Soy isoflavones linked to easier breathing
soy, may suppress the inflammatory process and ease breathing and
explain previous reports linking the isoflavone to reduced asthma
severity, suggests a new pilot study.
The production of inflammatory compounds by white blood cells (eosinophil LTC4) involved in asthma was reduced by 33 per cent, reports the study with 13 asthmatic subjects published in the journal Clinical & Experimental Allergy. The study adds to a small but growing body of data supporting the role of isoflavones in respiratory health. Indeed, epidemiologic studies have linked high dietary genistein consumption with improved airflow in the lungs of asthmatics. "[However,] the molecular mechanisms by which consumption of genistein might attenuate asthma and allergy have not been elucidated," stated lead author Ravi Kalhan from Northwestern University Feinberg School of Medicine in Chicago. According to the European Federation of Allergy and Airway Diseases Patients Association (EFA), over 30m Europeans suffer from asthma, costing Europe €17.7bn every year. The cost due to lost productivity is estimated to be around €9.8bn. The condition is on the rise in the Western world and the most common long-term condition in the UK. The researchers focussed their attentions on the production of the inflammatory leukotriene C4 (LTC4) from white blood cells (eosinophils) among the subjects, assigned to receive a daily soy supplement (100 mg, NovaSoy, ArcherDanielsMidland). The supplement contained 29 mg of genistein, 28 mg of daidzein, and eight mg of glycitein as aglycone. Kalhan and co-workers report that production of eosinophil LTC4 was decreased by 33 per cent, from 3.11 to 2.07 ng/mL at the end of the supplementation period. Moreover, fraction of exhaled nitric oxide (FENO) was also decreased by 17 per cent. FENO reflected the degree of inflammation in the airways. "The reduction in FENO that we report in this study is similar to that seen with the use of moderate-dose inhaled corticosteroids," wrote the researchers. "We therefore think that the 17 per cent reduction in FENO seen in the current study represents a meaningful biological response." Such results are important, said the researchers, since they "further establish that dietary supplementation with these compounds may influence airway inflammation in asthma." "These findings form the rationale for future clinical investigation of dietary supplementation with soy isoflavones, or novel inhibitors of the pathway we have identified, as a strategy to ameliorate asthma and other eosinophil- or leukotriene-mediated diseases," concluded Kalhan. Isoflavones from soy have been shown to provide a number of health benefits, including the promotion of heart health and the maintenance of bone health in post-menopausal women. They have also been studied for their role in cancer prevention and slowing down the ageing process in peri-menopausal women, and have proved to be a popular alternative to HRT for those wishing to control menopause symptoms without resorting to drugs. The study was funded by the National Institutes of Health (NIH), Northwestern University General Clinical Research Center, and The CHEST Foundation-GlaxoSmithKline Clinical Research Trainee Award. Source: Clinical & Experimental Allergy January 2008, Volume 38, Issue 1, Pages 103-112, doi:10.1111/j.1365-2222.2007.02862.x "A mechanism of benefit of soy genistein in asthma: inhibition of eosinophil p38-dependent leukotriene synthesis" Authors: R. Kalhan, L. J. Smith, M. C. Nlend, A. Nair, J. L. Hixon, P. H. S. Sporn
