Vitamin D₃ Supplementation Reduces the Symptoms of Upper Respiratory Tract Infection during Winter Training in Vitamin D-Insufficient Taekwondo Athletes: A Randomized Controlled Trial

Applications and Benefits of Dietary Supplements in Taekwondo: A Systematic Review

Dietary supplements are commonly employed to provide additional nutritional support for athletes. In taekwondo, there is a need for evidence-based analyses to evaluate the effects of dietary supplements on training outcomes, competitive performance, and injury recovery. Taekwondo primarily relies on oxidative metabolism, yet decisive lower-limb attacks depend on non-oxidative pathways. A comprehensive literature search was conducted in PubMed, Scopus, and Web of Science databases in November 2024, utilizing keywords including 'Dietary Supplements', 'Supplements', 'Food Supplementations', and 'Taekwondo'. Of the 203 articles identified, 26 met the inclusion criteria, collectively assessing the impact of 14 different dietary supplements. Among these studies, eight provided strong evidence that acute ingestion of 3-5 mg/kg of caffeine significantly enhanced athletes' physical performance and psychological well-being. However, the ergogenic effects of the compound Fufang Ejiaojiang, creatine, sodium bicarbonate, beetroot, vitamins, and long beans require further investigation to validate their efficacy. Additionally, dietary supplements, such as amino acids, turmeric powder, ginger, spirulina, octacosanol, nucleotides, and yogurt, can reduce fatigue, supporting injury recovery, and boosting immune function, although current evidence remains insufficient. Future research should pay closer attention to reporting adverse reactions linked to dietary supplements. Doing so would provide coaches and athletes with more reliable safety information, supporting safer choices and reducing potential health risks.

A Systematic Review Supporting the Endocrine Society Clinical Practice Guidelines on Vitamin D

CONTEXT

Low vitamin D status is common and is associated with various common medical conditions.

OBJECTIVE

To support the development of the Endocrine Society's Clinical Practice Guideline on Vitamin D for the Prevention of Disease.

METHODS

We searched multiple databases for studies that addressed 14 clinical questions prioritized by the guideline panel. Of the 14 questions, 10 clinical questions assessed the effect of vitamin D vs no vitamin D in the general population throughout the lifespan, during pregnancy, and in adults with prediabetes; 1 question assessed dosing; and 3 questions addressed screening with serum 25-hydroxyvitamin D (25[OH]D). The Grading of Recommendations Assessment, Development and Evaluation approach was used to assess certainty of evidence.

RESULTS

Electronic searches yielded 37 007 citations, from which we included 151 studies. In children and adolescents, low-certainty evidence suggested reduction in respiratory tract infections with empiric vitamin D. There was no significant effect on select outcomes in healthy adults aged 19 to 74 years with variable certainty of evidence. There was a very small reduction in mortality among adults older than 75 years with high certainty of evidence. In pregnant women, low-certainty evidence suggested possible benefit on various maternal, fetal, and neonatal outcomes. In adults with prediabetes, moderate certainty of evidence suggested reduction in the rate of progression to diabetes. Administration of high-dose intermittent vitamin D may increase falls, compared to lower-dose daily dosing. We did not identify trials on the benefits and harms of screening with serum 25(OH)D.

CONCLUSION

The evidence summarized in this systematic review addresses the benefits and harms of vitamin D for the prevention of disease. The guideline panel considered additional information about individuals' and providers' values and preferences and other important decisional and contextual factors to develop clinical recommendations.

Dietary supplements to reduce symptom severity and duration in people with SARS-CoV-2: a double-blind randomised controlled trial

BACKGROUND

COVID-19 has caused morbidity, hospitalisation and mortality worldwide. Despite effective vaccines, there is still a need for effective treatments, especially for people in the community. Dietary supplements have long been used to treat respiratory infections, and preliminary evidence indicates some may be effective in people with COVID-19. We sought to evaluate whether a combination of vitamin C, vitamin D3, vitamin K2 and zinc could improve overall health and decrease symptom burden in outpatients diagnosed with COVID-19.

