Prevalence of Vitamin D Inadequacy Among Chinese Postmenopausal Women: A Nationwide, Multicenter, Cross-Sectional Study

Long-term ultraviolet B irradiation at 297 nm with light-emitting diode improves bone health via vitamin D regulation

Ultraviolet radiation is the primary determinant for vitamin D synthesis. Sunlight is inefficient and poses a risk, particularly for long-term exposure. In this study, we screened the most favorable wavelength for vitamin D synthesis among four types of narrowband light-emitting diodes (LEDs) and then irradiated osteoporosis rats with the optimal wavelength for 3-12 months. The 297 nm narrowband LED was the most efficient. Long-term radiation increased vitamin D levels in all osteoporotic rats and improved bone health. No skin damage was observed during irradiation. Our findings provide an efficient and safe method of vitamin D supplementation.

Vitamin D status and its associations with bone mineral density, bone turnover markers, and parathyroid hormone in Chinese postmenopausal women with osteopenia and osteoporosis

Background

Vitamin D is a key factor in bone metabolism, yet vitamin D insufficiency and deficiency are prevalent among postmenopausal women, with potential repercussions on bone mineral density (BMD), bone turnover markers (BTMs), and parathyroid hormone (PTH). Nonetheless, the findings from existing studies exhibit inconsistency, and a notable gap exists in the availability of large-scale investigations.

Methods

In this real-world study, 8,532 postmenopausal women over 50 years old with a diagnosis of osteopenia (50.9%) and osteoporosis (49.1%) at the first visit were enrolled in this study. Serum 25(OH)D level, PTH, osteocalcin (OC) and Beta-CrossLaps of type 1 collagen containing cross-linked C-telopeptide (β-CTX), were measured. BMD at all sites, including the lumbar spine, femoral neck, and total hip were obtained by dual-energy X-ray absorptiometry (DXA). The associations of serum 25(OH)D level with BMDs and BTMs were investigated using spearman correlation analysis and analysis of general linear model adjusted by age and body mass index.

Results

The serum 25(OH)D level was 22.17 ± 9.75 ng/mL among all patients included in this study. For the osteopenia group, the serum 25(OH)D level was 22.40 ± 9.41 ng/mL, while for the osteoporosis group, it measured 21.93 ± 10.08 ng/mL. In the osteopenia group, the prevalence of vitamin D deficiency, insufficiency and sufficiency was 45.8, 34.6, and 19.6%, respectively, which was close to that of the osteoporosis group (47.4, 34.3, and 18.3%) (p = 0.202). Spearman correlation analysis unveiled negative associations between serum 25(OH)D concentrations and both BTMs and PTH within both the osteopenia and osteoporosis group. In the osteoporosis group, there were positive correlations between 25(OH)D levels and femoral neck BMD (r = 0.040, p = 0.010) and total hip BMD (r = 0.053, p = 0.001). Furthermore, we found that for the osteopenia group, greater vitamin D levels were associated with greater femoral neck BMD (p = 0.020) and total hip BMD (p = 0.008) and lower β-CTX (p < 0.001), OC (p < 0.001), and PTH (p < 0.001). The same trends were seen in osteoporosis patients (p < 0.05), and with greater lumbar spine BMD with higher levels of 25(OH)D (p = 0.009).

Conclusion

This study showed high prevalence of vitamin D deficiency and insufficiency in Chinese postmenopausal women with osteopenia and osteoporosis and the relationships between vitamin D and BMD, BTMs and PTH. The results contribute to a more comprehensive understanding of how vitamin D may impact bone health.

Geographic location and ethnicity comprehensively influenced vitamin D status in college students: a cross-section study from China

BACKGROUND

Vitamin D plays an important role in the health of adolescents, whereas vitamin D status of Chinese college students was seldom studied in China. To explore the vitamin D status and its relationship with ethnicity and geographic location in Chinese college students.

