1.
Title: Understanding a Low Vitamin D State in the Context of COVID-19.
Walsh, JB, McCartney, DM, Laird, É, McCarroll, K, Byrne, DG, Healy, M, O'Shea, PM, Kenny, RA, Faul, JL
Frontiers in pharmacology. 2022;:835480
Abstract
While a low vitamin D state has been associated with an increased risk of infection by SARS-CoV-2 in addition to an increased severity of COVID-19 disease, a causal role is not yet established. Here, we review the evidence relating to i) vitamin D and its role in SARS-CoV-2 infection and COVID-19 disease ii) the vitamin D status in the Irish adult population iii) the use of supplemental vitamin D to treat a deficient status and iv) the application of the Bradford-Hill causation criteria. We conclude that reverse causality probably makes a minimal contribution to the presence of low vitamin D states in the setting of COVID-19. Applying the Bradford-Hill criteria, however, the collective literature supports a causal association between low vitamin D status, SARS-CoV-2 infection, and severe COVID-19 (respiratory failure, requirement for ventilation and mortality). A biologically plausible rationale exists for these findings, given vitamin D's role in immune regulation. The thresholds which define low, deficient, and replete vitamin D states vary according to the disease studied, underscoring the complexities for determining the goals for supplementation. All are currently unknown in the setting of COVID-19. The design of vitamin D randomised controlled trials is notoriously problematic and these trials commonly fail for a number of behavioural and methodological reasons. In Ireland, as in most other countries, low vitamin D status is common in older adults, adults in institutions, and with obesity, dark skin, low UVB exposure, diabetes and low socio-economic status. Physiological vitamin D levels for optimal immune function are considerably higher than those that can be achieved from food and sunlight exposure alone in Ireland. A window exists in which a significant number of adults could benefit from vitamin D supplementation, not least because of recent data demonstrating an association between vitamin D status and COVID-19. During the COVID pandemic, we believe that supplementation with 20-25ug (800-1000 IU)/day or more may be required for adults with apparently normal immune systems to improve immunity against SARS-CoV-2. We expect that higher monitored doses of 37.5-50 ug (1,500-2,000)/day may be needed for vulnerable groups (e.g., those with obesity, darker skin, diabetes mellitus and older adults). Such doses are within the safe daily intakes cited by international advisory agencies.
2.
Investigating the Relationship between Vitamin D and Persistent Symptoms Following SARS-CoV-2 Infection.
Townsend, L, Dyer, AH, McCluskey, P, O'Brien, K, Dowds, J, Laird, E, Bannan, C, Bourke, NM, Ní Cheallaigh, C, Byrne, DG, et al
Nutrients. 2021;13(7)
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Plain language summary
Persistence of symptoms following COVID-19 infection is known as long COVID and occurs in up to a third of sufferers and can last for as long as 6 months post infection. Tiredness and reduced capacity to exercise are characteristic of long COVID, however why these symptoms persist in a handful of patients is unknown. Vitamin D deficiency is gaining attention for its potential to improve symptoms of tiredness, however there are few studies examining its relationship with long COVID. This observational study of 149 patients who had been diagnosed with COVID-19 aimed to determine the relationship between symptoms of long COVID, inflammation in the body and vitamin D levels. The results showed that fatigue was common, but there was no association between vitamin D levels and fatigue, inflammation, or capacity to exercise. Interestingly women were more likely to experience fatigue in this study. It was concluded that fatigue and reduced exercise capacity are independent of vitamin D in those who have had COVID-19. This study could be used by healthcare professionals to understand symptoms of long COVID, and that vitamin D may not be effective for those symptoms.
Abstract
The emergence of persistent symptoms following SARS-CoV-2 infection, known as long COVID, is providing a new challenge to healthcare systems. The cardinal features are fatigue and reduced exercise tolerance. Vitamin D is known to have pleotropic effects far beyond bone health and is associated with immune modulation and autoimmunity. We hypothesize that vitamin D levels are associated with persistent symptoms following COVID-19. Herein, we investigate the relationship between vitamin D and fatigue and reduced exercise tolerance, assessed by the Chalder Fatigue Score, six-minute walk test and modified Borg scale. Multivariable linear and logistic regression models were used to evaluate the relationships. A total of 149 patients were recruited at a median of 79 days after COVID-19 illness. The median vitamin D level was 62 nmol/L, with n = 36 (24%) having levels 30-49 nmol/L and n = 14 (9%) with levels <30 nmol/L. Fatigue was common, with n = 86 (58%) meeting the case definition. The median Borg score was 3, while the median distance covered for the walk test was 450 m. No relationship between vitamin D and the measures of ongoing ill-health assessed in the study was found following multivariable regression analysis. These results suggest that persistent fatigue and reduced exercise tolerance following COVID-19 are independent of vitamin D.