Annweiler 2020, [67]to evaluate whether bolus vitamin D supplementation taken regularly was effective in improving survival among hospitalized frail elderly COVID-19 patients in elderly vitamin D supplementation was associated with less severe COVID-19 and better survival.Adjuvant treatment for COVID-19Sulli 2021, [68]to correlate the 25OH-vitamin D serum concentrations with clinical parameters of lung involvement, in elderly patients hospitalized for SARS-CoV-2 infection25OH-vitamin D serum deficiency is associated with more severe lung involvement, longer disease duration and risk of death, in elderly COVID-19 patients.Crucial risk factor at any ageAlexander 2020, [69]to investigate the usefulness of early micronutrient intervention, focus on vitamin D, to relieve escalation of COVID-19they recomend early outpatient nutritional intervention in SARS-CoV-2 exposed or high-risk subjects.Nutritive adjuvant therapyRadujkovic 2020, [70]to explore possible associations of vitamin D status with disease severity and survivalVitamin D deficiency was associated with higher risk of invasive mechanical ventilation and death, when adjusted for age, gender, and comorbidities.High risk of potentially fatal COVID-19Sarhan 2022, [71] to explore the effect of high-dose intramuscular vitamin D in hospitalized adults infected with moderate-to-severe SARS-CoV-2 in comparison with the standard of care in the COVID-19 protocol.study showed that high-dose vitamin D was considered a promising treatment in the suppression of cytokine storms among COVID-19 patients and was associated with better clinical improvement and fewer adverse outcomes compared to low-dose vitamin D.Cytokine response against infections in the era of COVID-19Pizzini 2020, [72]to investigate associations of vitamin D status to disease presentation within the COVID-19 registryVitamin D deficiency is frequent among COVID-19 patients but not associated with disease outcomes.Disturbed parathyroid-vitamin-D axisHastie 2021, [73]to establish whether baseline serum 25(OH)D concentration was associated with COVID-19 mortality, and inpatient confirmed COVID-19 infection, in UK Biobank participantsnot a potential link between 25(OH)D concentrations and risk of severe COVID-19 infection and mortality.25(OH)D and confirmed COVID-19 infection or mortalitySabico 2021, [74]to determine the effects of 5000 IU versus 1000 IU daily oral vitamin D supplementation in the recovery of symptoms and other clinical parameters among mild to moderate COVID-19 patients with sub-optimal vitamin D statusa 5000 IU daily oral vitamin D3 supplementation for 2 weeks reduces the time to recovery for cough and gustatory sensory loss among patients with sub-optimal vitamin D status and mild to moderate COVID-19 symptoms.Vitamin D supplementation among those with suboptimal levels against COVID-19Gönen 2021, [75]to establish an acute treatment protocol to increase serum vitamin D, evaluate the effectiveness of vitamin D3 supplementation, and reveal the potential mechanisms in COVID-19Vitamin D treatment shortened hospital stay and decreased mortality in COVID-19 cases.Vitamin D supplementation is effective on various targeted parametersRustecka 2021, [76] to evaluate whether home confinement led to decreased vitamin D serum levels in children in Warsaw, Poland.The COVID-19 pandemic restrictions led to a significant decrease in vitamin D serum levels in children.The importance of vitamin D supplementation in the paediatric populationBoulkrane 2020, [61]To establish the potential role of vitamin D in SARS-CoV-2 virus/COVID-19 diseaseThe higher concentrations of vitamin D3 is better for the protection from various viral and respiratory infections.Supplementation of vitamin D3 in COVID-19 Bishop 2020, [77]To provide an update on current understanding of the prominent immune actions of vitamin D, as well as highlighting new, less well-recognized immune effects of vitamin DThere are strong evidence that vitamin D metabolic enzymes are expressed in virtually all cells in the innate and adaptive arms of the immune system.Regulation of the NF-κB pathway during infectionAlbergamo 2022, [78]To explore the correlation studies between vitamin D deficiency and increased risks of severe COVID-19 disease and, similarly, between vitamin D deficiency and acute respiratory distress syndromeNumerous studies highlight its immunomodulatory and anti-inflammatory properties, and its use was proposed in COVID-19.Decreasing the severe symptoms due to inflammation and oxidative stressGhelani 2021, [79]To consolidate the research surrounding the role of vitamin D in the treatment and prevention of COVID-19.This current study shows evidence wich supports the links between vitamin D and COVID-19 and the benefits of vitamin D supplementation.The toxicity of Vitamin D supplementation is far outweighed by the potential benefits in relation to protection against COVID-19.Biesalski 2020, [80]To establish whether an inadequate vitamin D supply has an influence on the progression and severity of COVID-19 diseaseVarious non-communicable diseases (hypertension, diabetes, CVD, metabolic syndrome), are associated with low vitamin D plasma levels.Vitamin D deficiency increase the risk of severe COVID-19Verdoia M 2021, [81]To determine the potential implications for COVID-19 pandemicVitamin D appears to reduce the acute-phase response associated to a larger pulmonary damage and complications as ARDS or sepsis.Vitamin D modulates the activity of IL-6Weir 2020, [82]To establish if vitamin D supplement would offer a relatively easy option to decrease the impact of the pandemicVitamin D appears to have beneficial effects against COVID-19, it would follow that the severity of the disease should lessen in the Northern hemisphere.Vitamin D, an easy option to decrease
the impact of the pandemic of COVID-19Hribar 2020, [83]To determine the relationship between vitamin D, PD, and COVID-19.Vitamin D may have antiviral properties and play a role in protecting against infections, including respiratory illnesses.2000–5000 IU/day of vitamin D3 in individuals with PD may be beneficial in reducing the risk and severity of COVID-19.