A recently published study found that adding vitamin D supplements to asthma medication can reduce the severity of symptoms. Researchers noted that an increased risk of asthma attacks is linked to low levels of vitamin D in blood. The study's lead author added that adding a vitamin D supplement to existing asthma treatment reduced the risk of attacks without causing side effects. The team used data from seven medical trials that involved 435 children. Two other studies used by the researchers including 658 adults. However, the supplements did not improve day-to-day lung function.