Nearly 300 million people worldwide have asthma, a chronic inflammatory lung disease that causes wheezing, coughing, chest tightness, and shortness of breath. Asthma is caused by a combination of genetic and environmental factors. Although symptoms can be prevented by avoiding triggers such as allergens and irritants, the prevalence of asthma has increased significantly since the 1970s.
Diet is increasingly recognized as an important risk factor for asthma. Foods that are rich in antioxidants, such as fruits and vegetables might be protective against this disease since decreased consumption of these foods is associated with an increased prevalence of asthma. There is also growing interest in the effects of soyfoods. Their isoflavone content may make them a protective food as well, which could be part of the explanation for the lower rates of asthma in Japan.
Researchers from the Johns Hopkins University School of Medicine compared the isoflavone intake of 300 patients with poorly controlled asthma. They measured isoflavone intake with a questionnaire that assessed intake of soyfoods, which are the only foods that provide relevant amounts of isoflavones. Patients with the lowest isoflavone consumption had worse asthma symptoms. For example, on a test that measured the amount of air that patients could expel from their lungs, those with the lowest isoflavone intake had a reduced capacity that was equivalent to 6 to 7 years of age-related lung function decline. Also, a higher proportion of patients in the low isoflavone group reported an episode of poor asthma control. While more research is needed to confirm the relationship, it’s possible that including soyfoods in your diet could aid in asthma control.
Bime C, Wei CY, Holbrook J, Smith LJ, Wise RA. Association of dietary soy genistein intake with lung function and asthma control: a post-hoc analysis of patients enrolled in a prospective multicentre clinical trial. Primary care respiratory journal : journal of the General Practice Airways Group 2012.