months of age and explore associations between child vitamin D status, dietary factors, and maternal vitamin D status.

Methods

Mothers/parents completed a food frequency questionnaire for their 6/12-month-old child. Dried blood spot samples were collected from the mother and child.

Results

The mean serum 25-hydroxyvitamin D (S-25(OH)D) concentration was 81 nmol/L (standard deviation [SD] 22 nmol/L) for 6-month-old children (n = 84) and 72 nmol/L (SD 22 nmol/L) for 12-month-old children (n = 56) (P = 0.03 for difference between age groups). In the younger and older age groups, 94 and 88% of the children, respectively, had a S-25(OH)D concentration ≥ 50 nmol/L. The mean dietary vitamin D intake was 12 μg/day for the 6-month-olds and 14 μg/day for the 12-month-olds. Adjusted linear regression models showed that for every μg/day increase in dietary vitamin D intake, serum 25(OH)D (nmol/L) increased by around one nmol/L for both age groups (P = 0.002 for the younger age group and P = 0.04 for the older age group). Use of vitamin D supplements was associated with higher S-25(OH)D concentrations in both age groups, while a higher S-25(OH)D concentration among formula users was found only in the youngest age group. Breastfeeding was not associated with S-25(OH)D concentration in either age group. Small positive correlations between child and maternal vitamin D status were observed for both the younger (r = 0.22) and the older (r = 0.28) age groups (P = 0.04 for both groups).

Conclusion

While there was a wide range in S-25(OH)D concentrations among children, most were within the sufficient range. Adequate vitamin D intake should be encouraged both in the first and second year of life.

Effects of a Novel Dispersible Supplement Containing 2500 IU of Vitamin D and 1000 µg of B12 in Restoring Vitamin D and B12 Insufficiency: A Multicenter, Randomized Controlled Trial

BACKGROUND/OBJECTIVES

Vitamins D and B12 play a crucial role in maintaining bone health, immune function, and neurological integrity. Combined deficiencies in these vitamins can lead to severe health consequences. Current treatment approaches, such as dietary changes and single-vitamin supplementation, often fail to address these deficiencies comprehensively. This study evaluates the effectiveness of concurrent vitamin D and B12 supplementation to correct these insufficiencies.

METHODS

A prospective, multicenter, randomized controlled trial was conducted in Greece from October 2024 to December 2024. Participants aged 20 to 80 years, with insufficient levels of 25-hydroxyvitamin D (serum < 20 ng/mL) and B12 (serum < 250 ng/L), were eligible for inclusion.

RESULTS

A total of 124 patients were randomized into three groups: one receiving vitamins B12 and D in a single supplement (2500 IU + 1000 mcg), one receiving separate doses of each vitamin (2000 IU + 1000 mcg), and a control group receiving no supplementation. The results demonstrated a significant increase in B12 and 25-hydroxyvitamin D levels among the supplemented groups. Particularly, participants in the combined supplementation group showed higher average serum levels of both vitamins. By the end of this study, 37.1% of those in the combined supplement group achieved adequate vitamin levels, compared to 29.4% in the separate supplementation group.

CONCLUSIONS

In conclusion, combined supplementation may improve patient adherence and compliance, leading to better health outcomes for individuals with combined vitamins D and B12 deficiencies.

Variations in vitamin D status among Chinese children aged 1-6 years during the COVID-19 pandemic

Background

Vitamin D deficiency has been a critical global health issue within the pediatric population. Closed-off management brought about by the COVID-19 pandemic has drastically impacted outdoor activities and sunlight exposure, however, whether it indirectly further exacerbated the vitamin D deficiency has not been largely investigated, especially among children in China. The purpose of this study was to evaluate 25(OH)D concentrations in children before and during the COVID-19 lockdown and to analyze the factors influencing their vitamin D status.

Methods

A cross-sectional survey included children aged 1-6 years from Han Zhong Central Hospital in the southern Shanxi Province of China. This study examined healthy children from a pediatric health care department over two periods: before COVID-19 (March 2019-February 2020), and during COVID-19 (March 2020-February 2021). Total 25(OH)D concentrations were compared between the two observation periods. Vitamin D status was determined by 25(OH)D concentrations: deficient (<20 ng/ml), insufficient (20-29 ng/ml), and sufficient (30-100 ng/ml).

Results

The study involved 6,780 children, with 52.8% being 1-year-olds, 23.1% being 2-year-olds, and 24.1% being 3 to 6-year-olds. Boys and girls were 52.8 and 47.2%, respectively. The actual prevalence of deficiency in vitamin D nutritional status among children was 2.8%, with 87.1% of cases in those aged 3 to 6 years. Vitamin D insufficiency was 18.3%, affecting 54.8% of the same demographic. The average of 25(OH)D concentration were 38.2 ± 9.8 ng/ml, significantly varying by age and season. 25(OH)D concentrations decreased with age, from 42.3 ± 8.8 ng/ml at 1-year-olds to 37.4 ± 8.2 ng/ml at 2-year-olds, and further to 30.2 ± 8.1 ng/ml at 3 to 6-year-olds. Seasonal variations showed that 25(OH)D concentrations were higher in spring (38.7 ± 10.1 ng/ml), summer (38.7 ± 10.0 ng/ml), and fall (38.6 ± 9.2 ng/ml) in comparison to winter (36.0 ± 9.8 ng/ml). Additionally, the concentrations of 25(OH)D in spring exhibited a decrease during the COVID-19 pandemic (37.9 ± 10.3 ng/ml) in comparison to the pre-pandemic measurements (39.3 ± 9.9 ng/ml) (p = 0.008), while winter concentrations increased from (35.1 ± 10.4 ng/ml) to (37.9 ± 10.3 ng/ml) during the pandemic (p = 0.002).

Conclusion

The research indicated that vitamin D deficiency is uncommon among Chinese children, with 25(OH)D concentrations experiencing a notable decline in those aged 3-6 years. The findings suggested a potential need for tailored supplementation strategies and possibly higher doses for this age group, along with monitoring 25(OH)D concentrations to evaluate supplementation effectiveness. COVID-19-related restrictions minimally affected children's 25(OH)D concentrations, revealing the nutritional implications of the pandemic.

Vitamin D, acute respiratory infections, and Covid-19: The curse of small-size randomised trials. A critical review with meta-analysis of randomised trials

BACKGROUND

Randomised trials conducted from 2006 to 2021 indicated that vitamin D supplementation (VDS) was able to prevent severe COVID-19 and acute respiratory infections (ARI). However, larger randomised trials published in 2022 did not confirm the health benefits of VDS in COVID-19 patients.

OBJECTIVE

To examine through a systematic review with meta-analysis the characteristics of randomised trials on VDS to COVID-19 patients and admission to intensive care unit (ICU), and of randomised trials on VDS for the prevention of ARI.

METHOD

A systematic search retrieved randomised trials on VDS to COVID-19 patients and admission to ICU. Data on VDS and ARI were extracted from the meta-analysis of Jolliffe et al. 2021. Groups were formed including trials with total numbers of patients below or above the median size of all trials. The associations between VDS vs no VDS, and admission to ICU were evaluated using random-effects models from which summary odds ratios (SOR) and 95% confidence intervals (CI) were obtained. Meta-analyses were done for all trials and for each group of trials, which allowed testing a possible effect modification of trial size. Publication bias was assessed using the Louis-Furuya-Kanaruori (LFK) index (no bias if index between -1 and +1) and the trim and fill method.

RESULTS

Nine trials on VDS for preventing admission to ICU were identified, including 50 to 548 patients. The summary odds ratio (SOR) was 0.61 (95% CI: 0.39-0.95) for all trials, 0.34 (0.13-0.93) for trials including 50 to <106 patients and 0.88 (0.62-1.24) for trials including 106 to 548 patients (interaction p = 0.04). The LFK index was -3.79, and after trim and fill, the SOR was 0.80 (0.40-1.61). The SOR for the 37 trials on VDS for ARI prevention included 25 to 16,000 patients. The SOR was 0.92 (0.86-0.99) for all trials, 0.69 (0.57-0.83) for trials including 25 to <248 patients and 0.98 (0.94-1.03) for trials including 248 to 16,000 patients (interaction p = 0.0001). The LFK index was -3.11, and after trim and fill, the SOR was 0.96 (0.88-1.05).

CONCLUSION

Strong publication bias affected small randomised trials on VDS for the prevention of severe COVID-19 and of ARI. Systematic reviews should beware of small-size randomised trials that generally exaggerate health benefits.

Vitamin D: Evidence-Based Health Benefits and Recommendations for Population Guidelines

Vitamin D offers numerous under-recognized health benefits beyond its well-known role in musculoskeletal health. It is vital for extra-renal tissues, prenatal health, brain function, immunity, pregnancy, cancer prevention, and cardiovascular health. Existing guidelines issued by governmental and health organizations are bone-centric and largely overlook the abovementioned extra-skeletal benefits and optimal thresholds for vitamin D. In addition, they rely on randomized controlled trials (RCTs), which seldom show benefits due to high baseline 25-hydroxyvitamin D [25(OH)D] concentrations, moderate supplementation doses, and flawed study designs. This review emphasizes the findings from prospective cohort studies showing that higher 25(OH)D concentrations reduce the risks of major diseases and mortality, including pregnancy and birth outcomes. Serum concentrations > 30 ng/mL (75 nmol/L) significantly lower disease and mortality risks compared to <20 ng/mL. With 25% of the U.S. population and 60% of Central Europeans having levels <20 ng/mL, concentrations should be raised above 30 ng/mL. This is achievable through daily supplementation with 2000 IU/day (50 mcg/day) of vitamin D3, which prevent diseases and deaths. Furthermore, a daily dose between 4000 and 6000 IU of vitamin D3 to achieve serum 25(OH)D levels between 40 and 70 ng/mL would provide greater protection against many adverse health outcomes. Future guidelines and recommendations should integrate the findings from observational prospective cohort studies and well-designed RCTs to improve public health and personalized care.