METHODS

Participants were randomised to receive either vitamin C (6 g), vitamin D3 (1000 units), vitamin K2 (240 μg) and zinc acetate (75 mg) or placebo daily for 21 days and were followed for 12 weeks. An additional loading dose of 50 000 units vitamin D3 (or placebo) was given on day one. The primary outcome was participant-reported overall health using the EuroQol Visual Assessment Scale summed over 21 days. Secondary outcomes included health status, symptom severity, symptom duration, delayed return to usual health, frequency of hospitalisation and mortality.

RESULTS

90 patients (46 control, 44 treatment) were randomised. The study was stopped prematurely due to insufficient capacity for recruitment. The mean difference (control-treatment) in cumulative overall health was -37.4 (95% CI -157.2 to 82.3), p=0.53 on a scale of 0-2100. No clinically or statistically significant differences were seen in any secondary outcomes.

INTERPRETATION

In this double-blind, placebo-controlled, randomised trial of outpatients diagnosed with COVID-19, the dietary supplements vitamin C, vitamin D3, vitamin K2 and zinc acetate showed no clinically or statistically significant effects on the documented measures of health compared with a placebo when given for 21 days. Termination due to feasibility limited our ability to demonstrate the efficacy of these supplements for COVID-19. Further research is needed to determine clinical utility.

TRIAL REGISTRATION NUMBER

NCT04780061.

Examination of the Cumulative Risk Assessment and Nutritional Profiles among College Ballet Dancers

This study examined female collegiate ballet dancers' (n = 28) Female Athlete Triad (Triad) risk via the Cumulative Risk Assessment (CRA) and nutritional profiles (macro- and micronutrients; n = 26). The CRA identified Triad return to play criteria (RTP: Full Clearance, Provisional Clearance, or Restricted/Medical Disqualified) by assessing eating disorder risk, low energy availability, menstrual cycle dysfunction, and low bone mineral density. Seven-day dietary assessments identified any energy imbalances of macro- and micronutrients. Ballet dancers were identified as low, within normal, or high for each of the 19 nutrients assessed. Basic descriptive statistics assessed CRA risk classification and dietary macro- and micronutrient levels. Dancers averaged 3.5 ± 1.6 total score on the CRA. Based on these scores, the RTP outcomes revealed Full Clearance 7.1%, n = 2; Provisional Clearance 82.1%, n = 23; and Restricted/Medical Disqualification 10.7%, n = 3. Dietary reports revealed that 96.2% (n = 25) of ballet dancers were low in carbohydrates, 92.3% (n = 24) low in protein, 19.2% (n = 5) low in fat percent, 19.2% (n = 5) exceeding saturated fats, 100% (n = 26) low in Vitamin D, and 96.2% (n = 25) low in calcium. Due to the variability in individual risks and nutrient requirements, a patient-centered approach is a critical part of early prevention, evaluation, intervention, and healthcare for the Triad and nutritional-based clinical evaluations.

Influence of vitamin D supplementation on immune function of healthy aging people: A pilot randomized controlled trial

OBJECTIVES

This study aims to investigate the influence of vitamin D supplementation on immune function of healthy older adults.

MATERIALS AND METHODS

Designed as a randomized controlled trial, 21 participants (55-85 years) completed the study during May-November 2018 in Coventry, England. The participants were randomized into vitamin D or the control group, stratified by age, gender and body mass index. The vitamin D group (n = 12) took vitamin D3 tablets of 1,000 IU/day for 12 weeks plus vitamin D education leaflet, while the control group (n = 9) were only provided with the leaflet. At baseline, 6 and 12 weeks, plasma 25(OH)D levels and immunological and metabolic parameters including phagocytic activity of granulocytes and monocytes, tumor necrosis factor, interleukin 6, lymphocyte subsets and fasting blood glucose and lipid were measured. Dietary vitamin D intake was analyzed at baseline and week 12. Data were presented as mean ± SD. Two-way repeated measures ANOVA and independent t-test were used to analyze the data.

