Dr Stephanie Watkins

Vitamin D deficiency has previously been linked to higher rates of exacerbation and reduced lung function in asthmatics. Previous randomised controlled trials (RCT) investigating the effect of vitamin D supplementation have mainly focussed on children with asthma. Trials involving adults have typically used bolus dosing regimes and the main outcomes have been patient focussed without investigating underlying inflammation. The present study aimed to conduct a 12-week placebo-controlled RCT administering a daily 5000 IU (125 µg) vitamin D3 supplement to adults with mild to moderate asthma. A total of 32 participants were randomised to receive either the 5000 IU vitamin D3 supplement or an identical matching placebo. The primary outcome of the study was lung function measured by ratio of FEV1:FVC (effect size 2.5) with secondary outcomes including asthma symptoms and inflammatory biomarkers. There was a small but statistically significant higher increase in the mean (± SD) ratio of FEV1: FVC from baseline to post-intervention in the vitamin D group (+ 0.05 ± 0.06) compared to the placebo group (+ 0.006 ± 0.04, p = 0.04). There was no effect of the intervention on asthma control test scores, or the inflammatory biomarkers measured. There was a moderate, significant association between baseline plasma 25(OH)D concentration and baseline plasma IL-10 (r = 0.527, p = 0.005) and TNF-α (r = -0.498. p = 0.008) concentrations. A daily vitamin D3 supplement led to slightly improved lung function in adult asthmatics and may be a useful adjunct to existing asthma control strategies, particularly for individuals with suboptimal vitamin D status.

Objective:

The aim of the present study was to develop and validate a vitamin D FFQ for assessment of dietary vitamin D intake in healthy adults in England, UK.

Design:

The current study assessed the agreement between a four-day food diary (4 d-FD) and a new vitamin D FFQ to measure dietary intake of vitamin D. Dietary intake was estimated using Nutritics dietary analysis software, and Spearman’s and Bland–Altman tests were utilised to assess correlation and agreement, respectively. Participants also provided a blood sample for plasma analysis of vitamin D concentrations.

Setting:

Home setting.

Participants:

Fifty participants were recruited to the study from the University of Chester and vicinity.

Results:

Results showed a strong correlation between vitamin D intake recorded by the FFQ and the 4 d-FD (r = 0·609; P < 0·0001) within 95 % limits of agreement. Furthermore, a significant correlation between plasma 25(OH)D concentrations and vitamin D intake measured by the FFQ (r = 0·290, P = 0·041) and the 4 d-FD (r = 0·360, P = 0·01) was observed.

Conclusion:

Our analysis suggests this FFQ is a useful and rapid tool for researchers and health professionals to assess vitamin D dietary intakes in healthy adults in the UK.

Vitamin D deficiency has been linked to asthma in adults and is thought to be associated with reduced lung function(Reference Han, Forno and Celedón1). Previous observational studies found an association between low serum or plasma vitamin D (25(OH)D) concentrations and reduced lung function in asthmatics(Reference Black and Scragg2). Clinical trials investigating the effect of vitamin D supplementation in people with asthma have mainly focussed on children(Reference Checkley, Robinson and Baumann3), with varied results in adults(Reference Shabana, Esawy and Ismail4, Reference Sluyter, Camargo and Waayer5, Reference Sharma, Kumar and Dhasmana6). Many clinical trials have investigated the effect of bolus dosing and have focussed on patient outcomes without accounting for levels of underlying inflammation. The aim of the present research was to conduct a 12-week randomised controlled trial investigating the effect of a daily 5000 international unit (IU, 125μg) vitamin D3 supplement on lung function and inflammatory markers in adults with mild to moderate asthma.

This study was approved by the Faculty Research Ethics Committee and registered with clinicaltrials.gov (NCT04117581). A total of 32 participants were recruited and randomised to receive either a daily 5000 IU vitamin D3 supplement or identical placebo for 12 weeks. A total of 27 participants completed the trial. The primary outcome was lung function measured by ratio of forced expiratory volume in one second (FEV1) to forced vital capacity (FVC). Secondary outcomes included asthma control test score and measurement of inflammatory biomarkers (CRP, IFN-γ, TNF-α, IgE, IL-10, IL-13 and IL-4).

Insufficient (< 50 nmol/L) and deficient (< 25nmol/L) vitamin D status was common in participants at baseline: 59% and 22% respectively. The intervention resulted in a significantly higher increase in the mean (± SD) ratio of FEV1: FVC from baseline (week 0) to post-intervention (week 12) in the vitamin D group (+ 0.05 ± 0.06) compared to the placebo group (+ 0.006 ± 0.04, p = 0.04). There was no effect of the intervention on asthma control test scores or the inflammatory biomarkers measured. However, there was a strong, significant positive association between mean change in plasma 25(OH)D concentration and mean change in plasma IL- 10 concentration (r = 0.622, p = 0.023). This suggests the improvement in participants’ vitamin D status in the vitamin D group led to increased levels of this anti-inflammatory biomarker, which may contribute to reducing levels of inflammation in asthmatics.

A daily vitamin D3 supplement, at a dose above current UK recommendations, led to increased lung function in adult asthmatics and may be a useful adjunct to existing asthma control strategies.