According to a new study from a University of Kansas economist and colleagues, the most efficient way of reducing the chances of children developing asthma might be as simple as ensuring their mom gets enough vitamin D during her pregnancy’s second trimester.
The most cost-effective and practical way for anyone to get vitamin D is to spend as little as 10 minutes a day in the sun, said David Slusky, assistant professor of economics at Kansas. The Centers of Disease Control and Prevention estimates that 1 out of 12 Americans is asthmatic.
“Our health system spends billions and billions treating asthma, and there’s lots and lots of opportunity costs,” said Slusky in a press release. “Pain and suffering, loss of productivity and premature death — asthma has all of those.”
Slusky was aware of a recent hypothesis in the medical field suggested by Scott Weiss and Augusto Litonjua, physicians at the Brigham and Women’s Hospital in Boston and professors at Harvard Medical School. The pair hypothesized that the levels of vitamin D in the second trimester of a woman’s pregnancy influenced the likelihood of the baby to develop asthma later in life.
Slusky and his colleagues, Nils Wernerfelt from the Massachusetts Institute of Technology (MIT) and Richard Zeckhauser from Harvard’s Kennedy School, decided to test the hypothesis by using easily available tools, such as surveys and health data, which are generally used for their economics studies.
“This is the golden age in the way that data about hospital discharges, insurance claims, birth certificates and death certificates are more and more available and more and more set up for researchers,” Slusky said. “And that allows economists to get really large sample sizes with not a lot of cost.”
First, the economists used data from hospital discharges in two different states and from a national survey to look at where and when asthma patients had been born. Then the team searched for sunlight measurements in these patients’ birth locations when their mothers would have been going through their second trimester of pregnancy.
The study found that a pregnant woman’s increased sunlight exposure, and thus vitamin D levels, did indeed appear to lower a child’s probability of developing asthma. The team took relative differences into account due to concerns about profound geographic disparities in individuals’ backgrounds.
“We’re not looking at sunny places versus non-sunny places,” Slusky said. “We looked at the relative differences of the level of sunlight at a particular place at a particular time of year.”
For instance, people who were born in Georgia in the month of July, 1978, received a significantly different sun exposure in utero than their fellow Georgians in 1979. “If that place is relatively more sunny during the second trimester, we found relatively lower rates of asthma,” Slusky said.
“Calibrating this into the proper policy recommendation is something I’ll leave to others, but I think that’s where this research is going,” Slusky said. “Clearly if I’m going to the beach or going to spend all day outside, I need to put on sunscreen. But spending 10 minutes outside without it may not be such a bad idea.”
According to the team, a minimum of 10 minutes in the sun daily is all that’s needed to get more vitamin D during pregnancy and lower the chances of a child developing asthma. Many in the medical community agree that most of us would benefit from a daily dose of the sunshine vitamin, as well.
“Skin cancer is a very serious disease, and I don’t want to minimize it, but at some point that extra minute you spend inside is costing you more vitamin D than it’s helping you not get skin cancer,” Slusky said. If a person is unable to be in the sun for the free supply of vitamin D, dietary supplements are always available – most prenatal vitamins include it.
Officials in Australia are becoming more aware of vitamin D deficiencies, and they are urging schools to relax rules regarding children wearing hats in the country’s winter months of June and July, according to the study.