The effect of Vitamin D status on lung function and airway inflammation in adults in Saudi Arabia and the UK
Vitamin D deficiency is a worldwide health problem and more extensively present in the gulf countries such as Saudi Arabia and in high latitude countries such as the United Kingdom. Many previous cross-sectional studies have investigated the correlation between vitamin D status and lung function, but the effect of vitamin D status on lung function and airway inflammation is still debatable. This project aimed to investigate the effect of vitamin D intervention through pharmacological supplements or dietary intake, on lung function and airway inflammation, among asthmatic adults in Saudi Arabia and in healthy individuals in the United Kingdom. The main findings of the study were; vitamin D deficiency is highly prevalent in asthma participants in Saudi Arabia (86%) and in healthy individuals in the UK (81%). Asthma participants with higher serum vitamin D levels had trend of better lung function (FEV1, P 0.287; FVC, P 0.391), slightly lower fractional exhaled nitric oxide levels (P 0.719) and lower blood inflammatory biomarkers, however, did not reach significant levels. Healthy participants with higher vitamin D levels had also better lung function (FEV1, P 0.104, FVC, P 0.158) but no differences in airway inflammation. Vitamin D intervention through oral supplements or dietary intervention for three weeks, significantly increased serum vitamin D levels (Supplement, P <0.001, dietary, P 0.002) and improved lung function, especially the forced vital capacity (P 0.031), but did not have effects on airway inflammation. Dietary vitamin D intake was lower than the recommendation in both groups. During the study sun-exposure was at the minimal level due to hot weather in Saudi and cold and cloudy weather in the UK. Vitamin D intervention did not affect weight or percentage of body fat. Both chemiluminescence immunoassay and liquid chromatography-tandem mass spectrometry method can be used in measuring serum vitamin D levels but they cannot be used interchangeably due to systematic differences. However, they showed an acceptable agreement levels. Overall, the study found that vitamin D supplement in high dose, low dose or dietary intervention were effective in raising serum vitamin D level and had a trend of positive effect on lung function but not airway inflammation.
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