In an article published in the Irish Medical Journal, the research team recommends adults take 20-50 micrograms (μg) of vitamin D per day in order to receive these purported benefits.
“These recommendations are important while we await development of a vaccine and trial evidence of effective drug treatment for Covid-19,” says Dr Declan Byrne, clinical senior lecturer, St James’s Hospital and School of Medicine, Trinity College Dublin.
“Our findings call for the immediate supplementation of all hospital inpatients, nursing home residents and older Irish adults with vitamin D.
“Our findings also suggest that vitamin D supplementation in the broader adult population, and particularly in frontline healthcare workers, may further help to limit infection and flatten the Covid-19 curve,” he adds.
TILDA vitamin D report
The findings also correspond to another recent report that finds the vitamin playing a role in preventing respiratory infections, reducing antibiotic use, and boosting the immune system response to infections.
Here the report, also by Trinity College Dublin highlights the importance of increasing intake especially as one in eight Irish adults under 50 are deficient in Vitamin D.
Further results reveal 47% of all adults over 85 are deficient in winter, while 27% of adults over 70 who are ‘cocooning’ are estimated to be deficient. Lastly, the report finds only 4% of men and 15% of women take a vitamin D supplement.
‘’We have evidence to support a role for vitamin D in the prevention of chest infections, particularly in older adults who have low levels,” says professor Rose Anne Kenny, principal investigator of The Irish Longitudinal Study on Ageing (TILDA).
“Though we do not specifically know the role of vitamin D in COVID infections, given its wider implications for improving immune responses and clear evidence for bone and muscle health, those cocooning and other at-risk cohorts should ensure they have an adequate intake of vitamin D.
“Cocooning is a necessity but will reduce physical activity. Muscle deconditioning occurs rapidly in these circumstances and vitamin D will help to maintain muscle health and strength in the current crisis,” she adds.
Epidemiological studies have shown people with low vitamin D levels have a higher risk of acute respiratory tract infection and community-acquired pneumonia.
While these data do not necessarily infer causality, multiple molecular mechanisms have been identified by which vitamin D deficiency impairs resistance to viral respiratory tract infection.
More studies have indicated vitamin D supplementation may reduce the likelihood of acute respiratory tract infection, and decrease its severity and duration where such infection does occur.
Higher vitamin D3 doses ‘useful’
In another study published this week, a US team 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),” the team adds. “For treatment of people who become infected with COVID-19, higher vitamin D3 doses might be useful.”
They also add that randomised controlled trials and large population studies should be conducted to evaluate these recommendations.
In a response to an article discussing ways to prevent a covid-19 pandemic, Dr Attila Garami, a senior biomarker consultant, highlights that world distribution of COVID-19 fatalities appears to overlap with that of the vitamin D lacking population.
He also mentions that people lacking vitamin D have a weaker innate immune defence against SARS-CoV-2 or the coronavirus.
“Targeting the unbalanced renin-angiotensin system (RAS) with vitamin D supplementation in SARS-CoV-2 infection may be an approach with excellent cost and benefit ratio, to fight the widening of COVID-19,” he comments.
“Clinicians standing in front of SARS-CoV-2 positive patients may easily corroborate the herein assumed correlation between low vitamin D level and worse COVID-19 disease outcome, and so assure us in applying this novel support for COVID-19 patients.”
Inconsistent findings
Despite mounting evidence of vitamin D’s apparent role, the British Nutrition Foundation questions the evidence that vitamin D supplementation reduces the risk of contracting a viral respiratory tract infection (RTI).
Commenting in October last year, Helena Gibson-Moore, a nutrition scientist said that observational studies suggested a link between low vitamin D status and the increased likelihood of developing acute RTIs.
However, systematic reviews of randomised controlled trials (RCTs) with vitamin D supplementation have had mixed results, with some suggesting reduced risk and others showing no effect.
Her comments were supported by a Scientific Advisory Committee on Nutrition review in 2016 that found insufficient evidence to draw firm conclusions and did not support recommending vitamin D supplementation to reduce the risk of RTIs.
The SACN recommended the need for further research particularly large RCTs that look at the effects on participants with low serum concentrations.
“This is to address the concern that many studies to date have investigated mixed groups of participants including those with adequate status,” she said.
“There may be an effect only in those subgroups of the population who are vitamin D deficient. The important point is that more may not necessarily be better – whilst deficiency in vitamin D may have an impact on immunity, once adequate status has been achieved, higher intakes may not be beneficial.”
Source: Irish Medical Journal
Published online ahead of print: Link
“Optimisation of Vitamin D Status for Enhanced Immuno-protection against Covid-19”
Authors: D Mccartney, D Bryne