METHODS

The freshmen were taken a physical examination by trained medical personnel after they reported to university. Demographic information including age, gender, ethnicity, region of original residence was collected using a questionnaire survey. Serum 25(OH)D3 concentrations were measured using a liquid chromatograph mass spectrometer. Multiple regression analyses were used to explore the factors that influence serum 25(OH)D3 levels.

RESULTS

Totally 3220 freshmen who came from 26 provinces, autonomous districts or municipalities were recruited, with a mean age of 18.75 ± 1.18 years and 70.2% of them were female. The mean serum 25(OH)D3 levels were 18.51 ± 6.54 ng/mL, and the proportion of vitamin D deficiency (< 20 ng/mL) and insufficiency (20 ~  < 30 ng/mL) was 64.4% and 30.2%, respectively. The combined proportion of vitamin D deficiency and insufficiency was increased with the latitude increased. Miao had the highest serum 25(OH)D3 levels, whereas Kazak ethnic had the lowest (22.51 ng/mL vs. 13.94 ng/mL) among different ethnic groups. Female students, students from city, Uighur and Kazak ethnic, residing in high latitude was significantly associated with lower serum 25(OH)D3 levels (P < 0.05).

CONCLUSIONS

Vitamin D deficiency is an important health problem in Chinese college students. Sunlight activities, dietary and life-style intervention for college students according to geographic location and ethnicities should be considered.

Optimal Serum 25(OH)D Levels and Vitamin D Intake in Korean Postmenopausal Women

Vitamin D plays a crucial role in regulating the growth and maintenance of the musculoskeletal system. Postmenopausal women are vulnerable to bone fractures because of the decrease in bone mineral density (BMD). Therefore, this study aimed to identify the determinants that influence BMD and the 25(OH)D levels in Korean postmenopausal women. This study collected general and dietary intake information, measured biochemical indices, and conducted BMD tests in 96 postmenopausal women residing in a metropolitan area in Korea. This study analyzed factors that influenced serum 25-hydroxyvitamin D (25(OH)D) and BMD, as well as the correlation between the intact parathyroid hormone (iPTH) and serum 25(OH)D levels. The serum 25(OH)D levels increased by 0.226 ng/mL in the summertime, 0.314 ng/mL in the wintertime, and 0.370 ng/mL on annual average when vitamin D intake rose by 1 µg/1000 kcal. When the serum 25(OH)D levels were ≥18.9 ng/mL, the iPTH levels did not rapidly increase. To maintain the serum 25(OH)D levels at ≥18.9 ng/mL, a daily vitamin D intake of ≥13.21 µg was required. Consequently, consuming vitamin D-fortified foods or vitamin D supplements is necessary to improve both bone health and vitamin D nutritional status.

Vitamin D Status among Women of Different Asian Subgroups Initiating Osteoporosis Therapy

Among 1866 Asian women (901 Filipina women, 654 Chinese women, and 311 Japanese women) who had vitamin D assessment prior to initiation of osteoporosis therapy, Filipina women had a lower prevalence of vitamin D deficiency compared to Chinese women, despite higher body mass index. In multivariable analyses that adjusted for age, body mass index, and smoking status, the relative risk of low vitamin D was significantly higher for Chinese women (relative risk 1.4, 95% confidence interval 1.1-1.7) but not Japanese women (relative risk 1.2, 95% confidence interval 0.9-1.6). The 40% higher risk of low Vitamin D in Chinese compared to Filipina women emphasizes the importance of disaggregating Asian race when examining nutritional health attributes.

Prevalent vertebral fractures among urban-dwelling Chinese postmenopausal women: a population-based, randomized-sampling, cross-sectional study

In this population-based, cross-sectional study, we investigated vertebral fracture (VF) prevalence among Chinese postmenopausal women. We found 14.7% of population had VFs, which increased with age. Age ≥ 65 years, hip fracture, and densitometric osteoporosis were significantly associated with VFs. The prevalence of osteoporosis was remarkably high.

PURPOSE

To investigate VF prevalence among Chinese postmenopausal women in this population-based, randomized-sampling, cross-sectional study.

