In June 2018 researchers from China published the results of their study to assess the association between a regular intake of soy food and depressive symptoms. A total of 3,760 adults (average age 44 years) were involved in the study. Information on dietary intake was collected via a food frequency questionnaire. Symptoms of depression were self-reported by each individual and it was noted that 7% appeared to have an increased level of symptoms. Results showed that when a comparison was made with the lowest intake of soy food (up to once/week), the level of reported depressive symptoms reduced with a soy intake of 1-3 times/week and again for 4-7 times/week, whilst a higher intake appeared to increase the level of symptoms. The researchers concluded by stating that the the results suggested a J-shaped association between frequency of soy food intake and the incidence of depressive symptoms.
Yu B et al. A J-shaped association between soy food intake and depressive symptoms in Chinese adults. Clin Nutr. 2018 Jun;37(3):1013-1018