RESULTS

At baseline, 42.9% of the participants were vitamin D deficiency (25(OH)D < 25 nmol/L), only 10% achieved a level of 25(OH)D > 50 nmol/L. Overweight/obese participants (n = 9) had significantly lower mean plasma 25(OH)D concentration (22.3 ± 8.7 nmol/L) than normal weight participants (48.1 ± 34.3 nmol/L) (P = 0.043). There was a significant increase in plasma 25(OH)D concentration in vitamin D group compared with that in control group (P = 0.002) during the intervention period. The plasma 25(OH)D concentration in vitamin D group was increased at 6 weeks (from 38.4 ± 37.0 nmol/L at baseline to 51.0 ± 38.2 nmol/L) with little change observed between 6 and 12 weeks (51.8 ± 36.4 nmol/L). The plasma creatinine concentration in vitamin D group was significantly decreased compared with the control group (P = 0.036) (79.8 ± 7.0 μmol/L at baseline vs 75.1 ± 5.4 μmol/L at week 12). No significant effect of vitamin D supplementation was determined on immunological parameters.

CONCLUSION

Vitamin D deficiency is common among the aging population in the UK even during the summertime. Vitamin D supplementation at 1,000 IU/day for 12 weeks significantly increased plasma 25(OH)D concentration but showed no effect on metabolic and immunological parameters except decreased plasma creatinine.

Select Dietary Supplement Ingredients for Preserving and Protecting the Immune System in Healthy Individuals: A Systematic Review

Immune health products represent approximately 10% of all US dietary supplement sales. Claims made on products to support or boost the immune system are attractive to the otherwise healthy consumer who may or may not be experiencing certain life stressors. The purpose of this systematic review is to critically evaluate the purported benefits and/or potential harms of select dietary supplement ingredients frequently listed on the labels of products having immune health or related market claims. With a focus on resilience, research questions were related to whether dietary supplement ingredients are efficacious in preserving and protecting immune health in healthy individuals; and when faced with a stressor, whether taking a supplement prophylactically can assist in maintaining health and resisting or bouncing back more quickly. Thirty-nine randomized controlled studies involving populations including children, adults and seniors exposed to stressors, such as air travel, intense exercise, academic stress, and/or exposure to winter weather, met eligibility criteria. The studies included eight of the 27 supplement ingredients identified through a market-driven scoping review. Those ingredients used in single ingredient products were echinacea, elderberry, garlic, vitamin A, vitamin C, vitamin D, vitamin E, and zinc. Whereas some studies may point to evidence for benefit, specific gaps preclude the authors from making firm statements with regard to the overall evidence-base for these products and ingredients and in answering the research questions. As we move toward a vision of health promotion and resilience rather than a sole focus on disease prevention and treatment, further work in this area of dietary supplements is of utmost importance.

Evaluation of Serum 25(OH) Vitamin D as a Risk Factor in Adult Recurrent Tonsillitis

Background Studies have reported that the rate of upper respiratory tract infections in children and adults is inversely related to serum vitamin D levels and supplementation with vitamin D reduces the incidence of this infection. This study aimed to examine if vitamin D serum levels were a risk factor for recurrent tonsillitis among adult patients. Methods Retrospective comparative analysis was carried out on 100 patients diagnosed with recurrent tonsillitis with 100 age- and sex-matched individuals as controls between June 2016 and May 2022. Tonsillar size was assessed based on Brodsky grading system. Serum levels of 25-hydroxy (25(OH)) vitamin D, total calcium, iron, hemoglobin, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were analyzed. Results There was a statistically significant low vitamin D levels in tonsil size grades III+IV compared to grade I+II (p <0.001) among cases. There was a significantly lower serum value for 25(OH) vitamin D in the cases as compared to the control group (p <0.001). A high percentage (68%) of cases had vitamin D deficiency (<20 ng/mL) and this was statistically significant (p <0.001). There were statistically significant higher values of CRP and ESR among cases compared to the control group (p <0.001). At a cut off (≤21.2), serum vitamin D levels achieved 78% sensitivity, 65% specificity (p <0.001) to differentiate cases from controls. Following logistic regression analysis, the level of vitamin D was the only significant risk factor. Conclusion Findings from our study also suggest an association between recurrent tonsillitis among our adult cohorts and low serum 25(OH) vitamin D levels. Therefore, we opine that serum vitamin D levels should be considered in the management of adult patients with tonsillitis.

Vitamin D deficiency in athletes: Laboratory, clinical and field integration

Vitamin D deficiency is highly prevalent in athletes. Increased utilisation and storage depletion may be key contributing factor. We found a higher prevalence of vitamin D inadequacy (deficiency/ insufficiency) in power than endurance sport athletes, which may be related to vitamin D utilisation and reserve in skeletal muscles.