METHODS

The investigator obtained lists of women from communities. Randomization was performed using SAS programming based on age group in each region. Postmenopausal women aged ≥ 50 years in the urban community were included. The investigator interviewed subjects to collect self-reported data and measured BMD. Spine radiographs were adjudicated by Genant's semi-quantitative method. VFs were defined as fractures of at least one vertebra classified by Genant's score 1-3 and were analyzed using descriptive statistics.

RESULTS

A total of 31,205 women listed for randomized sampling from 10 Tier-3 hospitals at 5 regions. Of 2634 women in the full analysis set, 14.7% (388/2634, 95% CI: 13.4, 17.1) had prevalent VFs. VF prevalence increased with age (Cochran-Armitage test p < 0.0001) and was significantly higher in women aged ≥ 65. VF prevalence did not differ between North (14.4%, 95% CI: 12.5, 16.4) and South China (15.1%, 95% CI: 13.3, 17.1). In women with no prior VFs, prevalent VFs were 12.4% (95% CI: 11.2, 13.7). Age ≥ 65 years (OR: 2.57, 95% CI: 1.91, 3.48), hip fracture (OR: 2.28, 95% CI: 1.09, 4.76), and densitometric osteoporosis (OR: 2.52, 95% CI: 1.96, 3.22) were significantly associated with prevalent VFs. Prevalence of osteoporosis was 32.9% measured by BMD and 40.8% using NOF/IOF clinical diagnosis criteria.

CONCLUSION

VFs are prevalent among Chinese postmenopausal women who were ≥ 50 years and community-dwelled. Osteoporosis prevalence is remarkable when fragile fractures were part of clinical diagnosis.

Change of vitamin D status and all-cause mortality among Chinese older adults: a population-based cohort study

BACKGROUND

The association of vitamin D with all-cause mortality remains controversial and longitudinal evidence exploring the potential effects of change in vitamin D status is limited in the oldest old (aged ≥ 80 years old). We aimed to study the relationship between vitamin D change and all-cause mortality among older Chinese adults including the oldest old.

METHODS

The data of Chinese Longitudinal and Health Longevity Study in 2012 and 2014 wave was used for baseline data. Mortality was assessed in the subsequent 2018 survey waves. Cox proportional hazard regression models were used to calculate hazard ratios (HRs) and 95% confidence interval (CI) of all-cause mortality related to vitamin D change, including maintaining deficiency or no deficiency, deficiency to no deficiency, and no deficiency to deficiency, using below 50 nmol/L as definition of deficiency.

RESULTS

The mean age of the total 1362 participants was 84.4 ± 12.1(60-113) years. The prevalence of vitamin D deficiency was 67.5% and 68.4% in 2012 and 2014 wave respectively, and significantly differed by sex and age at baseline. Cox regression showed that participants with deficiency to no deficiency and maintaining no deficiency of vitamin D status had decreased HR for all-cause mortality, compared to the maintaining deficiency group. The HRs for mortality were 0.70(95%CI: 0.50-0.96, p = 0.028) and 0.47(95%CI: 0.33-0.68, p < 0.001) respectively in the adjusted model. Also, females and the oldest old had a greatest reduction in mortality risk. And no significant difference in mortality in the no deficiency to deficiency group.

CONCLUSIONS

Not only maintaining no deficiency, but also the change from deficiency to no deficiency of vitamin D status were associated with lower risk of all-cause mortality, especially in the female and oldest-old participants initially with low vitamin D level.