Association of serum vitamin D level and live birth rate in women undergoing frozen embryo transfer-a retrospective cohort study

PURPOSE

To assess the association of serum vitamin D level and the live birth rate in women undergoing frozen embryo transfer (FET).

METHODS

This is a retrospective cohort study involving 1489 infertile women who had frozen embryo transfer at two tertiary reproductive medicine centres from 2019 to 2021. Only the first frozen embryo transfer was included for women who had repeated transfers during the period. Archived serum samples taken at LH surge or before the start of progestogens for FET were analysed for 25(OH)D levels using mass spectrometry. The main outcome measure was the live birth rate. Vitamin D deficiency was defined as serum 25(OH)D < 50 nmol/l (< 20 ng/ml) based on the Endocrine Society Clinical Practice guidelines.

RESULTS

The median age was 36 (25th-75th percentile 34-38) years. 37.7% (561/1489) women had cleavage stage embryo transfer and 62.3% (928/1489) women had blastocyst transfer. When analysing the results based on the threshold in the Endocrine Society guideline of 50 nmol/l (20 ng/ml) for vitamin D deficiency, there were no statistically significant differences in the live birth rate in the vitamin D deficient and non-deficient groups [151/489 (30.9%) vs 341/998 (34.2%), OR 0.861, 95% CI 0.683-1.086 P = 0.205]. There were no statistically significant differences in the pregnancy rates, ongoing pregnancy rates, and miscarriage rates between the two groups.

CONCLUSION

Serum vitamin D is not associated with birth rate in women undergoing FET.

Effects of High-Dose Vitamin D3 Supplementation on Pig Performance, Vitamin D Content in Meat, and Muscle Transcriptome in Pigs

Vitamin D is known for its role in calcium homeostasis, bone health, and immune function. Recent research has explored its effects on muscle functionality and meat quality in pigs. This study examined high-dose vitamin D3 supplementation in pigs, focusing on growth, blood and tissue vitamin D3 levels, and muscle transcriptome changes. Thirty pigs were divided into three groups, given different amounts of oral supplementation: control, 5000 IU/kg and 10,000 IU/kg vitamin D3. Biochemical and haematological blood parameters, vitamin D content in blood and muscle, and kidney calcium content were evaluated. RNA-seq and qPCR analysed muscle transcriptome changes, while gene set enrichment analysis (GSEA) identified gene expression enrichments. Results showed that 5000 IU/kg vitamin D3 supplementation altered blood parameters like platelet anisocytosis and glucose levels but did not affect body weight, weight gain, or feed intake. Kidney calcium content increased with supplementation. The muscle (longissimus dorsi) vitamin D content increased, suggesting the potential for biofortified pork, although still not optimal as a dietary vitamin D source. Transcriptome analysis revealed minimal gene expression changes, with only the interferon-gamma receptor 2 (IFNGR2) gene differentially expressed at the highest dose. GSEA indicated enrichment in ATP metabolic processes and electron transport chain genes in the 5000 IU/kg group, and immune system, cholesterol, steroid, and fatty acid metabolism genes in the 10,000 IU/kg group. Despite literature suggesting a role for vitamin D in muscle gene expression and growth improvement, this study found its effects limited.

Polymorphisms of the Vitamin D Binding Protein (VDBP) and Free Vitamin D in Patients with Cystic Fibrosis

OBJECTIVES/BACKGROUND

Vitamin D-binding protein (VDBP) and free vitamin D are new markers that are being studied as a possible markers of vitamin D status. The main aim of our study was to analyze the VDBP genotype and quantify the levels of free vitamin D in a sample of cystic fibrosis (CF) patients.

METHODS

We conducted a multicenter, cross-sectional, and prospective study including patients with CF and exocrine pancreatic insufficiency who were clinically stable. We investigated vitamin D levels (total and free) and the different VDBP haplotypes. Free vitamin D levels were measured using an electro-chemiluminescence assay.

RESULTS

A sample of 48 patients was obtained (52% male; median age 13.8 years). The most common allele of VDBP was Gc1s (72%) > Gc2 (52%) > Gc1f (27%). The median calcidiol was 21.2 ng/mL (IR 15.3-26.9), and 81% had levels in the insufficiency range: 23 patients (48%) below 20 ng/mL, and 16 (33%) between 20 and 30 ng/mL. The median free vitamin D level was 4.2 pg/mL (IR 3.9-5.6). A positive correlation was observed between calcidiol and free vitamin D levels (r = 0.871; p < 0.0001). After adjustment for season, vitamin D supplementation, sex, and CF-related diabetes, patients with Gc1f polymorphism had a lower risk of vitamin D deficiency, OR 0.22 (95% CI 0.05-0.99), and p = 0.027. A negative linear trend was observed between the polymorphisms grouped into three categories (Gc1/Gc1, Gc1/Gc2, and Gc2/Gc2, in that order) and vitamin D and free vitamin D levels (p = 0.025 and p = 0.033, respectively).

CONCLUSION

In CF, as in the general population, the most common VDBP haplotype in the Caucasian race is Gc1s. VDBP polymorphisms influence serum vitamin D and free vitamin D levels in CF patients. There is a good correlation between free vitamin D and calcidiol levels, suggesting that measuring the latter in CF does not seem to provide any additional benefit.

Is Micronutrient Supplementation Helpful in Supporting the Immune System during Prolonged, High-Intensity Physical Training?

It is well known that during prolonged, high-intensity physical training, athletes experience a state of immunosuppression and that balanced nutrition can help maintain immunity. This review summarizes the effects (amplified by virus infection) of high-intensity, long-term exercise on immunity, critically presenting key micronutrients and supplementation strategies that can influence athletes' performance and their immune system. The main conclusion is that micronutrient supplementation with diet could help to protect the immune system from the stress effects induced by intense physical activities. The importance of personalized supplementation has been also recommended.

Umbrella Review on the Relationship between Vitamin D Levels and Cancer

BACKGROUND

Cancer is a growing public health problem and cancer is linked to vitamin D via several mechanisms. Recent umbrella reviews on the extra-skeletal effects of vitamin D did not turn their attention to cancer. Accordingly, an overview of the current state of research is needed.

MATERIALS AND METHODS

An umbrella review was conducted to provide an overview of systematic reviews on the association between vitamin D and incidence or mortality of breast cancer, colorectal cancer, lung cancer, pancreatic cancer, and prostate cancer.

RESULTS

Inverse correlations were found between the vitamin D level (measured by circulating 25(OH)D) and mortality for all five types of cancer. For breast cancer, colorectal cancer, lung cancer, and pancreatic cancer, there are also hints of a lower incidence due to higher 25(OH)D levels.

CONCLUSION

As most reviews include observational studies, conclusions on causality cannot be made. Methodological differences between the included reviews and different study designs in the individual studies lead to methodological problems. Despite these problems, the review shows inverse correlations between 25(OH)D levels and mortality, and mostly inverse correlations between 25(OH)D levels and incidence.

Sunlight: Time for a Rethink?

UVR is a skin carcinogen, yet no studies link sun exposure to increased all-cause mortality. Epidemiological studies from the United Kingdom and Sweden link sun exposure with reduced all-cause, cardiovascular, and cancer mortality. Vitamin D synthesis is dependent on UVB exposure. Individuals with higher serum levels of vitamin D are healthier in many ways, yet multiple trials of oral vitamin D supplementation show little benefit. Growing evidence shows that sunlight has health benefits through vitamin D-independent pathways, such as photomobilization of nitric oxide from cutaneous stores with reduction in cardiovascular morbidity. Sunlight has important systemic health benefit as well as risks.

Advances in biomedical applications of vitamin D for VDR targeted management of obesity and cancer

BACKGROUND

1,25(OH)2D3 is a fat-soluble vitamin, involved in regulating Ca2+ homeostasis in the body. Its storage in adipose tissue depends on the fat content of the body. Obesity is the result of abnormal lipid deposition due to the prolonged positive energy balance and increases the risk of several cancer types. Furthermore, it has been associated with vitamin D deficiency and defined as a low 25(OH)2D3 blood level. In addition, 1,25(OH)2D3 plays vital roles in Ca2+-Pi and glucose metabolism in the adipocytes of obese individuals and regulates the expressions of adipogenesis-associated genes in mature adipocytes.

SCOPE AND APPROACH

The present contribution focused on the VDR mediated mechanisms interconnecting the obese condition and cancer proliferation due to 1,25(OH)2D3-deficiency in humans. This contribution also summarizes the identification and development of molecular targets for VDR-targeted drug discovery.

KEY FINDINGS AND CONCLUSIONS

Several studies have revealed that cancer development in a background of 1,25(OH)2D3 deficient obesity involves the VDR gene. Moreover, 1,25(OH)2D3 is also known to influence several cellular processes, including differentiation, proliferation, and adhesion. The multifaceted physiology of obesity has improved our understanding of the cancer therapeutic targets. However, currently available anti-cancer drugs are notorious for their side effects, which have raised safety issues. Thus, there is interest in developing 1,25(OH)2D3-based therapies without any side effects.