Competitive Golf: How Longer Courses Are Changing Athletes and Their Approach to the Game

Nutritional guidance for competitive golfers to improve performance is limited. Recommendations and study conclusions from older research used smaller golf courses compared to today and require a reevaluation of energy expenditure. This review identifies aerobic fitness, in addition to strength, as a key determinant of success. A novel nutritional approach that incorporates carbohydrate supplementation to support aerobic fitness without sacrificing the ability to build strength is presented since longer courses require more stamina. Strategies for training, competition, and recovery are outlined based on different skill levels. American College of Sports Medicine (ACSM) guidelines for carbohydrates, protein, and hydration intake are tailored specifically for competitive golf based on this approach. Putting requires precise movement and can be affected by fatigue. Nutritional studies in golf and similar sports that require focused movements are presented, exhibiting an improvement with adequate hydration and carbohydrate status and caffeine use. Competitive golf poses unique challenges to an athlete and commonly used ergogenic supplements that can improve performance in a variety of circumstances during training, competition, and while traveling are reviewed.

Dietary supplements to reduce symptom severity and duration in people with SARS-CoV-2: study protocol for a randomised, double-blind, placebo controlled clinical trial

INTRODUCTION

COVID-19 has caused morbidity, hospitalisations and deaths worldwide. Despite four approved vaccines for COVID-19 in Canada, there is still a need for effective treatments, especially for people in the community. Vaccine efficacy is not 100% and long-term efficacy is still unknown. Furthermore, there are challenges to herd immunity including vaccine hesitancy and underlying conditions preventing vaccination. We aim to explore if the nutrients vitamin C, vitamin D, vitamin K₂ and zinc are an effective treatment option for outpatients diagnosed with COVID-19. The primary outcome is the difference in participant-reported overall health; secondary outcomes include the effect on health status, symptom severity and duration, frequency and length of hospitalisations and mortality.

METHODS AND ANALYSIS

This study is a two-arm, parallel-group, double-blind, placebo-controlled, phase III randomised controlled trial. 200 patients will be recruited remotely from COVID-19 test centres in Ottawa, Canada associated with The Ottawa Hospital. Overall health will be measured using the EuroQol Visual Assessment Scale; health status will be measured using the EuroQol 5-dimension 5-level questionnaire; symptom severity and duration will be measured using an independently developed questionnaire; analyses will use an area under the curve approach and compare mean scores using unadjusted t tests. Study data will be recorded on electronic case report forms using the Research Electronic Data Capture platform. An independent data safety and monitoring board will perform ongoing review of the study for feasibility and safety.

ETHICS AND DISSEMINATION

This study has received ethical approval from the research ethics boards of the Canadian College of Naturopathic Medicine and the Ottawa Health Sciences Network, as well as regulatory approval from the Therapeutic Products Directorate and Natural and Non-Prescription Health Products Directorate of Health Canada. Results will be published in a peer-reviewed scientific journal with open access.

TRIAL REGISTRATION NUMBER

NCT04780061.

Effects of Beetroot Juice Supplementation on Cognitive Function, Aerobic and Anaerobic Performances of Trained Male Taekwondo Athletes: A Pilot Study

Studies have shown that nitrate (NO₃⁻)-rich beetroot juice (BJ) supplementation improves endurance and high-intensity intermittent exercise. The dose–response effects on taekwondo following BJ supplementation are yet to be determined. This study aimed to investigate two acute doses of 400 mg of NO₃⁻ (BJ-400) and 800 mg of NO₃⁻ (BJ-800) on taekwondo-specific performance and cognitive function tests compared with a placebo (PL) and control (CON) conditions. Eight trained male taekwondo athletes (age: 20 ± 4 years, height: 180 ± 2 cm, body mass: 64.8 ± 4.0 kg) completed four experimental trials using a randomized, double-blind placebo-controlled design: BJ-400, BJ-800, PL, and CON. Participants consumed two doses of BJ-400 and BJ-800 or nitrate-depleted PL at 2.5 h prior to performing the Multiple Frequency Speed of Kick Test (FSKT). Countermovement jump (CMJ) was performed before the (FSKT) and PSTT, whereas cognitive function was assessed (via the Stroop test) before and after supplementation and 10 min following PSTT. Blood lactate was collected before the CMJ tests immediately and 3 min after the FSKT and PSST; rating of perceived exertion (RPE) was recorded during and after both specific taekwondo tests. No significant differences (p > 0.05), with moderate and large effect sizes, between conditions were observed for PSTT and FSKT performances. In addition, blood lactate, RPE, heart rate, and CMJ height were not significantly different among conditions (p > 0.05). However, after the PSTT test, cognitive function was higher in BJ-400 compared to other treatments (p < 0.05). It was concluded that acute intake of 400 and 800 mg of NO₃⁻ rich BJ reported a moderate to large effect size in anaerobic and aerobic; however, no statistical differences were found in taekwondo-specific performance.