Nutritional perspectives for the prevention and mitigation of COVID-19

Worldwide, there is an array of clinical trials under way to evaluate treatment options against coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2. Concurrently, several nutritional therapies and alternative supportive treatments are also being used and tested to reduce the mortality associated with acute respiratory distress in patients with COVID-19. In the context of COVID-19, improved nutrition that includes micronutrient supplementation to augment the immune system has been recognized as a viable approach to both prevent and alleviate the severity of the infection. The potential role of micronutrients as immune-boosting agents is particularly relevant for low- and middle-income countries, which already have an existing high burden of undernutrition and micronutrient deficiencies. A systematic literature review was performed to identify nutritional interventions that might prevent or aid in the recovery from COVID-19. The PubMed, ScienceDirect, Cochrane, Scopus, Web of Science, and Google Scholar databases were searched electronically from February to April 2020. All abstracts and full-text articles were examined for their relevance to this review. The information gathered was collated under various categories. Deficiencies of micronutrients, especially vitamins A, B complex, C, and D, zinc, iron, and selenium, are common among vulnerable populations in general and among COVID-19 patients in particular and could plausibly increase the risk of mortality. Judicious use of need-based micronutrient supplementation, alongside existing micronutrient fortification programs, is warranted in the current global pandemic, especially in low- and middle-income economies.

Nutritional perspectives for the prevention and mitigation of COVID-19

Worldwide, there is an array of clinical trials under way to evaluate treatment options against coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2. Concurrently, several nutritional therapies and alternative supportive treatments are also being used and tested to reduce the mortality associated with acute respiratory distress in patients with COVID-19. In the context of COVID-19, improved nutrition that includes micronutrient supplementation to augment the immune system has been recognized as a viable approach to both prevent and alleviate the severity of the infection. The potential role of micronutrients as immune-boosting agents is particularly relevant for low- and middle-income countries, which already have an existing high burden of undernutrition and micronutrient deficiencies. A systematic literature review was performed to identify nutritional interventions that might prevent or aid in the recovery from COVID-19. The PubMed, ScienceDirect, Cochrane, Scopus, Web of Science, and Google Scholar databases were searched electronically from February to April 2020. All abstracts and full-text articles were examined for their relevance to this review. The information gathered was collated under various categories. Deficiencies of micronutrients, especially vitamins A, B complex, C, and D, zinc, iron, and selenium, are common among vulnerable populations in general and among COVID-19 patients in particular and could plausibly increase the risk of mortality. Judicious use of need-based micronutrient supplementation, alongside existing micronutrient fortification programs, is warranted in the current global pandemic, especially in low- and middle-income economies.

Long-Term Bioavailability of Single Doses of Intramuscular Vitamin D2

OBJECTIVE

We sought to determine the long-term bioavailability of single doses of intramuscular (IM) vita-min D₂ (D₂) in healthy adults.

METHODS

Forty healthy volunteers with hypovitaminosis D received a single dose of 200,000, 400,000, or 600,000 IU intramuscular D₂ or no treatment. Levels of 25-hydroxyvitamin D₂ (25&lsqb;OH]D₂) and 25-hydroxyvitamin D₃ (25&lsqb;OH]D₃) in serum were measured by liquid chromatography-tandem mass spectrometry. Vitamin D binding protein (DBP) and intact parathyroid hormone (iPTH), bone turnover markers (BTMs), and serum and urinary calcium were also measured.

RESULTS

After a single dose of D₂ injection, the level of 25(OH)D₂ increased slowly and reached a plateau at 8 weeks. The plateau remained stable for 12 weeks. The mean increase in 25(OH)D₂ was 6.8, 9.6, or 15.6 ng/mL after injection of 200,000 IU, 400,000 IU, or 600,000 IU D₂. Although endogenous 25(OH)D₃ levels were reduced by IM D₂, the total 25(OH)D levels increased by 5.0, 7.0, or 10.3 ng/mL in average after injection of 200,000 IU, 400,000 IU, or 600,000 IU D₂. The iPTH levels were also decreased by IM D₂. However, levels of serum calcium, BTMs, and DBP and urinary calcium were not altered by IM D₂.

CONCLUSION

A single dose of 200,000 IU, 400,000 IU, or 600,000 IU IM D₂ raises total 25-hydroxyvitamin D levels by 5.0, 7.0, or 10.3 ng/mL on average for at least 12 weeks and reduces iPTH and endogenous 25(OH)D₃ levels without affecting levels of serum calcium, BTMs, DBP, and urinary calcium.

