In March 2018 researchers from Japan published the results of their study to assess the association between the intake of soy products and isoflavones and the incidence of depressive symptoms during pregnancy. A total of 1745 pregnant women were included in the study. Information on dietary intake during the preceding month was collected via a self-administered diet history questionnaire. Depressive symptoms were assessed and defined by a score of 16 or over. Results showed that a higher intake of total soy products, tofu, tofu products, fermented soybeans, boiled soybeans, miso soup, and isoflavones was independently related to a reduced incidence of depressive symptoms during pregnancy. A further analysis revealed a significant dose-response association between miso intake and depressive symptoms, in that the higher the intake the lower the incidence of depression. However, no association between the intake of soya milk and depressive symptoms during pregnancy was observed.
Miyake Y et al. Soy isoflavone intake and prevalence of depressive symptoms during pregnancy in Japan: baseline data from the Kyushu Okinawa Maternal and Child Health Study. Eur J Nutr. 2018 Mar;57(2):441-450.