A new clinical trial, funded by the National Heart, Lung, and Blood Institute, has found that vitamin D supplements provide no benefit for severe asthma attacks.

Researchers at UPMC Children’s Hospital of Pittsburgh, who published their findings Tuesday in JAMA, found that vitamin D did not prevent severe asthma attacks in at-risk children.

Lead author Dr. Jaun Celedón said, “The reason that’s important is there are colleagues around this country and worldwide who are testing vitamin D levels for kids with asthma and giving them vitamin D.”

“As a system, it costs a lot of money to run all these tests and give the supplements,” he added. “We’ve shown no benefit for children with moderately low vitamin D levels.”

The Vitamin-D-Kids Asthma (VDKA) Study examined nearly 200 children between the ages of 6 and 16 across seven different hospital systems in the United States. All the participants had at least one asthma attack before the study began. The researchers followed up with the participants for three years.

In the trial, half of the participants received 4,000 IU of vitamin D per day, while the other half were given a placebo. All of the participants had vitamin D levels low enough that supplements can have an effect.

The study, however, did not involve children who had severe vitamin D deficiency.

When compared with the placebo group, vitamin D supplements failed to prevent or reduce the number of asthma attacks in at-risk children, contradicting previous observational studies, which have found that children with vitamin D deficiency seemed to have worse asthma.

Dr. Celedón said, “With observational studies, you never know — is vitamin D causing asthma to be worse or do kids with worse asthma end up having lower vitamin D?” Considering the findings of the current study, Dr. Celedón acknowledged that he cannot conclude whether very low vitamin D levels actually contribute to asthma attacks. However, he argued that those at-risk children would anyway be supplemented with vitamin D because of its effects on bone health.