Respiratory Health and the “Sunshine” Vitamin
Vitamin D, often dubbed the "sunshine vitamin” is well-known for its role in bone health, but did you know it can also play a role in respiratory health?
Sources of vitamin D
This vitamin is primarily produced through skin exposure to sunlight. Vitamin D is naturally found in certain foods including oily fish (salmon, sardines, herring and mackerel), red meat, liver, egg yolks and fortified foods – such as breakfast cereals.
Once synthesised or ingested, vitamin D undergoes further conversion in the liver and kidneys to become the active form that the body can use for many important functions.
Optimum levels
Most people should be able to make all the vitamin D they need from sunlight. The amount you need depends on many factors such as your age, skin tone and the time of year. Many public health bodies recommend daily vitamin D supplement between October and March.
Vitamin D supplementation is a popular area of research, and it is increasingly clear that a one-size-fits-all approach is not suitable, as a recent study from Trinity College’s School of Medicine outlines.
The study by Brennan et al (2024) sheds a light on the complexities of achieving optimal vitamin D across diverse populations. One key insight is that ambient UVB is a very important predictor of vitamin D status. In short, optimal vitamin D intake very much depends on your individual circumstances.
Links with respiratory health
Vitamin D acts as an immune modulator, this means that it downregulates the production of inflammatory immune markers and upregulates the production of anti-microbial peptides. As such, it is a particularly important vitamin for individuals with chronic respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD) to support the body's ability to fight infections.
The Cystic Fibrosis Foundation states that Vitamin D insufficiency is common among people with cystic fibrosis due to “impaired absorption of fat-soluble vitamins, decreased sunlight exposure, and suboptimal intake of vitamin D-containing foods and/or supplements.”
A systemic review by Raju A. et al (2022) shows that children with vitamin D deficiency are more prone to respiratory infections, and the frequency of vitamin D deficiency increases with age. However, in this study, no conclusive association could be established between vitamin D deficiency and the severity of infections.
Vitamin D improves lung function in asthma
A recent study by Watkins, S. et al (2024) involving asthmatic adults shares the findings of a 12-week double-blind randomised controlled trial, investigating the effect of dietary supplementation of vitamin D.
As part of the study, lung function was measured using the handheld Vitalograph micro™ spirometer. Measurements were taken for forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). The FEV1:FVC ratio is calculated from these measurements and is a commonly used parameter in asthmatics.
Blood samples examined vitamin D metabolism biomarkers (25(OH)D and parathyroid hormone (PTH)) and inflammatory biomarkers including C-reactive protein (CRP) and tumour-necrosis factor alpha (TNF-α).
The test subjects were asked to keep a food diary to capture their dietary intake of vitamin D. They also documented their day-to-day respiratory symptoms using the Asthma Control Test (ACT) questionnaire.
A key finding from the study is that vitamin D supplementation was effective in a “small but statistically significant improvement of the lung function parameter – FEV1: FVC”. The increase in lung function measured by FEV1:FVC ratio was significantly higher in the intervention group compared to the placebo group.
It is encouraging to read how daily dietary supplementation of vitamin D could improve clinical outcomes for asthmatic adults, including lung function and overall vitamin D status.
Check out the paper for more details about this interesting study.
If you have questions about vitamin and mineral intake, check your national public health body or consult with a qualified healthcare professional.
Learn more:
A 12 week double-blind randomised controlled trial investigating the effect of dietary supplementation with 5000 IU/day (125 µg/day) vitamin D in adults with asthma, led to an improvement in the lung function parameter - FEV1:FVC ratio. . Watkins, S., et al (2024). The British journal of nutrition. 1-31. 10.1017/S0007114524000953.
Ambient ultraviolet-B radiation, supplements and other factors interact to impact vitamin D status differently depending on ethnicity: A cross-sectional study. Brennan, Margaret M. et al (2024). Clinical Nutrition, Volume 43, Issue 6, 1308 – 1317
Vitamin D supplementation to prevent acute respiratory infections: a systematic review and meta-analysis of aggregate data from randomised controlled trials. Jolliffe, David A et al (2021). The Lancet Diabetes & Endocrinology, Volume 9, Issue 5, 276 - 292
Health Service Executive of Ireland, Vitamin D, accessed 3 September 2024
Trinity College Dublin. Study challenges one-size-fits-all approach to vitamin D. supplementation guidelines.
A Hospital-Based Study of Vitamin D Levels in Children With Recurrent Respiratory Infections. AP Jaybhaye et al. Cureus, Aug 10;14(8)
Webinar featuring Dermot Ryan, Diagnosing Asthma: Solving the Jigsaw Puzzle