Influence of Vitamin D Supplementation by Simulated Sunlight or Oral D3 on Respiratory Infection during Military Training

PURPOSE

This study aimed to determine the relationship between vitamin D status and upper respiratory tract infection (URTI) of physically active men and women across seasons (study 1) and then to investigate the effects on URTI and mucosal immunity of achieving vitamin D sufficiency (25(OH)D ≥50 nmol·L-1) by a unique comparison of safe, simulated sunlight or oral D3 supplementation in winter (study 2).

METHODS

In study 1, 1644 military recruits were observed across basic military training. In study 2, a randomized controlled trial, 250 men undertaking military training received placebo, simulated sunlight (1.3× standard erythemal dose, three times per week for 4 wk and then once per week for 8 wk), or oral vitamin D3 (1000 IU·d-1 for 4 wk and then 400 IU·d-1 for 8 wk). URTI was diagnosed by a physician (study 1) and by using the Jackson common cold questionnaire (study 2). Serum 25(OH)D, salivary secretory immunoglobulin A (SIgA), and cathelicidin were assessed by liquid chromatography-mass spectrometry LC-MS/MS and enzyme-linked immunosorbent assay.

RESULTS

In study 1, only 21% of recruits were vitamin D sufficient during winter. Vitamin D-sufficient recruits were 40% less likely to suffer URTI than recruits with 25(OH)D <50 nmol·L-1 (OR = 0.6, 95% confidence interval = 0.4-0.9), an association that remained after accounting for sex and smoking. Each URTI caused, on average, three missed training days. In study 2, vitamin D supplementation strategies were similarly effective to achieve vitamin D sufficiency in almost all (≥95%). Compared with placebo, vitamin D supplementation reduced the severity of peak URTI symptoms by 15% and days with URTI by 36% (P < 0.05). These reductions were similar with both vitamin D strategies (P > 0.05). Supplementation did not affect salivary secretory immunoglobulin A or cathelicidin.

CONCLUSION

Vitamin D sufficiency reduced the URTI burden during military training.

Vitamin D Deficiency and Insufficiency Among University Students: Prevalence, Risk Factors, and the Association Between Vitamin D Deficiency and Episodes of Respiratory Tract Infections

Background

Vitamin D deficiency (VDD) and insufficiency (VDI) is a public health problem worldwide. Low blood levels of vitamin D have been associated with many illnesses, including respiratory tract infections (RTIs). This study aims to evaluate the prevalence of VDD and VDI among university students, assess the correlation with demographic and anthropometric factors, and determine the effect of VDD on the respiratory tract infection (RTI) incidence.

Methods

A cross-sectional and prospective design was used. Our sample consisted of 287 students aged 18–24 years from the University of Sharjah-UAE. Participants were tested for serum 25(hydroxyvitamin)D levels, Body mass index (BMI) was calculated, and the survey was completed. The association between VDD, VDI with the participant’s characteristics, and the incidents of RTIs were examined.

Results

VDD and VDI were highly prevalent among 85% of the students. The median serum 25(OH) D level was 15.8 ng/dl (19.5±11.6). The mean BMI was (24.32±6.3) kg/m. The results showed a significant positive correlation between VDI and VDD with gender and students who were previously diagnosed with VDD (P < 0.05); however, they were not statistically significant (P < 0.05) with other factors. The tonsillitis incidents were significantly associated with VDD (P = 0.027), while no significant correlation with other incidences of RTIs was found.

