Use of dietary supplements among US adults with asthma

Background: Little is known about dietary supplement use among people with asthma, especially on a national level. We examined the prevalence and type of supplement use and demographic and health-related characteristics of users among US adults with asthma. Methods: Data from the 2005-2006 National Health and Nutrition Examination Survey were analyzed. Asthma was defined by self-report of ever receiving a diagnosis and still having asthma currently. Dietary supplements were collected by direct inspection of products where possible (88% of the time), and were transcribed by trained nutritionists. Multivariate logistic procedure was performed to determine independent associations of supplement use with participant characteristics. Results: The prevalence of using a dietary supplement in the past month was similar between adults with asthma (50.2%, 8.6 million) and those without asthma (54%, 104.3 million). Among asthmatic adults, multivitamins/multiminerals (40.1%) were the most commonly used supplements, followed by vitamin B-12 (23.3%), vitamin C (19.9%), calcium (15.2%), vitamin E (14.7), folic acid (12.7%), vitamin B-6 (11.2%), thiamin (10.8%), niacin (10.8%), B complex vitamins (10.4%), and riboflavin (10.3%). Asthma adults who were supplement users tended to be older (50.2 +/- 19.2 versus 45.2 +/- 18.0 years for supplement users versus nonusers, respectively, P = 0.009), white/Hispanic, women, and had excellent/very good self-reported health. Forty-three percent of supplement users took only one supplement. Middle-aged and older asthma adults were more likely to use multiple supplements concurrently. Conclusion: Use of dietary supplements is popular in US adults with asthma, similar to the general adult population. It is important to take supplement use into account in clinical care for asthma patients and in the design and analysis in epidemiological and intervention studies of nutrition and asthma.