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Objectives: To assess the overall effect of vitamin D supplementation on risk of acute respiratory infection (ARI), and to identify factors modifying this effect. Design: We conducted a 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. Data Sources: MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, ClinicalTrials.gov and the International Standard RCT Number (ISRCTN) registry from inception to May 2020. Eligibility Criteria for Selecting Studies: 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. Results: We identified 40 eligible RCTs (total 30,956 participants, aged 0 to 95 years). Data were obtained for 29,841 (96.5%) of 30,909 participants in 39 studies. For the primary comparison of vitamin D supplementation vs. placebo, the intervention reduced risk of ARI overall (Odds Ratio [OR] 0.89, 95% CI 0.81 to 0.98; P for heterogeneity 0.009). 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 0.94). Vitamin D did not influence the proportion of participants experiencing at least one serious adverse event (OR 0.94, 95% CI 0.81 to 1.08). Risk of bias within individual studies was assessed as being low for all but two trials. A funnel plot showed asymmetry, suggesting that small trials showing non-protective effects of vitamin D may have been omitted from the meta-analysis. Conclusions: Vitamin D supplementation was safe and reduced risk of ARI, despite evidence of significant heterogeneity across trials. The overall effect size may have been over-estimated due to publication bias. 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.

A synthetic glycolipid N-(11-cis-octadecennoyl)-β-D-glucopyranosylamine was employed for the fabrication of organic tubular structures with a cyclic hollow cylinder 30-50 nm wide through molecular self-assembly in water. Gold or silver nanoparticles encapsulated in the hollow cylinders of the lipid nanotubes (LNTs), GNPs@LNT or SNPs@LNT, respectively, were fabricated by loading aqueous gold (GNPs) or silver nanoparticles (SNPs) into the LNT hollow cylinders using capillary force. To explore an advanced fabrication method for onedimensional organization of metals, we have removed the LNT organic shell of the GNPs@LNT or SNPs@LNT nanocomposite by firing the nanocomposite in air at 450-1000 °C. A continuous gold nanowire 20-30 nm wide was successfully obtained under the firing conditions of T ) 550-750 °C, indicating that the inner cavity of the LNT can also be used as a template for the organization of gold nanowire. On the other hand, we have found no remarkable formation of silver nanowires after the same treatment for the SNPs@LNT nanocomposite as mentioned for the GNPs@LNT. All the nanostructures have been analyzed using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis (EDXA), and selected area electron diffraction (SAED).

ObjectivesThis study aimed to assess the effect of 25-hydroxyvitamin D3 (25OHD) which is a hydroxide of vitamin D3 ingestion on upper respiratory tract infection (URTI).Design and SettingA prospective, randomized, double-blind, placebo-controlled study was performed from December 2015 to September 2016 in the Nihonbashi Egawa Clinic, Kei Medical Office TOC Building Medical Clinic, and Medical Corporation Kaiseikai Kita-Shinyokohama Medical Clinic, in Japan.ParticipantsFour hundred twenty eight participants aged 45-74 years were screened by their serum 25-hydoroxyvitamin D concentration.InterventionThe participants were randomized to either 25OHD (10 μg/day) or placebo capsule, daily, for 16 consecutive weeks.MeasurementsThe primary outcome measure was the incidence proportion of URTI, and the secondary outcome measures were the physical severity score, the quality-of-life (QOL) score, the duration of URTI, and the incidence proportion of new URTI events every four weeks. Data were collected using cold diary Wisconsin Upper Respiratory Symptom Survey-21 (WURSS-21) during the intervention.ResultsOf 428 participants screened, 252 with serum 25-hydroxyvitamn D levels were deficient or insufficient (75 nmol/L or less) were enrolled in this study. Of these, 105 placebo and 110 25OHD group subjects completed the study. For the incidence proportion of URTI, no effect of 25OHD intake was observed. On the other hand, the duration of URTI was shorter in the 25OHD (P = 0.061) compared to placebo. For the incidence proportion of URTI every four weeks, the incidence of new URTI was decreased in both groups over the time of intake. However, when the 25OHD and the placebo were compared, a decrease in the incidence proportion of URTI was seen earlier in the 25OHD. When the total physical severity score and the total QOL score during the study were assessed, they both were significantly improved in the 25OHD compared to placebo.ConclusionsThe intake of 25OHD may reduce the duration of URTI, the physical severity, and the QOL when suffering from URTI.