Conclusion

VDD and VDI represent a significant problem across the university students specifically with the female gender. VDD is associated with tonsillitis infection incidence. Both the health and higher education authorities’ attention is needed, exploring the causes of VDD and VDI, regular 25(OH)D serum level examination, and educational programs on VDD risks are required.

Respiratory Tract Infections and Antibiotic Resistance: A Protective Role for Vitamin D?

Upper and lower respiratory tract infections are among the most common infections globally, and in the United Kingdom, they account for about half of all oral antibiotics prescribed. Antibiotic overuse and the emergence of "superbugs" that are resistant to their effects is a global problem that is becoming a serious concern. Considering this, the potential role of immunonutrition as a "prehabilitation" in helping to tackle bacterial infections and reduce over-reliance on antibiotic usage is gaining interest. This narrative mini-review summarizes current knowledge on the roles of certain nutrients in helping to modulate immune function, with particular focus on vitamin D. Vitamin D supplementation appears to reduce the risk of acute respiratory tract infections and thus could have a valuable role to play in reducing over-reliance on antibiotics. Investment in high-quality trials is needed to further explore this field.

[Vitamin D Deficiency in Sports]

Vitamin D Deficiency in Sports Abstract. A deficiency in vitamin D is very common in the general population as well as in athletes. The aim of this overview is to assess the level of knowledge about the importance of vitamin D for athletes. A deficiency in vitamin D is present in up to 90 % of athletes. Risk groups are young athletes, female athletes, athletes with a limitation such as paraplegia, vegetarians, athletes with a resorption disorder such as celiac disease, athletes training and competing indoors (e.g. ice hockey, basketball, boxing, rhythmic gymnastics), and older athletes. Dark skin pigmentation, the use of sunscreen, the time of day of the training (early morning, late evening) and the geographical location influence the risk for a deficiency in vitamin D. Exposure to the sun and a balanced diet are often not enough to prevent a vitamin D deficiency.

Vitamin D supplementation to prevent acute respiratory infections: systematic review and meta-analysis of aggregate data from randomised controlled trials

BACKGROUND

A 2017 meta-analysis of data from 25 randomised controlled trials of vitamin D supplementation for the prevention of acute respiratory infections revealed a protective effect of the intervention. Since then, 20 new RCTs have been completed.

METHODS

Systematic review and meta-analysis of data from randomised controlled trials (RCTs) of vitamin D for ARI prevention using a random effects model. Pre-specified sub-group analyses were done to determine whether effects of vitamin D on risk of ARI varied according to baseline 25-hydroxyvitamin D (25[OH]D) concentration or dosing regimen. We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science and the ClinicalTrials.gov registry from inception to 1st May 2020. Double-blind RCTs of supplementation with vitamin D or calcidiol, of any duration, were eligible if they were approved by a Research Ethics Committee and if ARI incidence was collected prospectively and pre-specified as an efficacy outcome. Aggregate data, stratified by baseline 25(OH)D concentration, were obtained from study authors. The study was registered with PROSPERO (no. CRD42020190633).

FINDINGS

We identified 45 eligible RCTs (total 73,384 participants). Data were obtained for 46,331 (98.0%) of 47,262 participants in 42 studies, aged 0 to 95 years. For the primary comparison of vitamin D supplementation vs. placebo, the intervention reduced risk of ARI overall (Odds Ratio [OR] 0.91, 95% CI 0.84 to 0.99; P for heterogeneity 0.01). No statistically significant effect of vitamin D was seen for any of the sub-groups defined by baseline 25(OH)D concentration. However, protective effects were seen for trials in which vitamin D was given using a daily dosing regimen (OR 0.75, 95% CI 0.61 to 0.93); at daily dose equivalents of 400-1000 IU (OR 0.70, 95% CI 0.55 to 0.89); and for a duration of ≤12 months (OR 0.82, 95% CI 0.72 to 0.93). No significant interaction was seen between allocation to vitamin D vs. placebo and dose frequency, dose size, or study duration. Vitamin D did not influence the proportion of participants experiencing at least one serious adverse event (OR 0.97, 95% CI 0.86 to 1.09). Risk of bias within individual studies was assessed as being low for all but three trials. A funnel plot showed left-sided asymmetry (P=0.008, Egger's test).