Skin cancers are the most frequent cancers in fair-skinned populations, but we can prevent them

Cancers of the skin are the most commonly occurring cancers in humans. In fair-skinned populations, up to 95% of keratinocyte skin cancers and 70-95% of cutaneous melanomas are caused by ultraviolet radiation and are thus theoretically preventable. Currently, however, there is no comprehensive global advice on practical steps to be taken to reduce the toll of skin cancer. To address this gap, an expert working group comprising clinicians and researchers from Africa, America, Asia, Australia, and Europe, together with learned societies (European Association of Dermato-Oncology, Euromelanoma, Euroskin, European Union of Medical Specialists, and the Melanoma World Society) reviewed the extant evidence and issued the following evidence-based recommendations for photoprotection as a strategy to prevent skin cancer. Fair skinned people, especially children, should minimise their exposure to ultraviolet radiation, and are advised to use protective measures when the UV index is forecast to reach 3 or higher. Protective measures include a combination of seeking shade, physical protection (e.g. clothing, hat, sunglasses), and applying broad-spectrum, SPF 30 + sunscreens to uncovered skin. Intentional exposure to solar ultraviolet radiation for the purpose of sunbathing and tanning is considered an unhealthy behaviour and should be avoided. Similarly, use of solaria and other artificial sources of ultraviolet radiation to encourage tanning should be strongly discouraged, through regulation if necessary. Primary prevention of skin cancer has a positive return on investment. We encourage policymakers to communicate these messages to the general public and promote their wider implementation.

From molecular basis to clinical insights: a challenging future for the vitamin D endocrine system in colorectal cancer

Colorectal cancer (CRC) is one of the most life-threatening neoplasias in terms of incidence and mortality worldwide. Vitamin D deficiency has been associated with an increased risk of CRC. 1α,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the most active vitamin D metabolite, is a pleiotropic hormone that, through its binding to a transcription factor of the nuclear receptor superfamily, is a major regulator of the human genome. 1,25(OH)2D3 acts on colon carcinoma and stromal cells and displays tumor protective actions. Here, we review the variety of molecular mechanisms underlying the effects of 1,25(OH)2D3 in CRC, which affect multiple processes that are dysregulated during tumor initiation and progression. Additionally, we discuss the epidemiological data that associate vitamin D deficiency and CRC, and the most relevant randomized controlled trials of vitamin D3 supplementation conducted in both healthy individuals and CRC patients.

Physiology of Vitamin D-Focusing on Disease Prevention

Vitamin D is a crucial micronutrient, critical to human health, and influences many physiological processes. Oral and skin-derived vitamin D is hydroxylated to form calcifediol (25(OH)D) in the liver, then to 1,25(OH)2D (calcitriol) in the kidney. Alongside the parathyroid hormone, calcitriol regulates neuro-musculoskeletal activities by tightly controlling blood-ionized calcium concentrations through intestinal calcium absorption, renal tubular reabsorption, and skeletal mineralization. Beyond its classical roles, evidence underscores the impact of vitamin D on the prevention and reduction of the severity of diverse conditions such as cardiovascular and metabolic diseases, autoimmune disorders, infection, and cancer. Peripheral target cells, like immune cells, obtain vitamin D and 25(OH)D through concentration-dependent diffusion from the circulation. Calcitriol is synthesized intracellularly in these cells from these precursors, which is crucial for their protective physiological actions. Its deficiency exacerbates inflammation, oxidative stress, and increased susceptibility to metabolic disorders and infections; deficiency also causes premature deaths. Thus, maintaining optimal serum levels above 40 ng/mL is vital for health and disease prevention. However, achieving it requires several times more than the government's recommended vitamin D doses. Despite extensive published research, recommended daily intake and therapeutic serum 25(OH)D concentrations have lagged and are outdated, preventing people from benefiting. Evidence suggests that maintaining the 25(OH)D concentrations above 40 ng/mL with a range of 40-80 ng/mL in the population is optimal for disease prevention and reducing morbidities and mortality without adverse effects. The recommendation for individuals is to maintain serum 25(OH)D concentrations above 50 ng/mL (125 nmol/L) for optimal clinical outcomes. Insights from metabolomics, transcriptomics, and epigenetics offer promise for better clinical outcomes from vitamin D sufficiency. Given its broader positive impact on human health with minimal cost and little adverse effects, proactively integrating vitamin D assessment and supplementation into clinical practice promises significant benefits, including reduced healthcare costs. This review synthesized recent novel findings related to the physiology of vitamin D that have significant implications for disease prevention.

Effect of Daily Vitamin D Supplementation on Risk of Upper Respiratory Infection in Older Adults: A Randomized Controlled Trial

BACKGROUND

Among individuals with vitamin D deficiency, daily vitamin D supplementation appears to lower risk of acute respiratory infection. However, recent trials, in different populations and using different regimens, have yielded null results. We investigated the effect of daily vitamin D supplementation (vs placebo) on risk of upper respiratory infection (URI) in older adults.

METHODS

The VITamin D and OmegA-3 TriaL (VITAL) is a randomized, double-blind, placebo-controlled trial of supplemental vitamin D and/or omega-3 fatty acids in generally healthy men (age ≥50 years) and women (age ≥55 years). This prespecified analysis focuses on vitamin D3 (2000 IU/day) versus placebo in the 15 804 (61%) participants with baseline serum total 25-hydroxyvitamin D level. The primary outcome was self-report of a recent URI at 1-year follow-up.

RESULTS

Participants had a mean age of 68 years and 51% were women; 76% were non-Hispanic White, 16% Black, and 8% other race/ethnicity. The mean 25-hydroxyvitamin D level at baseline was 31 (standard deviation, 10) ng/mL, with <12 ng/mL in 2.4%. The overall effect of vitamin D supplementation on recent URI was nonsignificant (odds ratio [OR], 0.96 [95% confidence interval {CI}, .86-1.06]). In the prespecified subgroup of primary interest (<12 ng/mL and denied taking concurrent vitamin D), which had only 255 participants, vitamin D supplementation was nonsignificant (OR, 0.60 [95% CI, .28-1.30]). Statistical power to assess effect modification in other subgroups was limited.

CONCLUSIONS

In older adults not selected for vitamin D deficiency, supplemental vitamin D did not lower URI risk overall. Whether effects differ in subgroups requires further study. Clinical Trials Registration. NCT01169259.

The Role of Vitamins in Mitigating the Effects of Various Stress Factors in Pigs Breeding

Good practices in farm animal care are crucial for upholding animal well-being, efficiency, and health. Pigs, like other farm animals, are exposed to various stressors, including environmental, nutritional, chemical, psychological, physiological, and metabolic stressors, which can disrupt their internal balance and compromise their well-being. Oxidative stress can adversely affect animal performance, fertility, and immunity, leading to economic losses for farmers. Dietary considerations are hugely important in attaining these objectives. This paper reviews studies investigating the impact of additional vitamin supplementation on stress reduction in pigs. Vitamin A can be beneficial in counteracting viral and parasitic threats. Vitamin B can be a potential solution for reproductive issues, but it might also be beneficial in reducing the effects of inappropriate nutrition. Vitamin C plays a vital role in reducing the effects of heat stress or exposure to toxins in pigs. Vitamin D proves to be beneficial in addressing stress induced mostly by infections and weaning, while vitamin E has been shown to mitigate the effects of toxins, heat stress, or transport stress. This review highlights the potential benefits of these dietary antioxidants in maintaining pig health, enhancing productivity, and counteracting the adverse effects of various stressors. Understanding the role of vitamins in pig nutrition and stress management is vital for optimising farm animal welfare and production efficiency.

Vitamin D and ischemic stroke - Association, mechanisms, and therapeutics

Confronting the rising tide of ischemic stroke and its associated mortality and morbidity with ageing, prevention and acute management of ischemic stroke is of paramount importance. Mounting observational studies have established a non-linear association of vitamin D status with cardiovascular diseases, including ischemic stroke. Paradoxically, current clinical trials fail to demonstrate the cardiovascular benefits of vitamin D supplementation. We aim to update recent clinical and experimental findings on the role of vitamin D in the disease course of ischemic stroke, from its onset, progression, recovery, to recurrence, and the established and alternative possible pathophysiological mechanisms. This review justifies the necessities to address stroke etiological subtypes and focus on vitamin D-deficient subjects for investigating the potential of vitamin D supplementation as a preventive and therapeutic approach for ischemic stroke. Well-powered clinical trials are warranted to determine the efficacy, safety, timing, target individuals, optimal dosages, and target 25OHD concentrations of vitamin D supplementation in the prevention and treatment of ischemic stroke.

The Effects of Vitamin D Supplementation on C-Reactive Protein and Systolic and Diastolic Blood Pressure in Postmenopausal Women: A Meta-Analysis and Systematic Review of Randomized Controlled Trials

BACKGROUND

An inverse relationship between vitamin D supplementation and C-reactive protein (CRP) and hypertension has been reported, mostly through observational data. This inverse relationship, however, has not been confirmed in randomized controlled trials (RCTs). A meta-analysis of RCTs is needed to provide more robust evidence.

OBJECTIVE

This systematic review of RCTs was conducted to assess the effect of vitamin D supplementation on CRP, systolic blood pressure (SBP), and diastolic blood pressure (DBP) in postmenopausal women.

