Child asthma rates have been rising in many parts of the world for many years, disrupting lives and driving up healthcare costs, but there may be new reason for hope to begin reversing the trend.

A new Harvard Kennedy School Faculty Research Working Paper study co-authored by Professor Richard Zeckhauser finds data-driven support for the hypothesis that vitamin D gained through exposure to sunshine during the middle of one’s pregnancy significantly reduces subsequent asthma incidence in the child. Zeckhauser developed the study along with co-authors Nils Wernerfelt of MIT and David Slusky of Princeton University.

“We find highly significant evidence that an increase in sunlight in an individual’s location during the second trimester in utero reduces his/her probability of becoming asthmatic,” the authors write. “This result is consistent with pre-existing research from the fetal development literature which has found substantial evidence suggesting vitamin D is particularly important during this period for asthma pathogenesis.”

One in 12 Americans suffers from asthma, costing them more than 50 billion dollars a year in treatment and lost productivity. Zeckhauser and his co-authors argue that public policies designed to augment vitamin D levels in pregnant women – a large majority of whom are vitamin D insufficient – could greatly reduce those costs while enhancing children’s health.

“Our results suggest that if we could raise vitamin D levels in these women [during the second trimester], the savings in terms of both future quality of life and healthcare costs could be substantial,” they write.