Efficacy of denosumab co-administered with vitamin D and Ca by baseline vitamin D status

INTRODUCTION

In anti-osteoporosis drug trials, vitamin D and calcium (Ca) are common supplements; however, the optimal dose of each is unclear. Using data from the randomized, double-blind, placebo-controlled DIRECT trial, we assessed whether baseline serum 25-hydroxy vitamin D (25[OH]D) level influences the efficacy of denosumab co-administered with vitamin D and Ca.

MATERIALS AND METHODS

In this prespecified sub-analysis, subjects with primary osteoporosis who received denosumab or placebo, plus vitamin D (≥ 400 IU/day) and Ca (≥ 600 mg/day), were classified as 25(OH)D deficient (< 20 ng/mL), insufficient (≥ 20 to < 30 ng/mL), and sufficient (≥ 30 ng/mL). Study endpoints included absolute serum 25(OH)D level at baseline, 12 months, and 24 months; change in serum 25(OH)D and bone mineral density (BMD) status from baseline; and incidence of new vertebral fractures at 24 months.

RESULTS

In 475 denosumab-treated and 481 placebo-treated subjects, proportions with deficient/insufficient/sufficient 25(OH)D at baseline were 53.1%/37.1%/9.9% and 50.9%/42.0%/7.1%, respectively. Supplementation significantly increased mean serum 25(OH)D levels; at 24 months, mean levels were > 30 ng/mL (sufficient) in both treatment groups. Increase in BMD over time was higher in the denosumab group vs. placebo group in all three vitamin D status groups. At month 24, denosumab-treated subjects with deficient/insufficient baseline 25(OH)D had a significantly lower risk of new vertebral fracture vs. placebo-treated subjects.

CONCLUSION

Among DIRECT trial subjects supplemented with ≥ 400 IU/day of vitamin D and ≥ 600 mg/day of Ca, baseline 25(OH)D sufficiency may not influence the efficacy of denosumab in increasing BMD or preventing vertebral fractures.

Back to basics: review on vitamin D and respiratory viral infections including COVID-19

IMPORTANCE

As the scientific community is in a marathon in finding out the cure for COVID-19, in this crisis, it is essential for the physicians not to forget about the basics. Due to the pandemic crisis, in many nursing homes and hospitals, there established new policies on decreasing unnecessary medications to minimize cross-contamination. Sometimes these policies are making providers avoid essential drugs such as Vitamins, including Vitamin D. In this paper, we try to emphasize the importance of Vitamin D in COVID-19 and respiratory viral patients.

RELEVANCE

Vitamin D helps in decreasing the 'pro-inflammatory cytokines' in the lungs and acts in immunomodulatory function, and 'also it will increase the anti-inflammatory, antiviral responses of the respiratory epithelial cells during infection.'

CONCLUSION

Due to the highly contagious nature of COVID-19 and the increased morbidity and mortality with no appropriate therapy and vaccine, one must be cautious and do everything to help COVID-19 patients. In hospitals and other health care settings to decrease cross-contamination, holding other non-essential medications is taking place. Discontinuing Vitamins could increase the mortality and morbidity of those affected, especially in deficient/insufficient individuals. Obtaining serum 25 (OH) D levels in all patients with viral respiratory infections, especially COVID-19, could help in the detection and treatment of Vitamin D deficiency and potentially decrease recovery time and improve outcome. Even though evidence suggests that vitamin D has the anti-inflammatory, antiviral properties, randomized double-blinded controlled trials are needed to verify this further, and to understand Vitamin D and COVID-19 better.

ABBREVIATIONS

Vitamin D receptor-VDR; 25(OH)D- 25 hydroxyvitamin D; 1,25 (OH)D-1,25 dihydroxy Vitamin D; 1α,25-dihydroxy Vitamin D-1,25[OH]2 D or calcitriol; IU- International Units; Interferons stimulated genes- ISG; ARI- acute respiratory infection; RSV- respiratory syncytial virus; RTI- Respiratory tract infections; COPD-Chronic obstructive pulmonary disease; BMI-Basal metabolic index; USA-USA.

