To determine if micronutrient intake is associated with asthma severity, we administered the Block food frequency questionnaire to participants in a randomized clinical trial of the safety of influenza vaccine for asthmatics. The nutrition substudy included 1033 participants, aged 12-75. Intake of antioxidant vitamins, soy isoflavones, total fruits and vegetables, fats, and fiber was compared with asthma severity at baseline [forced expiratory volume in 1 second (FEV1), peak expiratory flow rate (PEF), asthma symptoms] and the rate of asthma exacerbations during the 2 weeks following influenza vaccination. The only nutrient that had a consistent association with asthma severity was genistein, a soy isoflavone. None of the nutrients evaluated were related to asthma exacerbation rate when adjusted for known confounders. The FEV1 in genistein consumers of at least 250 μg/1000 Kcal/day was 82.1% predicted, 79.9% predicted for those who consumed between 1 and 249 μg/1000 kcal, and 76.2% predicted in genistein nonconsumers (p=0.006); the PEF was 82.7% predicted, 80.8% predicted, and 78.3% predicted, respectively (p=0.009). There were no differences in the Asthma Symptom Utility Index (ASUI). We could not account for these results based on differences in demographics, body mass index, or consumption of other nutrients. Thus, increasing consumption of genistein is associated with better lung function in patients with asthma. Further studies are needed to determine whether dietary supplementation with genistein can reduce asthma severity.
Bibliographical noteFunding Information:
The authors thank Linda Van Horn, Ph.D. for assistance with the food frequency questionnaire. The study was supported by grants from the American Lung Associations of Alabama, Central Florida, Colorado, Delaware, Eastern Missouri, Finger Lakes (New York), Georgia, Gulfcoast Florida, Hudson Valley (New York), Illinois, Indiana, Louisiana, Maine, Metropolitan Chicago, Michigan, Mid-Ohio, Minnesota, Nassau-Suffolk (New York), New Hampshire, New York City, North Carolina, Northeast Florida, Ohio, Oklahoma, Pennsylvania, South Florida, Southeast Florida, Texas, Vermont, Western Missouri, Wisconsin, Greater Norfolk County (Massachusetts), Hawaii, Middlesex County (Massachusetts), New York State, Northern Rockies, Queens (New York), Western Massachusetts, and Virginia; Baylor College of Medicine; The Thalheim Family; Duke University; the Ernest N. Morial Asthma, Allergy, and Respiratory Disease Center; the Merck Foundation; and Glaxo SmithKline.
- Soy isoflavones