Soy isoflavone intake is not associated with the development of cedar pollinosis in adults.

Although soy isoflavone has been suggested to have both immune-enhancing and immune-suppressive effects, the effects of soy isoflavone intake on allergic disorders are unclear. A cross-sectional study indicated that a high intake of soy isoflavone is associated with a decreased risk of allergic rhinitis. We aimed to prospectively examine the relationship between soy isoflavone intake and risk of cedar pollinosis, the most common seasonal allergic rhinitis in Japan. The study was conducted in a population-based cohort of Japanese men and women. Each subject's usual diet, including soy isoflavone intake, was determined with the use of a validated FFQ in 1992. In 2002, a total of 11,229 persons who were 35-69 y old and had no history of cancer or allergic diseases at the baseline responded to a follow-up questionnaire asking about 4 symptoms related to cedar pollinosis. Cox hazard regression model was used to determine the association between soy isoflavone intake and the risk of cedar pollinosis. During the 10-y follow-up, 931 of these subjects reported that they had cedar pollinosis. There was no significant association between soy isoflavone intake and risk of cedar pollinosis in men and women after controlling for covariates. For the highest compared with the lowest quartile of soy isoflavone intake, hazard ratios were 1.07 (95% CI: 0.81-1.42) in men and 0.89 (95% CI: 0.68-1.15) in women. These data did not support an association between soy isoflavone intake and risk of cedar pollinosis.