INTERPRETATION

Vitamin D supplementation was safe and reduced risk of ARI, despite evidence of significant heterogeneity across trials. Protection was associated with administration of daily doses of 400-1000 IU vitamin D for up to 12 months. The relevance of these findings to COVID-19 is not known and requires investigation.

FUNDING

None.

Vitamin D Update

Purpose

The goal of this review is to provide an update in the field of vitamin D, in particular, the role of vitamin D in non-skeletal health, the complexity of providing patient guidance regarding obtaining sufficient vitamin D, and the possible involvement of vitamin D in morbidity and mortality due to SARS-CoV-2 (COVID-19).

Recent Findings

In addition to bone health, vitamin D may play a role in innate immunity, cardiovascular disease, and asthma. Although rickets is often regarded as an historical disease of the early twentieth century, it appears to be making a comeback worldwide, including “first-world” countries. Broad-spectrum sunscreens (with high UVA filters) that prevent erythema are unlikely to compromise vitamin D status in healthy populations.

Summary

New attention is now focused on the role of vitamin D in a variety of diseases, and more individualized patient recommendation schemes are being considered that take into account more realistic and achievable goals for achieving sufficient vitamin D through diet, supplements, and sun behavior.

Effects of calcitriol on oxidative burst, phagocytic function, and leukocyte cytokine production in shelter dogs

Background

The active metabolite of vitamin D, calcitriol, has been shown across many different species to augment innate immune responses and dampen aberrant proinflammatory cytokine production. Community acquired infections are common in shelters and consume limited shelter resources, impact adoption rates, and can result in unnecessary euthanasia. Prophylactic oral vitamin D supplementation decreases the incidence and severity of upper and lower respiratory tract infections in humans. Before a clinical trial investigating the clinical benefit of oral vitamin D supplementation in shelter dogs can be pursued, an in vitro study evaluating the immunomodulatory effects of calcitriol in blood from shelter dogs is warranted. Therefore, the objective of this study was to determine if incubation of whole blood obtained from apparently healthy dogs housed in a shelter for ≥7 days with calcitriol would alter granulocyte/monocyte (GM) oxidative burst and phagocytic function as well as pathogen-associated molecular pattern (PAMP)-stimulated leukocyte production of tumor necrosis factor (TNF)-α, and interleukin (IL)-6, and IL-10.

Results

Ten dogs housed in a shelter for ≥7 days were enrolled in a prospective cohort study. Whole blood from these dogs was incubated with calcitriol (10^− 7 M) or diluent (control) for 24 h. Subsequent to this incubation, phagocytosis of opsonized-Escherichia coli (E. coli) and E. coli-induced oxidative burst were evaluated via flow cytometry. In addition, leukocyte production of TNF-α, IL-6, and IL-10 were measured using a canine-specific multiplex bead assay. Calcitriol significantly decreased leukocyte TNF-α production (p = 0.009) and increased IL-10 production (p = 0.002). Tumor necrosis factor-α-to-IL-10 ratio was significantly decreased with calcitriol (p = 0.017), while IL-6 production as well as GM oxidative burst and phagocytic function were not significantly affected.

Conclusions

These data indicate that calcitriol attenuates proinflammatory immune responses without affecting GM oxidative burst or phagocytic function in vitro in whole blood obtained from apparently healthy shelter dogs.

The Role of Vitamin D in Combination Treatment for Patients With Rheumatoid Arthritis

Background: The aim of this study is to evaluate the clinical efficacy of vitamin D (VitD) supplementation in terms of response to treatment and improvement of disease activity in rheumatoid arthritis (RA). Methods: This study analyzed 1180 RA patients' records treated at Mianyang Central Hospital from February 2015 to July 2019. The patients were allocated into VitD group and control group based on their medical regimens. The outcome measures were primary efficacy, defined as treatment response-based EULAR response criteria in RA, and secondary efficacy, defined as improvement in disease activity indicators. Safety was evaluated according to the incidence of all-cause infections. Results: At month 6, the primary efficacy revealed that there were 22.8% good responders and 19.0% moderate responders in the VitD group, and 22.3% good responders and 22.3% moderate responders in the control group; there were no differences between the two groups (p = 0.754). The similar primary efficacy outcomes were observed at months 3, 12, and >12. The secondary efficacy indicated that there were no differences in most indexes between the two groups at months 1, 3, 6, 12, and >12. The subgroups (based on baseline DAS28 (CRP), glucocorticoids use and disease duration) analysis results suggested that VitD group didn't have the advantage for treating RA. The incidence of infections was similar in the two groups. Conclusion: VitD supplementation did not provide additional benefit for anti-rheumatic treatment. These data supported the need for prospective, randomized, controlled trials to evaluate the role of VitD supplementation in treating RA.

