Low vitamin D levels shown to raise risk of hospitalization with potentially fatal respiratory tract infections by 33%

Severe vitamin D deficiency is associated with a higher rate of hospitalisation for respiratory tract infections such as bronchitis and pneumonia, according to a new study led by the University of Surrey. Scientists found that those with a severe deficiency (below 15 nnmol/L) were 33 per cent more likely to be admitted to hospital for treatment than those with sufficient levels of vitamin D (at least 75 nmol/L). 

In the largest study of its kind, analysing NHS data from the UK Biobank, researchers from Surrey, in collaboration with the University of Reading and University of Oxford, investigated the association between vitamin D status and the rate of hospitalisation due to respiratory tract infections. Middle and older-aged adults are at a high risk of developing respiratory tract infections, with lower respiratory tract infections (pneumonia and bronchitis) ranking amongst the top 20 leading causes of mortality globally for individuals aged 50-74 years and in the top 10 for those aged 75 years and older. 

Abi Bournot, BBSRC Food Biosystems PhD Research Fellow and Lead Author at the University of Surrey, said:

“Vitamin D is vital to our physical wellbeing. Not only does it keep our bones and muscles healthy, its antibacterial and antiviral properties are also thought to help reduce the risk of respiratory tract infections that can lead to hospitalisation. This research attaches hard data to support the theory. Despite its importance to our overall health, many people are deficient and do not meet the government’s recommended intake of 10 micrograms of vitamin D per day.

“Supplementation of the vitamin, especially in the winter months when our exposure to sunlight is limited, is an effective way of increasing vitamin D and reducing the risk of serious respiratory tract infections. This is particularly important for older people who are at higher risk of death from such infections, and ethnic minority communities in the UK, who are at a higher risk of vitamin D deficiency.”

Examining data from 36,258 participants from the UK Biobank, researchers found that those with severe vitamin D deficiency (below 15 nmol/L) had a 33 per cent higher rate of hospitalisation for a respiratory tract infection, compared to those who had vitamin D levels of 75 nmol/L or greater. Scientists also found that for each 10 nmol/L increase in vitamin D, the hospitalisation rate for respiratory tract infections decreased by four per cent.  

Dr Andrea Darling, BBSRC-funded Postdoctoral Researcher at the University of Surrey and Senior Author of the study, said:

“Respiratory tract infections are a major threat to public health globally. Not only can they make an individual feel very unwell in many cases, they can also lead to hospitalisation which puts strain on an already stretched health service.

 “Our findings of a significant association between increased vitamin D levels in our bodies and reduced hospital admission rates warrants further study, and points to the potential for vitamin D supplementation and consumption of vitamin D fortified foods to reduce the risk of hospitalisation with respiratory infections in the future, and therefore mitigate pressures on the NHS.”

This study was published in The American Journal of Clinical Nutrition

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Notes to editors:

• Abi Bournot and Prof Susan Lanham-New are available for interview on request.
•  For more information, please email mediarelations@surrey.ac.uk

Paper title: ‘Association between serum 25-hydroxyvitamin D status and respiratory tract infections requiring hospital admission: unmatched case-control analysis of ethnic groups from the UK Biobank cohort’

Authors: Abigail R. Bournot (University of Surrey), Kathryn H. Hart (University of Surrey), S. Johnsen (University of Surrey), D.Ian Givens (University of Reading), Julie A. Lovegrove (University of Reading), José M. Ordóñez-Mena (Nuffield Department of Primary Care Health Sciences,) Simon de Lusignan (Nuffield Department of Primary Care Health Sciences), David B. Bartlett (University of Surrey), Susan A. Lanham-New (University of Surrey) and Andrea L. Darling (University of Surrey)

 DOI: 10.1016/j.ajcnut.2025.101179