A study published in the medical journal *Allergy, Asthma & Immunology Research* in September 2013 shows that low blood levels of vitamin D are associated with worsened asthma symptoms. The researchers analysed 25-hydroxyvitamin D levels in the blood of 121 adult asthma patients. Those with the lowest 25-hydroxyvitamin D levels had more severe asthma than those with higher levels of 25-hydroxyvitamin D.