METHODS

Four databases (PubMed, Web of Science, Embase, and Scopus) were systemically searched to identify relevant RCTs published in international scientific journals up to January 2023. Changes from baseline and SDs of CRP, SBP, and DBP were compared between postmenopausal women who received vitamin D supplementation and those who did not (controls). These parameters were applied to compute the overall effect sizes using the random-effects model. Data were summarized as mean difference (MD) with 95% CI. Heterogeneity among arms was scrutinized using the Cochrane's Q test and I2 statistic. Publication bias was judged by means of funnel plots and Egger's test.

RESULTS

Seven studies with 6 arms on CRP, 6 arms on SBP, and 6 arms on DBP were included in the meta-analysis. Combined effect sizes suggested a significant effect of vitamin D supplementation on CRP (MD = -0.65 mg/L; 95% CI -0.93 to -0.37 mg/L; P < .001). In addition, CRP concentrations were significantly reduced after vitamin D supplementation in studies with a duration of more than 3 months (MD = -0.91 mg/L; 95% CI -1.37 to -0.45 mg/L; P < .001) and studies involving doses of ≤1,000 IU/d (MD = -2.10 mg/L; 95% CI -2.51 to -1.68 mg/L; P < .001). Vitamin D supplementation did not reduce SBP significantly (MD = -1.06 mm Hg; 95% CI -2.43 to 0.30 mm Hg; P = .127) and DBP (MD = 0.003 mm Hg; 95% CI -0.86 to 0.86 mm Hg; P = .994) levels compared with control groups.

CONCLUSIONS

This meta-analysis concluded that vitamin D supplementation is associated with reduced CRP concentrations among postmenopausal women.

Chronotherapeutic Approaches

The chapter provides a comprehensive review of current approaches to personalized chronodiagnosis and chronotherapy. We discuss circadian clock drug targets that aim to affect cellular clock machinery, circadian mechanisms of pharmacokinetics/pharmacodynamics, and chronotherapeutic approaches aimed at increasing treatment efficacy and minimizing its side effects. We explore how chronotherapy can combat acquired and compensatory drug resistance. Non-pharmacological interventions for clock preservation and enhancement are also overviewed, including light treatment, melatonin, sleep scheduling, time-restricted feeding, physical activity, and exercise.

The Potential Use of Vitamin D3 and Phytochemicals for Their Anti-Ageing Effects

Unlike other vitamins, vitamin D3 is synthesised in skin cells in the body. Vitamin D3 has been known as a bone-related hormone. Recently, however, it has been considered as an immune vitamin. Vitamin D3 deficiency influences the onset of a variety of diseases. Vitamin D3 regulates the production of proinflammatory cytokines such as tumour necrosis factor-α (TNF-α) through binding to vitamin D receptors (VDRs) in immune cells. Since blood levels of vitamin D3 (25-OH-D3) were low in coronavirus disease 2019 (COVID-19) patients, there has been growing interest in the importance of vitamin D3 to maintaining a healthy condition. On the other hand, phytochemicals are compounds derived from plants with over 7000 varieties and have various biological activities. They mainly have health-promoting effects and are classified as terpenoids, carotenoids, flavonoids, etc. Flavonoids are known as the anti-inflammatory compounds that control TNF-α production. Chronic inflammation is induced by the continuous production of TNF-α and is the fundamental cause of diseases like obesity, dyslipidaemia, diabetes, heart and brain diseases, autoimmune diseases, Alzheimer's disease, and cancer. In addition, the ageing process is induced by chronic inflammation. This review explains the cooperative effects of vitamin D3 and phytochemicals in the suppression of inflammatory responses, how it balances the natural immune response, and its link to anti-ageing effects. In addition, vitamin D3 and phytochemicals synergistically contribute to anti-ageing by working with ageing-related genes. Furthermore, prevention of ageing processes induced by the chronic inflammation requires the maintenance of healthy gut microbiota, which is related to daily dietary habits. In this regard, supplementation of vitamin D3 and phytochemicals plays an important role. Recently, the association of the prevention of the non-disease condition called "ME-BYO" with the maintenance of a healthy condition has been an attractive regimen, and the anti-ageing effect discussed here is important for a healthy and long life.

Results of longitudinal Nutri-D study: factors influencing winter and summer vitamin D status in a Caucasian population

Introduction

Inadequate vitamin D status is a worldwide public health issue. In humans, vitamin D status is affected by diet, and even more by exposure to ultraviolet B (UVB) light and consequential endogenous synthesis. Various personal and environmental factors influence endogenous synthesis. Factors affecting vitamin D status were investigated in a prospective longitudinal cohort study with a summer and winter observation period.

Methods

The final sample included 292 adults, of those 111 (38%) males and 181 (62%) females, with a mean age of 38.2 (±11.8) years from Slovenia who were not supplementing vitamin D. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured in both periods; vitamin D intake, self-reported body mass index (BMI), and protective behaviors against sun were also recorded. Other measured parameters included measurements of constitutive skin color using the objective individual typology angle (ITA), and difference in the melanin index (ΔMI) for assessment of objective sun exposure.

Results

In winter a high prevalence (63.4%) of insufficient vitamin D status (< 50 nmoL/L) was observed with higher odds ratios (OR) for insufficiency in those with a higher BMI and light ITA. During summer, insufficiency prevalence was low (5.5%), but half of the participants (50.0%) had suboptimal 25(OH)D concentration (< 75 nmol/L). In summer OR for suboptimal status were higher in those with obesity, lower ΔMI, light ITA, low vitamin D intake, and protective clothing behaviors.

Conclusion

Using a series of measures, we showed that vitamin D status is hugely affected by several personal factors such as BMI, ITA, vitamin D intake, ΔMI, and protective behavior against the sun. This conclusion questions the usefulness of generalized population-level recommendations since personal factors are a major predictor of vitamin D status.

Vitamin D - a scoping review for Nordic nutrition recommendations 2023

Vitamin D is an essential nutrient. Its role in calcium and phosphorous metabolism, and in the development and maintenance of a healthy skeleton is well documented. In addition, there is some evidence for vitamin D decreasing total mortality and cancer mortality modestly, but not cancer incidence. Vitamin D is unique, as both diet and sun induced production in skin are sources to this vitamin. Individual vitamin D status is thus a sum of both sun exposure and dietary intakes. The discovery of vitamin D receptors and the activation of biological active vitamin D in numerous tissues and organs in the body has given support to hypothesis on vitamin D having extra-skeletal functions. The scientific literature on vitamin D and several health outcomes is high in numbers and has been increasing exponentially the last two decades. However, despite this large body of scientific publications and improvement in study quality, vitamin D supplementation has not shown to give additional health benefits when status is in sufficient range (i.e. circulating 25 hydroxyvitamin D >50 nmol/L). Well-designed studies on insufficient or deficient individuals are lacking. The totality of evidence does not support that increased intake of vitamin D beyond current recommendation will have additional beneficial health effects.

Impact of ultraviolet radiation on cardiovascular and metabolic disorders: The role of nitric oxide and vitamin D

BACKGROUND/PURPOSE

Ultraviolet (UV) radiation has both harmful and beneficial effects on human skin and health. It causes skin damage, aging, and cancer; however, it is also a primary source of vitamin D. Additionally, UV radiation can impact energy metabolism and has protective effects on several cardiovascular and metabolic disorders in mice and humans. However, the mechanisms of UV protection against these diseases have not been clearly identified.

METHODS

This review summarizes the systemic effects of UV radiation on hypertension and several metabolic diseases such as obesity, diabetes, and nonalcoholic fatty liver disease (NAFLD) in mice, and we also consider the mechanisms of action of the related regulators nitric oxide (NO) and vitamin D.

RESULTS

UV exposure can lower blood pressure and prevent the development of cardiovascular diseases and metabolic disorders, such as metabolic syndrome, obesity, and type 2 diabetes, primarily through mechanisms that depend on UV-induced NO. UV radiation may also effectively delay the onset of type 1 diabetes through mechanisms that rely on UV-induced vitamin D. UV-induced NO and vitamin D play roles in preventing and slowing the progression of NAFLD.

CONCLUSION

UV exposure is a promising nonpharmacological intervention for cardiovascular and metabolic disorders. NO and vitamin D may play a crucial role in mediating these effects. However, further investigations are required to elucidate the exact mechanisms and determine the optimal dosage and exposure duration of UV radiation.

Variation in vitamin D status in infants and children: a two-year cross-sectional study in Shanghai, China

BACKGROUND

Vitamin D deficiency (VDD) is a public health problem. The variation in vitamin D status across regions and populations remains unclear, and there is a lack of consensus regarding the screening for VDD in individuals.

METHODS

Children who visited the hospital from January 2019 to December 2020 were included in this study. Serum 25-hydroxyvitamin D (25(OH)D) concentrations were measured using an enzyme-linked immunosorbent assay. The cutoffs for serum 25(OH)D concentrations to define deficiency, insufficiency, and sufficiency were < 20 ng/mL, 20-30 ng/mL, and ≥ 30 ng/mL, respectively.

RESULTS

A total of 7285 children aged 0-11 years were assessed; the mean 25(OH)D level was 31.4 ng/mL, and the median 25(OH)D level was 30.7 (interquartile range 24.4, 37.5) ng/mL. The 25(OH)D level declined with age in clinical visiting children aged 0-11 years, but maintained a consistently high level in health examination children aged 4-11 years. The percentages of 25(OH)D < 20 ng/mL and 25(OH)D < 30 ng/mL were 10.0% and 43.8%, respectively. Higher percentages of VDD were found in clinical visiting children than in health examination children within the 6-11-year group (53.3% vs. 14.7%) and winter (44.3% vs. 15.4%).

