Soy, isoflavones, and prevalence of allergic rhinitis in Japanese women: The Osaka Maternal and Child Health Study

Background It has been hypothesized that isoflavones reduce the risk of many chronic diseases, but there are no data on the effects of dietary soy and isoflavone consumption on allergic disorders. Objective This cross-sectional study examined the relationship between dietary soy products and isoflavone intake and the prevalence of allergic rhinitis. Methods Study subjects were 1002 Japanese pregnant women. Allergic rhinitis (including cedar pollinosis) was defined as present if subjects had received drug treatment at some point during the previous 12 months. Adjustment was made for age; gestation; parity; cigarette smoking; passive smoking at home and at work; indoor domestic pets; family history of asthma, atopic eczema, and allergic rhinitis; family income; education; mite allergen level in house dust; changes in diet in the previous month; season when data were collected; and body mass index. Results Compared with dietary intake of total soy product, soy protein, daidzein, and genistein in the first quartile, consumption of these substances in the fourth quartile was independently associated with a reduced prevalence of allergic rhinitis, although no significant dose-response relationships were observed. A clear inverse linear trend for miso intake across quartiles was found, whereas the adjusted odds ratio for comparison of the highest with the lowest quartile was not statistically significant. Consumption of tofu, tofu products, fermented soybeans, boiled soybeans, and miso soup was not related to the prevalence of allergic rhinitis. Conclusion A high intake of soy and isoflavones may be associated with a reduced prevalence of allergic rhinitis.