The study of 2,112 adolescents ages 16-19 found that 35% consumed below 200 IU (international units) of vitamin D, the recommended amount for this age group. The researchers found that teens who had a low dietary intake of vitamin D (157 IU or less per day) had significantly lower lung function compared with teens who consumed more, including the recommended amount. There was no difference between girls and boys.
"These are adolescents who should have optimal pulmonary function," said lead researcher Jane Burns, ScD, a research fellow in the Department of Environmental Health at the Harvard University School of Public Health in Boston. "If they're already showing lower pulmonary function associated with lower vitamin D intake at this age, it may have long-term effects on their health."
Vitamin D is found in fortified dairy products, egg yolks, saltwater fish and liver. Some calcium supplements have vitamin D added. Dr. Burns noted that vitamin D is well known as an important nutrient for strong bones because it helps the body absorb calcium. But recent studies have also suggested a role for vitamin D in lung health.
Dr. Burns decided to study teenagers because this age group often has poor eating habits, and so they may be particularly vulnerable to the effects of dietary deficiencies due to their rapid physical growth and development.
"Vitamin D is promoted in terms of bone growth, but we also need to think in terms of vitamin D's other effects on the body," Dr. Burns said. "It may be that we should be promoting dietary vitamin D intake at recommended levels to ensure optimal lung function as well as to form and maintain healthy bones."
While vitamin D's exact role in lung health is not yet known, the nutrient is known to have an effect on the immune system, Dr. Burns said. "We don't know by which mechanism vitamin D affects pulmonary function--it's an area that needs to be explored."