CONCLUSION

Low vitamin D status (deficiency and insufficiency) was more common in clinic-visiting children than in health examinations, especially in schoolchildren and in the winter. The study implies the positive effects of vitamin D assessments included in child health checkups to optimize vitamin D status.

Genetic determinants of Vitamin D deficiency in the Middle Eastern Qatari population: a genome-wide association study

Introduction

Epidemiological studies have consistently revealed that Vitamin D deficiency is most prevalent in Middle Eastern countries. However, research on the impact of genetic loci and polygenic models related to Vitamin D has primarily focused on European populations.

Methods

We conducted the first genome-wide association study to identify genetic determinants of Vitamin D levels in Middle Easterners using a whole genome sequencing approach in 6,047 subjects from the Qatar Biobank (QBB) project. We performed a GWAS meta-analysis, combining the QBB cohort with recent European GWAS data from the UK Biobank (involving 345,923 individuals). Additionally, we evaluated the performance of European-derived polygenic risk scores using UK Biobank data in the QBB cohort.

Results

Our study identified an association between a variant in a known locus for the group-specific component gene (GC), specifically rs2298850 (p-value = 1.71 × 10-08, Beta = -0.1285), and Vitamin D levels. Furthermore, our GWAS meta-analysis identified two novel variants at a known locus on chromosome 11, rs67609747 and rs1945603, that reached the GWAS significance threshold. Notably, we observed a moderately high heritability of Vitamin D, estimated at 18%, compared to Europeans. Despite the lower predictive performance of Vitamin D levels in Qataris compared to Europeans, the European-derived polygenic risk scores exhibited significant links to Vitamin D deficiency risk within the QBB cohort.

Conclusion

This novel study reveals the genetic architecture contributing to Vitamin D deficiency in the Qatari population, emphasizing the genetic heterogeneity across different populations.

Association of serum vitamin D concentration with the final course of hospitalization in patients with COVID-19

Background

Vitamin D deficiency is a substantial public health problem. The present study evaluated the association between vitamin D concentration and hospitalization and mortality risk in patients with coronavirus disease 19 (COVID-19).

Methods

This study used the COronavirus in LOwer Silesia (COLOS) dataset collected between February 2020 and June 2021. The medical records of 474 patients with confirmed severe acute respiratory syndrome 2 (SARS-CoV-2) infection, and whose vitamin D concentration was measured, were analyzed.

Results

We determined a significant difference in vitamin D concentration between discharged patients and those who died during hospitalization (p = 0.0096). We also found an effect of vitamin D concentration on the risk of death in patients hospitalized due to COVID-19. As vitamin D concentration increased, the odds ratio (OR) for death slightly decreased (OR = 0.978; 95% confidence interval [CI] = 0.540-0.669). The vitamin D concentration cutoff point was 15.40 ng/ml. In addition, patients with COVID-19 and serum 25-hydroxyvitamin D (25(OH)D) concentrations < 30 ng/ml had a lower survival rate than those with serum 25(OH)D ≥ 30 ng/ml (log-rank test p = 0.0018). Moreover, a Cox regression model showed that patients with an estimated glomerular filtration rate (eGFR) ≥ 60 ml/min/1.73 m2 and higher vitamin D concentrations had a 2.8% reduced risk of mortality (hazard ratio HR = 0.972; CI = 0.95-0,99; p = 0.0097).

Conclusions

The results indicate an association between 25(OH)D levels in patients with COVID-19 and the final course of hospitalization and risk of death.

Associations of 25-hydroxyvitamin D status and vitamin D supplementation use with mortality due to 18 frequent cancer types in the UK Biobank cohort

BACKGROUND

Although the associations of serum 25-hydroxyvitamin D (25(OH)D) levels and vitamin D supplementation with total cancer mortality are well-known, evidence regarding the association of 25(OH)D and cancer site-specific mortality is predominantly limited to common cancer types, and most studies on vitamin D supplementation use have limitations on sample size and the adjustment of important confounding factors.

METHODS

We used cause-specific Cox regression models adjusted for 48 covariates to assess the associations of vitamin D deficiency, insufficiency, and vitamin D supplementation use with mortality from any cancer and 18 specific cancers in 411,436 United Kingdom Biobank participants, aged 40-69 years.

RESULTS

The majority of the study population had either vitamin D deficiency (21.1%) or insufficiency (34.4%). Furthermore, 4.1% and 20.3% of the participants regularly took vitamin D or multivitamin supplements, respectively. During a median follow-up of 12.7 years, vitamin D deficiency was associated with significantly increased mortality from total cancer and four specific cancers: stomach (hazard ratio, 95% confidence interval: 1.42, 1.05-1.92), colorectal (1.27, 1.07-1.50), lung (1.24, 1.10-1.40), and prostate (1.36, 1.06-1.75). Vitamin D insufficiency was associated with increased colorectal (1.14, 1.00-1.30) and lung cancer mortality (1.19, 1.08-1.32). Compared to non-users, vitamin D use was associated with lower lung cancer (0.75, 0.60-0.95) and total cancer mortality. Multivitamin use was associated with lower mortality from melanoma (0.64, 0.43-0.97).

CONCLUSION

Vitamin D deficiency and insufficiency were associated with increased mortality from multiple common cancers. The potential to reduce cancer mortality by vitamin D supplementation in populations with low 25(OH)D levels should be further explored.

The Genetic Architecture of Vitamin D Deficiency among an Elderly Lebanese Middle Eastern Population: An Exome-Wide Association Study

The Middle East region experiences a high prevalence of vitamin D deficiency, yet most genetic studies on vitamin D have focused on European populations. Furthermore, there is a lack of research on the genomic risk factors affecting elderly people, who are more susceptible to health burdens. We investigated the genetic determinants of 25-hydroxyvitamin D concentrations in elderly Lebanese individuals (n = 199) through a whole-exome-based genome-wide association study. Novel genomic loci displaying suggestive evidence of association with 25-hydroxyvitamin D levels were identified in our study, including rs141064014 in the MGAM (p-value of 4.40 × 10^-6) and rs7036592 in PHF2 (p-value of 8.43 × 10^-6). A meta-analysis of the Lebanese data and the largest European genome-wide association study confirmed consistency replication of numerous variants, including rs2725405 in SLC38A10 (p-value of 3.73 × 10^-8). Although the polygenic risk score model derived from European populations exhibited lower performance than European estimations, it still effectively predicted vitamin D deficiency among our cohort. Our discoveries offer novel perspectives on the genetic mechanisms underlying vitamin D deficiency among elderly Middle Eastern populations, facilitating the development of personalized approaches for more effective management of vitamin D deficiency. Additionally, we demonstrated that whole-exome-based genome-wide association study is an effective method for identifying genetic components associated with phenotypes.

Association between serum 25(OH)D and risk of all-cause mortality in adults with prior cardiovascular disease: a cohort study from NHANES 2007-2018

BACKGROUND

Serum vitamin D deficiency is common in the patients with cardiovascular disease (CVD), but the association between serum vitamin D levels and risk of all-cause mortality in patients with CVD is controversial.

OBJECTIVE

This study aimed to understand better the association between serum 25(OH)D status and risk of all-cause mortality in patients with prior CVD.

METHOD

We conducted a cohort study using data from the National Health and Nutrition Examination Survey from 2007 to 2018 to investigate the association between serum 25(OH)D and the risk of all-cause mortality using multivariate Cox regression models, with further subgroup analyses and interactions smooth curve fitting to address possible nonlinearities.

RESULT

A total of 3220 participants with prior CVD were included in this study, with a total of 930 deaths over a median follow-up of 5.52 years, with multivariable-adjusted serum vitamin D levels after natural log transformation (4.31-4.5 ) as a reference in COX regression, and corrected HRs and 95% CIs of 1.81 (1.31, 2.50), 1.34 (1.07, 1.66), 1.28 (1.05, 1.56),1.00 (reference), 1.10 (0.89, 1.37) for all-cause mortality, respectively. Results remained robust in the stratified analysis of interactions, but a L-shaped relationship was detected. We identified an inflection point of 4.5 after multivariate adjustment through a two-stage linear regression model and recursive algorithm.

CONCLUSION

Our findings demonstrate that increasing serum 25(OH)D levels may have a L-shaped relationship with risk of all-cause mortality and that increases in serum 25(OH)D levels do not continue to reduce the risk of all-cause mortality.

A Scoping Review of Vitamin D for Nonskeletal Health: A Framework for Evidence-based Clinical Practice

BACKGROUND

Low serum 25-hydroxy-vitamin D [25(OH)D] levels are prevalent worldwide. Although the benefits of vitamin D supplementation have focused on skeletal disorders (eg, rickets, osteomalacia, osteoporosis), emerging evidence for nonskeletal health merits further discussion.

PURPOSE

The purpose of this review was to critically examine the vitamin D supplementation literature pertaining to nonskeletal health to help guide clinicians.

METHODS

A scoping review that included observational studies and randomized clinical trials (RCTs) was performed. Evidence from meta-analyses and individual RCTs are discussed, and controversies and future directions are considered.