Correlation between bone turnover and metabolic markers with age and gender: a cross-sectional study of hospital information system data

BACKGROUND

Bone turnover and metabolic indicators are related to age and gender. Age and gender should be matched in subjects in disease control research of bone turnover and metabolism, but strict matching of gender and age increases the difficulty and cost of the research. Therefore, the aim of this study was to solve it is necessary to strictly match age and gender in clinical research in bone metabolism.

METHODS

A cross-sectional study was conducted from the data were extracted from the HIS of ZhuJiang Hospital. Data relating to seven bone turnover and metabolic indicators from 1036 patients between January 2018 and October 2019 were analyzed.

RESULTS

P1NP, β-CTx and 25(OH)D were significant different in individuals younger than 20 years of age. ALP was significantly higher in those under 20 years of age and lower at age 20-39 compared with other age groups. The concentrations of Ca and P were different among the groups aged 0-19, 20-39, and 40-59 years of age groups but exhibited no difference above 60 years of age. PTH expression was not dependent on age. P1NP, β-CTx and PTH concentrations were not significantly different between the genders within the same age group. ALP was significantly different between genders within the age range 20-59 years. Ca and 25(OH)D were significantly different between the genders for those older than 60. Serum P was significantly different in the two genders for those aged 40-79. Patients received both alfacalcidol and calcium treatment differently from the others in P1NP, β-CTx, Serum Ca, P and ALP.

CONCLUSION

P1NP and β-CTx were highly correlated with age. If these two indictors require analysis in a case control study, the patients and controls should be strictly matched by age under 20 years. The demarcation point for ALP was 40 years of age. Ca and P were strongly recommended strict matching according to age in disease research. The difference in P1NP, β-CTx, 25(OH)D and ALP between genders depends on age differences. Medication history should be considered in bone turnover and metabolic clinical research.

A comparative epidemiologic study of fractures among people in rural and urban areas

PURPOSE

This study aimed to comparatively analyse the epidemiologic characteristics of fractures among inpatients from rural and urban areas.

METHODS

This study retrospectively analysed patients with traumatic fractures of the limbs, pelvis and spine treated in our hospital from January 2017 to December 2017. Patients from rural and urban areas were classified into Group A and Group B, respectively. Data on age, sex, distribution of fracture locations, injury mechanism, season, date and time when the fracture occurred, length of hospital stay, chronic comorbidities and in-hospital mortality were collected, and compared between both groups.

RESULTS

A total of 10,046 patients (Group A: 4,440; 3,062 males and 1,378 females and Group B: 5,606; 3,374 males and 2,232 females) with traumatic fractures were included. The male-to-female ratio was significantly different between both groups (P<0.001). In Groups A and B, the patients aged 41.9 ± 21.6 and 45.0 ± 23.5 years old, respectively, showing significant difference (P<0.05). As for injury mechanism, the most common one was low-energy injury (Group A: 2110, accounting for 47.5%; Group B: 3422, accounting for 61.0%) in both Groups, followed by traffic accidents (Group A: 921, accounting for 20.7%; Group B: 973, accounting for 17.4%). In patients with multiple injuries, the most common mechanism of injury is traffic accidents (354, 46.1%). There were 178 patients in Group A (4.0%) and 141 patients in Group B (2.5%) combined with head injury. As for season, both groups had most of the fractures in autumn (Group A: 1449, accounting for 32.6%; Group B: 1518, accounting for 27.3%).

CONCLUSION

The epidemiological features of patients with traumatic fractures in rural and urban areas are somewhat different in terms of age distribution, injury mechanism, injured body site and season. Patients with high risk of fractures in rural areas were younger than those in urban areas. Fractures more frequently occurred in the wrist and hips in rural and urban areas, respectively. Prevention of low-energy-induced osteoporotic fractures has become very critical for both rural and urban populations. Reducing the risk of traffic accident remains critical to prevent multiple injuries.

Vitamin D: A simpler alternative to tocilizumab for trial in COVID-19?

