Vitamin D is a steroid hormone and a component of a complex endocrine pathway sometimes called 'vitamin D endocrine system' (Medscape, 2012). The aim of this study was to measure serum vitamin D levels in 500 asthmatic children in Qatar and to compare these to healthy non-asthmatic controls.
How did researchers define vitamin D deficiency?
Subjects with serum containing less than 20 ng/ml vitamin D were deemed deficient.
Asthmatic children had reduced serum vitamin D levels - 68% of all asthmatics were vitamin D deficient. Vitamin D deficiency was the strongest predictor of asthma in this population (OR 4.82).
Why were children deficient in vitamin D?
The majority of asthmatic children had less exposure to sunlight (67%) and less physical activity (71%).
This study revealed that the majority (68%) of asthmatic children had vitamin D deficiency. It remains to be seen if increasing the vitamin D level and correcting the deficiency improves the asthma control. Several studies are currently ongoing that evaluate the effects of vitamin D supplementation in children and adults with asthma. The results are expected in the next 1-2 years.
Vitamin D 1,000 IU/day was inadequate to increase level to more than 30 ng/mL in 50% of asthmatic children after 1 year of supplementation (http://goo.gl/QAWUw).
Severe asthma - differential diagnosis and management (click to enlarge the image). Workup for vitamin D deficiency should probably be included in the evaluation of severe asthma:
Vitamin d deficiency as a strong predictor of asthma in children. Bener A, Ehlayel MS, Tulic MK, Hamid Q. Int Arch Allergy Immunol. 2012;157(2):168-75. Epub 2011 Oct 6.
Image source: Wikipedia, public domain.