The Associations of Vitamin D Status with Athletic Performance and Blood-borne Markers in Adolescent Athletes: A Cross-Sectional Study

The purpose of this study was to examine the associations of vitamin D status with athletic performance and blood-borne markers in adolescent athletes. This cross-sectional study included forty-seven Taekwondo athletes, aged 15–18 years old. Athletic performance was assessed using maximal oxygen consumption (VO_2max), Wingate anaerobic power test, vertical jump, agility T-test, lower limb muscle strength, and fatigue resistance. Blood samples were collected to assess serum 25-hydroxyvitamin D [25(OH)D], free-testosterone, cortisol, creatine kinase, and urea. One-way ANOVAs were applied using Bonferroni adjusted alpha levels, which was 0.02 (i.e., 0.05/3). Multiple linear regressions analyses as well as Pearson and partial correlation analyses were used to examine the relationship among 25(OH)D concentration, athletic performance, and blood-borne markers. The participants 25(OH)D concentration were ranged from 16 to 73.25 nmol/L, indicating that 74.5% of the adolescent athletes have vitamin D insufficiency or deficiency. The vitamin D status did not show any significant effects on the performance factors or blood-borne markers. Serum 25(OH)D concentration was positively correlated with mean power output (r = 0.359, p < 0.05) and relative mean power output (r = 0.325, p < 0.05) after adjusting for bone age, height, weight, training experience, lean body mass, and fat mass. However, 25(OH)D concentration was not associated with other performance-related factors and blood-borne markers. In addition, multiple linear regressions analyses revealed that serum 25(OH)D concentration were not significant predictors of athletic performance in adolescent athletes. In conclusion, vitamin D status is weakly correlated with anaerobic capacity; moreover, the underlying mechanisms of how vitamin D influence anaerobic performance is unclear in the present study. Nevertheless, the importance of vitamin D on health benefits should not be underestimated, especially during growth periods.

Association of the 25(OH) vitamin D status with upper respiratory tract infections morbidity in water sports elite athletes

BACKGROUND

The aim of this study is to determine seasonal changes of total serum 25(OH) vitamin D (VD) concentration and its influence on upper respiratory tract infection (URTI) morbidity among water sports elite athletes.

METHODS

The study was planned as a prospective, non-interventional, observational study. Study participants included 40 elite athletes and 30 control individuals. Serum levels of 25(OH) VD and TNF-α, IFN-γ, IL-4 and IL-6 were detected by ELISA technique. Frequency of acute URTI in participants was determined by medical cards and self-reported questionnaire during the year.

RESULTS

VD deficiency/insufficiency dominated in both groups of elite athletes, especially in synchronized swimmers (100%) in comparison with the control individuals (63.3%) (P≤0.05). Prevalence of VD deficiency/insufficiency depends on the season, but independently on the season the highest values were observed among athletes. VD sufficiency was detected in 30% and 13.3% of the control individuals in August and February and only in 10% of swimmers in August. More than 3 episodes of URTI were detected only in elite athletes in winter-spring. The elevation of TNF-α, IL-4, IL-6 and decrease of IFN-γ levels were detected in all athletes, but they were more expressed in swimmers.

CONCLUSIONS

VD insufficiency is quite pronounced among elite athletes engaged in synchronized swimming and swimmers. It is accompanied with a decrease of IFN-γ, increase of TNF-α, IL-4 and IL-6 level, and elevation of URTI morbidity. Seasonal monitoring and correction of the VD level for normalization of cytokine profile and decrease of URTI morbidity is definitely advised.

Vitamin D and Public Health

Since the early 2000's, interest in vitamin D has grown significantly among the research, clinical and lay communities [...].