Acute respiratory tract infections (ARTIs), which include upper respiratory tract infections (URTIs), are the most common cause of antibiotic prescription in the UK adult population.
At the same time, the World Health Organization considers that the unprecedented use of antibiotics and subsequent antimicrobial resistance (AMR) is currently one of the largest threats to global health, food security, and human development.
Researchers Dr Emma Derbyshire and Prof Philip Calder have therefore authored a research review to discuss the role of Vitamin D to help prevent RTIs and help reduce AMR.
Given meta-analytical evidence, a growing number of RCTs, and the issue of the global COVID-19 pandemic, they say Vitamin D supplement advice should be updated to include respiratory health benefits and to increase the required dose to 2,000 IU (50 μg) daily.
The current Vitamin D guidelines in the UK have been set at 10 μg daily from October to March (when there is less sunlight) to keep bones, teeth, and muscles healthy.
Dr Derbyshire tells NutraIngredients: “antibiotic resistance is a very ‘real’ reality and not something that we can ignore. Having a lung condition myself I am already aware that I am resistant to two specific types of antibiotic. So we need to pay urgent attention to this problem sooner rather than later and develop novel strategies that could help to take the pressure off current antibiotic usage loads.
"To add to this there have also been additional concerns about high levels of antibiotic usage levels in the fight against COVID-19, which could be further fuelling the threat of antibiotic resistance."
The immune system
The authors explain vitamin D's role in the immune system explaining that vitamin D augments host barrier epithelial integrity by reinforcing intercellular junctions.
It has also been found to trigger antimicrobial peptide production, which exhibits direct pathogen-killing capacity. The vitamin D receptor is expressed on many immune cell types including B-cells, T-cells, and antigen-presenting cells.
Furthermore, some immune cell types, including macrophages and dendritic cells, can synthesize the active form of vitamin D, 1,25-dihydroxyvitamin D3.
As such, vitamin D deficiency has been shown to result in impaired localised innate immunity and a defective antigen-specific cellular immune response, correlated with a higher susceptibility to infections.
Vitamin D metabolites have also been found to influence the expression and secretion of pro-inflammatory chemokines and cytokines, and vitamin D promotes the production of anti-microbial peptides such as cathelicidin.
Derbyshire and Calder note that low levels of 1,25-dihydroxyvitamin D3 have been found to correlate with an increased risk of developing several immune-related disorders including respiratory infection and COVID-19.
Vitamin D has further been found to be involved in pulmonary angiotensin-converting enzyme 2 expression and has the ability to reduce lung surface tension in COVID-19. Other work suggests that vitamin D may induce progesterone-induced blocking factor and exert inhibitory effects on inflammation including the cytokine IL-6, which tend to be elevated in COVID-19.
Respiratory tract infections
The review finds two meta-analyses which focused on observational research. These found inverse relationships between serum 25-hydroxyvitamin D levels and risk and severity of ARTIs and risk of community-acquired pneumonia.
Four meta-analyses focused on RCTs involving findings from vitamin D supplementation programs, meaning they can establish a cause-and-effect relationship. The largest meta-analysis included data from 45 RCTs (n = 73,384 subjects) concluding that daily dosing regimens providing 400–1,000 IU (10–25 μg) of vitamin D were most effective at protecting against ARTIs.
The report concludes: "AMR poses a threat to future global health, and the current COVID-19 pandemic is highly damaging to health, societies, and economies. Urgent responses are needed. Supporting the immune system of the population in advance of exposure to infections (i.e., “immune prehabilitation”) would reduce the number and severity of infections and reduce use of antibiotics. Vitamin D has multiple roles in supporting the immune system."
Vitamin D campaign
The recommendations of the current article are by no means a first. NutraIngredients reported at the end of 2020 that 120 academics and health experts had signed an open letter to the world's governments asking them to increase supplementation guidelines amid this pandemic. The number of signatories is now more than 200.
The letter calls for a recommended vitamin D supplementation of 4,000 IU daily during the pandemic, or at least 2,000 IU.
However, NICE (The National Institute for Health and Care Excellence) still recommends, in general, that people should take 400 IU daily in the winter months and mentions just one benefit, "to maintain bone and muscle health".
Source: Frontiers in Nutrition
Derbyshire. E. J., and Calder. P. C.
"Respiratory Tract Infections and Antibiotic Resistance: A Protective Role for Vitamin D?"