Preliminary results of a double blind study indicate that adults with asthma who took daily supplements of both vitamins E and C showed improved pulmonary function, compared to when they took a placebo, after being exposed to two common air pollutants, ozone and sulfur dioxide.
Ozone is formed from precursors in automobile exhaust, while sulfur dioxide is emitted from pulp mills, coal burning and other industrial processes.
"Our results show that a combination of antioxidant vitamins can benefit people with asthma who are sensitive to air pollutants," said lead author Dr. Carol Trenga, who conducted the study while completing doctoral research at the University of Washington School of Public Health and Community Medicine. Co-author of the study is Dr. Jane Koenig, an international expert on the respiratory health effects of air pollution.
Trenga presented her preliminary findings on Tuesday, May 20, at the American Lung Association/American Thoracic Society International Conference.
The study monitored pulmonary function in 17 asthmatic volunteers, who took a daily course of vitamins E and C (400 I.U. and 500 mg., respectively) and a daily course of placebo for separate five-week periods.
Near the end of each course, participants received separate, 45-minute exposures to purified air and ozone at the current National Ambient Air Quality Standard (0.12 p.p. million). To measure effects of ozone exposure, volunteers then were exposed to two 10-minute sulfur dioxide challenges.
Test results showed an overall decrease in sensitivity to ozone exposure when volunteers took vitamins as compared to placebo. Improvements in pulmonary function were especially dramatic in a subset of six volunteers. While on vitamin supplementation, this group had a 5 percent increase in peak expiratory flow during the sulfur dioxide challenges after ozone exposure compared to a 13 percent decrease in peak expiratory flow for the same period while on placebo. These volunteers were previously identified as more sensitive to sulfur dioxide.
Trenga explains vitamins E, which is fat soluble, and C, which is water soluble, complement one another, helping increase the potential to reduce oxidative damage in the lungs. When polluted air comes in contact with the lung lining fluid, vitamin C is part of the body's first line of defense, serving to reduce both ozone and free radicals formed by ozone exposure. Vitamin E helps reduce lipid radicals and can be regenerated by vitamin C.
People with asthma may not be the only ones who could benefit from antioxidant vitamin supplements. Increases in daily vitamin intake may also benefit others exposed to chronic oxidative stress--such as smokers or industrial workers, Trenga said.
She adds that future research should focus on linkages between nutritional factors and toxicity and disease. This would include investigating whether regular antioxidant vitamin intake could ultimately reduce the need for medication or frequency of use among people with asthma.