People with asthma who have low levels of vitamin D fare worse than those with high levels of the "sunshine" vitamin, a new study finds.

Researchers found that asthmatics with high vitamin D levels have better lung function and respond better to treatment than asthmatics with low vitamin D levels do.

"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 National Jewish Health in Denver.

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."

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