FINDINGS

25(OH)D deficiency is a ubiquitous condition associated with multiple nonskeletal diseases, including cardiometabolic (heart disease, diabetes, and kidney disease), immune (HIV/AIDS and cancer), lung (from traditional chronic disorders to coronavirus disease 2019), and gut diseases. Vitamin D deficiency also affects health across the life span (children, pregnant, and elderly), mental illness, and reproduction in both men and women. In contrast, vitamin D supplementation does not necessarily improve major medical outcomes, even when low 25(OH)D levels are treated. Screening for 25(OH)D status remains an important practice, primarily for high-risk patients (eg, elderly, women with osteoporosis, people with low exposure to sunlight). It is reasonable to supplement with vitamin D to treat 25(OH)D deficiency, such that if beneficial nonskeletal health occurs, this may be considered as a coadjutant instead of the central tenet of the disease. Furthermore, optimizing dosing regimens is an important clinical consideration.

IMPLICATIONS

Although 25(OH)D deficiency is prevalent in nonskeletal diseases, there is no uniform evidence that vitamin D supplementation improves major medical outcomes, even when low 25(OH)D levels are corrected. Findings from RCTs warrant caution due to possible selection bias. Overall, vitamin D supplementation must be guided by circulating levels as a reasonable medical practice to correct 25(OH)D deficiency.

The Role of Diet and Specific Nutrients during the COVID-19 Pandemic: What Have We Learned over the Last Three Years?

Nutrients and diets have an important impact on our immune system and infection risk and a huge number of papers have been published dealing with various aspects of nutrition in relation to SARS-CoV-2 infection risk or COVID-19 severity. This narrative review aims to give an update on this association and tries to summarize some of the most important findings after three years of pandemic. The analysis of major studies and systematic reviews leads to the conclusion that a healthy plant-based diet reduces the risks for SARS-CoV-2 infection and especially COVID-19 severity. Regarding micronutrients, vitamin D is to the fore, but also zinc, vitamin C and, to some extent, selenium may play a role in COVID-19. Furthermore, omega-3-fatty acids with their anti-inflammatory effects also deserve attention. Therefore, a major aim of societal nutritional efforts in future should be to foster a high quality plant-based diet, which not only exerts beneficial effects on the immune system but also reduces the risk for non-communicable diseases such as type 2 diabetes or obesity which are also primary risk factors for worse COVID-19 outcomes. Another aim should be to focus on a good supply of critical immune-effective nutrients, such as vitamin D and zinc.

The Impact of Vitamin D Levels on Clinical Manifestations of Multisystem Inflammatory Syndrome in Children: A Cross-Sectional Study

BACKGROUND

Hyperinflammatory response that resembles Kawasaki disease may develop in children after COVID-19 disease, and it is called multisystem inflammatory syndrome in children. The cause of MIS-C is dysregulated innate immune response and a subsequent cytokine storm that results in endothelial damage. It has been determined that low levels of serum 25(OH)D increase the risk of developing immune-related diseases and disorders.

METHODS

To determine the incidence of hypovitaminosis D, and a possible correlation between 25(OH)D levels and the clinical severity of MIS-C, 21 patients hospitalized in the University Hospital of Split due to MIS-C were evaluated.

RESULTS

Hypovitaminosis D was detected in 95% of MIS-C patients. We found a significant relationship between the severity of MIS-C and 25(OH)D levels, as patients with more severe MIS-C had lower 25(OH)D. MIS-C patients with lower vitamin D levels had worse systolic and diastolic function of the left ventricle according to echocardiograms. There was no relationship between 25(OH)D levels and the tested laboratory inflammatory and cardiac markers.

CONCLUSION

Hypovitaminosis D is very common in children with MIS-C and influences the severity of the disease. VD could be a new potential biomarker in MIS-C, and VD replacement therapy should be considered early on in the treatment of MIS-C.

Real-world evidence for the effectiveness of vitamin D supplementation in reduction of total and cause-specific mortality

BACKGROUND

Meta-analyses of randomized controlled trials (RCTs) have demonstrated the efficacy of vitamin D supplementation for reduced cancer mortality, all-cause mortality, and respiratory tract infections. However, whether and to what extent this translates into effectiveness in real-world practice is unknown.

METHODS

We assessed the association of vitamin D supplement use (as an over-the-counter drug or as part of a multivitamin product), vitamin D deficiency (25-hydroxyvitamin D, 25[OH]D <30 nmol/L), and insufficiency (25[OH]D 30 to <50 nmol/L) with all-cause and cause-specific mortality in 445,601 participants, aged 40-73 years, from the UK Biobank cohort.

RESULTS

A total of 4.3% and a further 20.4% of the study participants reported regularly taking vitamin D or multivitamin supplements, respectively. Still, the majority had either vitamin D deficiency (21.0%) or insufficiency (34.3%). We detected 49 independent determinants of vitamin D deficiency and vitamin D supplement use and used them to adjust Cox regression models for all mortality outcomes. A total of 29,107 (6.5%) participants died during a median follow-up time of 11.8 years. Both vitamin D deficiency and insufficiency were strongly associated with all mortality outcomes. Self-reported vitamin D supplement use (83% over-the-counter/17% prescription drugs) and multivitamin intake were significantly associated with 10% and 5% lower all-cause mortality, respectively. Furthermore, regular vitamin D supplement users had 11%, 11%, and 29% lower cancer, cardiovascular disease, and respiratory disease mortality than nonusers, respectively (not significant for cardiovascular disease mortality).

CONCLUSION

This large study suggests that in the real world, the efficacy of vitamin D supplements in reducing mortality may be at least as good as observed in RCTs.

Vitamin D deficiency and C-reactive protein: a bidirectional Mendelian randomization study

BACKGROUND

Low vitamin D status is often associated with systemic low-grade inflammation as reflected by elevated C-reactive protein (CRP) levels. We investigated the causality and direction of the association between vitamin D status and CRP using linear and non-linear Mendelian randomization (MR) analyses.

METHODS

MR analyses were conducted using data from 294 970 unrelated participants of White-British ancestry from the UK Biobank. Serum 25-hydroxyvitamin D [25(OH)D] and CRP concentrations were instrumented using 35 and 46 genome-wide significant variants, respectively.

RESULTS

In non-linear MR analysis, genetically predicted serum 25(OH)D had an L-shaped association with serum CRP, where CRP levels decreased sharply with increasing 25(OH)D concentration for participants within the deficiency range (<25 nmol/L) and levelled off at ∼50 nmol/L of 25(OH)D (Pnon-linear = 1.49E-4). Analyses using several pleiotropy-robust methods provided consistent results in stratified MR analyses, confirming the inverse association between 25(OH)D and CRP in the deficiency range (P = 1.10E-05) but not with higher concentrations. Neither linear or non-linear MR analysis supported a causal effect of serum CRP level on 25(OH)D concentration (Plinear = 0.32 and Pnon-linear = 0.76).

CONCLUSION

The observed association between 25(OH)D and CRP is likely to be caused by vitamin D deficiency. Correction of low vitamin D status may reduce chronic inflammation.

Prevention of Metabolic Syndrome by Phytochemicals and Vitamin D

In recent years, attention has focused on the roles of phytochemicals in fruits and vegetables in maintaining and improving the intestinal environment and preventing metabolic syndrome. A high-fat and high-sugar diet, lack of exercise, and excess energy accumulation in the body can cause metabolic syndrome and induce obesity, diabetes, and disorders of the circulatory system and liver. Therefore, the prevention of metabolic syndrome is important. The current review shows that the simultaneous intake of phytochemicals contained in citruses and grapes together with vitamin D improves the state of gut microbiota and immunity, preventing metabolic syndrome and related diseases. Phytochemicals contained in citruses include polyphenols such as hesperidin, rutin, and naringin; those in grapes include quercetin, procyanidin, and oleanolic acid. The intake of these phytochemicals and vitamin D, along with prebiotics and probiotics, nurture good gut microbiota. In general, Firmicutes are obese-prone gut microbiota and Bacteroidetes are lean-prone gut microbiota; good gut microbiota nurture regulatory T cells, which suppress inflammatory responses and upregulate immunity. Maintaining good gut microbiota suppresses TNF-α, an inflammatory cytokine that is also considered to be a pathogenic contributor adipokine, and prevents chronic inflammation, thereby helping to prevent metabolic syndrome. Maintaining good gut microbiota also enhances adiponectin, a protector adipokine that prevents metabolic syndrome. For the prevention of metabolic syndrome and the reduction of various disease risks, the intake of phytochemicals and vitamin D will be important for human health in the future.

Effects of obesity with reduced 25(OH)D levels on bone health in elderly Chinese people: a nationwide cross-sectional study

Background

Obesity is often accompanied by lower 25(OH)D levels, whereas these two parameters exhibit opposite effects on bone health. It is uncertain what are the effects of lower 25(OH)D levels in obesity on bone health in elderly Chinese people.

Methods

A nationally representative cross-sectional analysis of China Community-based Cohort of Osteoporosis (CCCO) was performed from 2016 to 2021, which consisted of 22,081 participants. Demographic data, disease history, Body mass index (BMI), bone mineral density (BMD), the levels of the biomarkers of vitamin D status and those of bone metabolism markers were measured for all participants (N = 22,081). The genes (rs12785878, rs10741657, rs4588, rs7041, rs2282679 and rs6013897) related to 25(OH)D transportation and metabolism were performed in a selected subgroup (N = 6008).

