Asthma is a respiratory disease characterized by inflammation in the airways. The respiratory passages are sensitive and react to certain triggers, causing swelling in the airways. The muscles surrounding the airways contract, or tighten, further narrowing the air passages. In addition, the cells in the airways make more mucus, which clogs the airways. Patients may experience breathlessness, wheezing, coughing and chest tightness. In severe cases, an asthma attack can lead to a loss of consciousness (from a lack of oxygen) and death.

According to the American Academy of Allergy, Asthma and Immunology, about 34.1 million Americans have asthma. The condition affects roughly nine million children under 18. Annually, asthma causes about 217,000 visits to hospital emergency rooms, 500,000 hospitalizations, 12.8 million missed school days, 10.1 million missed work days and more than 3,300 deaths.

Asthma and Vitamin D

Vitamin D is sometimes referred to as the “sunshine” vitamin because sunlight can be converted by our skin into the vitamin. George Macones, M.D., OB/GYN with Washington University in St. Louis, says vitamin D also plays a role in the development of the immune system and healthy lungs. Thus, some researchers believe low levels of the vitamin during pregnancy, when an infant’s lungs are still developing, may increase the risk for asthma in the child. The hypothesis is further supported by studies that show asthma rates in New England (where vitamin D levels are more likely to be inadequate due to low levels of sunlight in the winter) are the highest in the country.

Investigators now want to find out if supplementing a pregnant woman’s diet with high doses of vitamin D may decrease the incidence of asthma in offspring. Macones says the study is enrolling pregnant women with a history of asthma and those for whom the baby’s father has a history of asthma. Half the women will get a high dose of vitamin D (4000 iu of vitamin D3, or colecalciferol) and the standard prenatal vitamin. The other half will take the prenatal vitamin and a placebo.

After the babies are born, the children will have regular follow-ups with a pediatrician to look for signs of asthma in the first few years of life. It will take several years until researchers have enough follow-up data. However, investigators are hopeful the study will determine if supplementation of high doses of vitamin D are safe for mom and baby and reduce the future risk of asthma for the baby.

The study is taking place in St. Louis, Boston and San Diego. For more information, go to http://www.clinicaltrials.gov, then type the trial identification number in the search box: NCT00920621.

For information on the study, go to http://www.clinicaltrials.gov, then type the trial identification number in the search box: NCT00920621.

For general information on asthma:

American Academy of Allergy, Asthma and Immunology, http://www.aaaai.org

Asthma and Allergy Foundation of America, http://www.aafa.org

Centers for Disease Control and Prevention, http://www.cdc.gov/asthma

National Heart, Lung and Blood Institute, http://www.nhlbi.nih.gov