There is anecdotal evidence that tocilizumab, an immunosuppressant drug, may be a potential therapeutic option for patients with severe manifestations of coronavirus disease 2019 (COVID-19). Like tocilizumab, Vitamin D appears to modulate the activity of an interleukin (IL-6), which may explain the seasonal variation in prevalence of influenza. While most cases of COVID-19 have, thus far, occurred in the Northern Hemisphere winter, limiting the ability to assess seasonal variation, there remains substantial variation in the severity of this condition that has yet to be explained. A retrospective comparison of Vitamin D levels in previously obtained blood samples between survivors and confirmed fatalities could establish a rationale for implementation of widespread Vitamin D supplementation. This would be far cheaper and simpler than tocilizumab as a therapeutic option to trial.

Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths

The world is in the grip of the COVID-19 pandemic. Public health measures that can reduce the risk of infection and death in addition to quarantines are desperately needed. This article reviews the roles of vitamin D in reducing the risk of respiratory tract infections, knowledge about the epidemiology of influenza and COVID-19, and how vitamin D supplementation might be a useful measure to reduce risk. Through several mechanisms, vitamin D can reduce risk of infections. Those mechanisms include inducing cathelicidins and defensins that can lower viral replication rates and reducing concentrations of pro-inflammatory cytokines that produce the inflammation that injures the lining of the lungs, leading to pneumonia, as well as increasing concentrations of anti-inflammatory cytokines. Several observational studies and clinical trials reported that vitamin D supplementation reduced the risk of influenza, whereas others did not. Evidence supporting the role of vitamin D in reducing risk of COVID-19 includes that the outbreak occurred in winter, a time when 25-hydroxyvitamin D (25(OH)D) concentrations are lowest; that the number of cases in the Southern Hemisphere near the end of summer are low; that vitamin D deficiency has been found to contribute to acute respiratory distress syndrome; and that case-fatality rates increase with age and with chronic disease comorbidity, both of which are associated with lower 25(OH)D concentration. To reduce the risk of infection, it is recommended that people at risk of influenza and/or COVID-19 consider taking 10,000 IU/d of vitamin D₃ for a few weeks to rapidly raise 25(OH)D concentrations, followed by 5000 IU/d. The goal should be to raise 25(OH)D concentrations above 40-60 ng/mL (100-150 nmol/L). For treatment of people who become infected with COVID-19, higher vitamin D₃ doses might be useful. Randomized controlled trials and large population studies should be conducted to evaluate these recommendations.

Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths

The world is in the grip of the COVID-19 pandemic. Public health measures that can reduce the risk of infection and death in addition to quarantines are desperately needed. This article reviews the roles of vitamin D in reducing the risk of respiratory tract infections, knowledge about the epidemiology of influenza and COVID-19, and how vitamin D supplementation might be a useful measure to reduce risk. Through several mechanisms, vitamin D can reduce risk of infections. Those mechanisms include inducing cathelicidins and defensins that can lower viral replication rates and reducing concentrations of pro-inflammatory cytokines that produce the inflammation that injures the lining of the lungs, leading to pneumonia, as well as increasing concentrations of anti-inflammatory cytokines. Several observational studies and clinical trials reported that vitamin D supplementation reduced the risk of influenza, whereas others did not. Evidence supporting the role of vitamin D in reducing risk of COVID-19 includes that the outbreak occurred in winter, a time when 25-hydroxyvitamin D (25(OH)D) concentrations are lowest; that the number of cases in the Southern Hemisphere near the end of summer are low; that vitamin D deficiency has been found to contribute to acute respiratory distress syndrome; and that case-fatality rates increase with age and with chronic disease comorbidity, both of which are associated with lower 25(OH)D concentration. To reduce the risk of infection, it is recommended that people at risk of influenza and/or COVID-19 consider taking 10,000 IU/d of vitamin D₃ for a few weeks to rapidly raise 25(OH)D concentrations, followed by 5000 IU/d. The goal should be to raise 25(OH)D concentrations above 40-60 ng/mL (100-150 nmol/L). For treatment of people who become infected with COVID-19, higher vitamin D₃ doses might be useful. Randomized controlled trials and large population studies should be conducted to evaluate these recommendations.