Results

Obese subjects exhibited lower 25(OH)D levels (p < 0.05) and higher BMD (p < 0.001) compared with those of normal subjects following adjustment. The genotypes and allele frequency of rs12785878, rs10741657, rs6013897, rs2282679, rs4588 and rs7041 indicated no significant differences among three BMI groups following correction by the Bonferroni's method (p > 0.05). The levels of total 25(OH)D (ToVD) were significantly different among the GC1F, GC1S and GC2 haplotype groups (p < 0.05). Correlation analysis indicated that ToVD levels were significantly correlated with parathyroid hormone levels, BMD, risk of osteoporosis (OP) and the concentration levels of other bone metabolism markers (p < 0.05). Generalized varying coefficient models demonstrated that the increasing BMI, ToVD levels and their interactions were positively associated with BMD outcomes (p < 0.001), whereas the reduced levels of ToVD and BMI increased the risk of OP, which was noted notably for the subjects with reduced ToVD levels (less than 20.69 ng/ml) combined with decreased BMI (less than 24.05 kg/m²).

Conclusion

There was a non-linear interaction of BMI and 25(OH)D. And higher BMI accompanied by decreased 25(OH)D levels is associated with increased BMD and decreased incidence of OP, optimal ranges exist for BMI and 25(OH)D levels. The cutoff value of BMI at approximately 24.05 kg/m² combined with an approximate value of 25(OH)D at 20.69 ng/ml are beneficial for Chinese elderly subjects.

Oral vitamin D supplemental therapy to attain a desired serum 25-hydroxyvitamin D concentration in essential healthcare teams

BACKGROUND

The study objectives were to ascertain the efficacy of vitamin D supplementation in rapidly increasing serum vitamin D and of implementation of a hybrid (virtual and in-person) trial.

METHODS

In a randomized triple-blind controlled trial, healthcare workers were allocated to receive an oral bolus of 100,000 IU with 10,000 IU/week of vitamin D₃ or placebo. The co-primary outcomes were the change from baseline in serum 25-hydroxyvitamin D [(Δ) 25(OH)D] and proportion with vitamin D sufficiency (25(OH)D ≥ 75 nmol/L), at endpoint. Adherence to supplements and procedures as well as adverse event rates were documented.

RESULTS

Thirty-four (19 intervention, 15 control) subjects were randomized, with 28 (41%) virtual visits. After 44.78 ± 11.00 days from baseline, a significant adjusted group difference of 44.2 (34.7, 53.8) nmol/L was observed in the Δ 25(OH)D (95% CI) in favor of supplementation; 77.8% of intervention, and 13.3% of control, patients were vitamin D sufficient (OR:6.11, 95% CI:1.6, 22.9). The adherence to intervention was 94.7% in the intervention and 100% in the control groups. Irrespective of visit type, high adherence was observed in sampling procedures and completion of fortnightly online questionnaire. No adverse events attributable to vitamin D were reported.

CONCLUSION

The vitamin D supplementation rapidly and safely raised 25(OH)D levels to sufficient levels for a biological effect. Similarly high adherence to study procedures was observed with virtual and in-person participation.

TRIAL REGISTRATION

This trial was registered at https://clinicaltrials.gov on July 23, 2020 (# NCT04483635 ).

Effects of Vitamin D3 and Marine Omega-3 Fatty Acids Supplementation on Biomarkers of Systemic Inflammation: 4-Year Findings from the VITAL Randomized Trial

Background: The VITAL study was a nationwide, randomized, double-blind, placebo-controlled, 2 × 2 factorial trial of vitamin D3 (2000 IU/day) and marine n-3 FAs (1 g/day) supplements. We recently reported that vitamin D supplementation with or without omega 3 fatty acids reduced autoimmune disease by 22% in the VITAL study. Objective: To investigate the effects of vitamin D3 and/or n-3 FAs on changes in systemic inflammatory biomarkers including pro- and anti-inflammatory cytokines over a 4-year period in the VITAL sub-cohort with in-person evaluations at the Center for Clinical Investigations (CCI) in Boston. Design: Serum levels of four inflammatory biomarkers (high-sensitivity C-reactive protein [hs-CRP], interleukin-6, interleukin-10, and tumor necrosis factor-α) were measured in a total of 2713 samples from those 1054 VITAL/CCI participants (aged 64.9 ± 6.5 years, 49% female, 84% white, and 9% black) at baseline, year 2, and year 4 follow-up visits. Results: In multiple-adjusted models, vitamin D3 supplementation decreased serum hs-CRP levels by 19% at 2-year follow-up (nominal p = 0.007; p-value after multiple comparison adjustment = 0.028), but not at 4-year follow-up (nominal and adjusted p-values > 0.05). The effects of vitamin D3 on other inflammatory markers were not statistically significant either at year 2 or year 4 (all adjusted p-values > 0.05). Marine n-3 FAs were not significantly associated with changes of all the above inflammatory markers either at years 2 and 4, after multiple comparison adjustment (all p-values > 0.05). Conclusions: Vitamin D3 supplementation with or without n-3 FAs decreased hs-CRP by 19% at year 2, but not other inflammatory biomarkers at year 2 or year 4, while n-3 FAs with or without vitamin D3 did not significantly affect these biomarkers at either time point. Our findings support a potential role of vitamin D supplementation in modulating the chronic inflammatory process, systemic inflammation, and possibly autoimmune disease progression.

Sex differences in vitamin D metabolism, serum levels and action

The ubiquity of vitamin D metabolising enzymes and vitamin D receptors in mammalian organisms suggests that vitamin D has pleiotropic effects. There are quite a few studies indicating the anticancer, cardioprotective and antidiabetic effects of vitamin D; however, the best-documented actions of vitamin D are the regulation of Ca-phosphate balance and its effect on immune function.Vitamin D levels in organisms are modulated by many environmental and non-environmental factors. One potential factor that may influence vitamin D levels and effects is the sex of the individuals studied. This review focuses on the scientific evidence indicating different synthesis and metabolism of vitamin D in females and males, mainly from PubMed database sources. The article verifies the sex differences in vitamin D levels reported around the world. Moreover, the different effects of vitamin D on the musculoskeletal, cardiovascular, nervous and immune systems, as well as cancer in males and females, were discussed.Most studies addressing sex differences in vitamin D levels and effects are observational studies with conflicting results. Therefore, carefully designed clinical trials and experiments on animal models should be carried out to determine the role of non-environmental factors that may differentiate vitamin D levels in females and males.

Workplace exposure to UV radiation and strategies to minimize cancer risk

BACKGROUND

Workplace exposure to solar ultraviolet (UV) causes malignant melanoma and non-melanoma skin cancer. The evidence for beneficial effects of solar UV exposure in reducing the risks for other cancers is increasing. The intensity of UV radiation at the Earth's surface is dependent on latitude, but even in northern European countries exposure can be high enough for outdoor work to cause skin cancer.

GROWING POINTS

Awareness of the health risks and benefits of occupational solar UV exposure is poor. Actions to reduce the risk of skin cancer have been identified and employers should recognize their responsibility to actively manage these risks. There is evidence for reduced risks for breast, ovarian and colorectal cancer and possibly other cancers linked to solar UV exposure.

SOURCES OF DATA

This narrative review draws on published scientific articles and material designed to assist identifying strategies to protect workers from solar UV exposure.

AREAS OF AGREEMENT

Solar UV exposure can be harmful. Wavelengths in the UVB range are more effective in causing erythema and DNA damage. Solar UV is the main source of vitamin D for most people. Primary and secondary prevention for skin cancer can potentially eliminate these risks but the evidence for effectiveness is limited.

AREAS OF CONTROVERSY

Potential health benefits of UV exposure, particularly for reduced cancer risk. Determining and communicating optimal exposure to maximize health benefits. The risk of non-melanoma skin cancers may be more than doubled for some workers in temperate latitudes.

AREAS TIMELY FOR DEVELOPING RESEARCH

Exposure-response epidemiological studies; studies of the health benefits of occupational UV exposure; studies of the effectiveness of intervention strategies to prevent skin cancer. Use of low-cost UV sensors in workplaces.

Effects on Serum Inflammatory Cytokines of Cholecalciferol Supplementation in Healthy Subjects with Vitamin D Deficiency

The effects of different cholecalciferol supplementation regimens on serum inflammatory cytokines in healthy subjects with vitamin D deficiency are still lacking. This is a single-center, open-label, randomized, parallel group study involving healthy subjects deficient in vitamin D (baseline 25OHD < 20 ng/mL) receiving oral cholecalciferol with three different dosing regimens: Group A: 10,000 IU/day for 8 weeks followed by 1000 IU/day for 4 weeks; Group B: 50,000 IU/week for 12 weeks and Group C: 100,000 IU every other week for 12 weeks. IL-17A, IL-6, IL-8, IL-10, IL-23 and TNFα were measured at baseline and at week 4, 8, 12, and 16. 75 healthy subjects were enrolled (58.7% female), with an average age of 34.1 ± 10.2 years. No statistical differences were observed among groups at baseline for either IL-6, IL-17A, IL-23, IL-8 or IL-10 at any time point; TNFα was indetectable. Concerning the whole sample, the time trend analysis showed a statistically significant linear trend for decreasing values over the treatment period for IL-6 (p = 0.016) and IL-17A (p = 0.006), while no significant time trends were observed for the other teste cytokines. No significant differences were found in the serum concentrations of the tested cytokines between week 12 and week 16. In young healthy individuals deficient in vitamin D, cholecalciferol administration showed a decrease in the serum IL-6 and IL-17A concentrations, without marked differences using the three regimens.

