Lower levels of Vitamin D may worsen asthma and hinder response to steroid treatment.

  Researchers at the National Jewish Health (NJH) in Denver took the vitamin D levels of 54 asthmatics and assessed lung function, airway hyper-responsiveness, which is the prevalence of airway constriction, and response to steroid treatment.

  In those with vitamin levels below 30 nanograms per milliliter (ng/ml), airway hyper-responsiveness almost doubled, compared to those with more D in their blood.

  Low vitamin D levels were also associated with a worse response to steroid therapy and increased production of the pro- inflammatory cytokine, TNF-alpha. This raises the possibility that low vitamin D levels are tied to increased inflammation of the airways, the researchers noted.

  The study was published in the Jan. issue of the American Journal of Respiratory and Critical Care Medicine.

  'Our findings suggest that low vitamin D levels are associated with worse asthma,' said lead researcher Dr. E. Rand Sutherland, from the division of pulmonary and critical care medicine at NJH.

  In addition, vitamin D levels predict how well 'somebody is going to respond to steroidal asthma medications,' he said. 'It may be that vitamin D is acting as a modifier of the immune system or a modifier of steroid response in ways that are relevant to people with asthma.'

  The heaviest participants had the lowest levels of vitamin D, the study noted. Asthma is associated with obesity, and lack of vitamin D may be a factor linking the two conditions, Sutherland said.

  'There is a potential that restoring normal vitamin D levels in people with asthma may help improve their asthma,' Sutherland said.

  But whether vitamin D supplements will help asthmatics isn't known, he added.

  Current recommendations for vitamin D supplements for adults is 400 IU to 600 IU, depending on age, according to the U.S. National Institutes of Health.