Microbe-based therapies for colorectal cancer: Advantages and limitations

Cancer is one of the leading global causes of death in both men and women. Colorectal cancer (CRC) alone accounts for ∼10 % of total new global cases and poses an over 4% lifetime risk of developing cancer. Recent advancements in the field of biotechnology and microbiology concocted novel microbe-based therapies to treat various cancers, including CRC. Microbes have been explored for human use since centuries, especially for the treatment of various ailments. The utility of microbes in cancer therapeutics is widely explored, and various bacteria, fungi, and viruses are currently in use for the development of cancer therapeutics. The human gut hosts about 100 trillion microbes that release their metabolites in active, inactive, or dead conditions. Microbial secondary metabolites, proteins, immunotoxins, and enzymes are used to target cancer cells to induce cell cycle arrest, apoptosis, and death. Various approaches, such as dietary interventions, the use of prebiotics and probiotics, and fecal microbiota transplantation have been used to modulate the gut microbiota in order to prevent or treat CRC pathogenesis. The present review highlights the role of the gut microbiota in CRC precipitation, the potential mechanisms and use of microorganisms as CRC biomarkers, and strategies to modulate microbiota for the prevention and treatment of CRC.

Effect of food and key micronutrients on Covid-19: A review

Humanity has faced different pandemics in history. The Covid-19 pandemic has made a new course in the world caused by SARS-CoV-2 that can be transmitted to humans. Finding alternative methods to prevent and control the disease through food and some micronutrients is important. This review summarizes effect of food and key micronutrients on Covid-19. There are currently no reports of the feasibility of transmission through the food sector. However, malnutrition and deficiency of some nutrients can lead to disorders of immune system. Coronavirus may be transferred through raw and uncooked foods; more safety and preventive measures are needed. Furthermore, sufficient intake of omega-3 fatty acids, minerals and vitamins are required for proper immune system function. Therefore, a healthy diet is required for prevent Covid-19. Personal hygiene and employee awareness is the two most important features in the prevention of Covid-19. Further studies are needed to confirm these results.

A Review: Highlighting the Links between Epigenetics, COVID-19 Infection, and Vitamin D

The highly transmittable and infectious COVID-19 remains a major threat worldwide, with the elderly and comorbid individuals being the most vulnerable. While vaccines are currently available, therapeutic drugs will help ease the viral outbreak and prevent serious health outcomes. Epigenetic modifications regulate gene expression through changes in chromatin structure and have been linked to viral pathophysiology. Since epigenetic modifications contribute to the life cycle of the virus and host immune responses to infection, epigenetic drugs are promising treatment targets to ameliorate COVID-19. Deficiency of the multifunctional secosteroid hormone vitamin D is a global health threat. Vitamin D and its receptor function to regulate genes involved in immunity, apoptosis, proliferation, differentiation, and inflammation. Amassed evidence also indicates the biological relations of vitamin D with reduced disease risk, while its receptor can be modulated by epigenetic mechanisms. The immunomodulatory effects of vitamin D suggest a role for vitamin D as a COVID-19 therapeutic agent. Therefore, this review highlights the epigenetic effects on COVID-19 and vitamin D while also proposing a role for vitamin D in COVID-19 infections.

The Frequency of Vitamin D and Calcium Deficiencies Among Women of Reproductive Age in Wadi Etba, Southern Region of Libya

Background

Vitamin D (VD) is the sunshine vitamin. Its deficiency is widely spread worldwide and is implicated in various health problems that have serious financial, mental, and physical health burdens. In Libya, it also has a high incidence as many studies have been conducted on this issue, but the exact situation of VD deficiency in the southern region of Libya remains unclear.

Aim 

The aim of this study is to investigate the frequency of VD deficiency and calcium status among females of reproductive age in Wadi Etba (located in the southern region of Libya).

Material and methods

This study included 622 females aged 20-40 years attending the Rural Hospital and Private Clinics in Wadi Etba for various health issues during the last five years. The study population was further subdivided into two age groups; 20-30 years and 31-40 years. VD and calcium were measured to determine the VD status among the study population.

Results

In general, 489 females had sub-optimal VD (<30 ng/mL), representing 78.6% of the total subjects. Normal VD levels were represented only by 133 subjects (21.4%). VD deficiency was represented by 354 subjects (57%) of the total subjects. A total of 232 (37%) subjects were VD-deficient females (18.3 ± 5.5 ng/ml), 122 subjects (20%) were considered poor (severe deficient, VD <10 ng/ml) represented with a mean serum VD of 8.2 ± 0.6. Furthermore, deficiency cases dominated the older age group. Regarding calcium (Ca⁺²) levels, 31% had lower than the normal range, 68% had normal range, and only 1% showed high Ca⁺² levels. On the other hand, there was no correlation between serum levels of VD and Ca⁺² levels.

Conclusion

VD deficiency has become a widespread condition in the southern region of Libya. Therefore, we recommended making lifestyle changes, including extending the exposure time to the sunlight radiation, fortifying foods and drinks with VD, and taking supplementary doses of VD to reduce the high incidence of VD deficiency.

Metabolism of 25-Hydroxy-Vitamin D in Human Macrophages Is Highly Dependent on Macrophage Polarization

Macrophages synthesize active vitamin D (1,25-dihydroxy-vitamin D) and express the vitamin D receptor in the nucleus; however, vitamin D metabolism in relation to macrophage polarization and function is not well understood. We studied monocyte-derived macrophages (MDMs) from human buffy coats polarized into M0, M1 (LPS + IFNγ), M2a (IL4 + IL13) and M2c (IL10) macrophage subtypes stimulated with 25-hydroxy-vitamin D (1000 and 10,000 nanomolar). We measured vitamin D metabolites (25-hydroxy-vitamin D, 1,25-dihydroxy-vitamin D, 24,25-dihydroxy-vitamin D and 3-epi-25-hydroxy-vitamin D) in cell media with liquid chromatography-mass spectrometry-mass spectrometry. The mRNA expression (CYP27B1, CYP24A1 and CYP24A1-SV) was measured with qPCR. We found that reparative MDMs (M2a) had significantly more 1,25-dihydroxy-vitamin D compared to the other MDMs (M0, M1 and M2c). All MDMs were able to produce 3-epi-25-hydroxy-vitamin D, but this pathway was almost completely attenuated in inflammatory M1 MDMs. All MDM subtypes degraded vitamin D through the 24-hydroxylase pathway, although M1 MDMs mainly expressed an inactive splice variant of CYP24A1, coding the degrading enzyme. In conclusion, this study shows that vitamin D metabolism is highly dependent on macrophage polarization and that the C3-epimerase pathway for vitamin D is active in macrophages.

Comparing the Evidence from Observational Studies and Randomized Controlled Trials for Nonskeletal Health Effects of Vitamin D

Although observational studies of health outcomes generally suggest beneficial effects with, or following, higher serum 25-hydroxyvitamin D [25(OH)D] concentrations, randomized controlled trials (RCTs) have generally not supported those findings. Here we review results from observational studies and RCTs regarding how vitamin D status affects several nonskeletal health outcomes, including Alzheimer's disease and dementia, autoimmune diseases, cancers, cardiovascular disease, COVID-19, major depressive disorder, type 2 diabetes, arterial hypertension, all-cause mortality, respiratory tract infections, and pregnancy outcomes. We also consider relevant findings from ecological, Mendelian randomization, and mechanistic studies. Although clear discrepancies exist between findings of observational studies and RCTs on vitamin D and human health benefits these findings should be interpreted cautiously. Bias and confounding are seen in observational studies and vitamin D RCTs have several limitations, largely due to being designed like RCTs of therapeutic drugs, thereby neglecting vitamin D's being a nutrient with a unique metabolism that requires specific consideration in trial design. Thus, RCTs of vitamin D can fail for several reasons: few participants' having low baseline 25(OH)D concentrations, relatively small vitamin D doses, participants' having other sources of vitamin D, and results being analyzed without consideration of achieved 25(OH)D concentrations. Vitamin D status and its relevance for health outcomes can usefully be examined using Hill's criteria for causality in a biological system from results of observational and other types of studies before further RCTs are considered and those findings would be useful in developing medical and public health policy, as they were for nonsmoking policies. A promising approach for future RCT design is adjustable vitamin D supplementation based on interval serum 25(OH)D concentrations to achieve target 25(OH)D levels suggested by findings from observational studies.

Molecular mechanisms and therapeutic effects of different vitamins and minerals in COVID-19 patients

COVID-19 is a rapidly spreading disease, which has caught the world by surprise. Millions of people suffer from illness, and the mortality rates are dramatically high. Currently, there is no specific and immediate treatment for this disease. Remedies are limited to supportive regiments and few antiviral and anti-inflammatory drugs. The lack of a definite cure for COVID-19 is the reason behind its high mortality and global prevalence. COVID-19 can lead to a critical illness with severe respiratory distress and cytokine release. Increased oxidative stress and excessive production of inflammatory cytokines are vital components of severe COVID-19. Micronutrients, metalloids, and vitamins such as iron, manganese, selenium, Zinc, Copper, vitamin A, B family, and C are among the essential and trace elements that play a pivotal role in human nutrition and health. They participate in metabolic processes that lead to energy production. In addition, they support immune functions and act as antioxidants. Therefore, maintaining an optimal level of micronutrients intake, particularly those with antioxidant activities, is essential to fight against oxidative stress, modulate inflammation, and boost the immune system. Therefore, these factors could play a crucial role in COVID-19 prevention and treatment. In this review, we aimed to summarize antiviral properties of different vitamins and minerals. Moreover, we will investigate the correlation between them and their effects in COVID-19 patients.