A randomized, placebo-controlled trial on the effects of soy protein containing isoflavones on quality of life in postmenopausal women

OBJECTIVE: Postmenopausal estrogen decline is implicated in several age-related physical and psychological changes in women, including decreases in perceived quality of life (QoL). A number of trials with hormone therapy showed beneficial effects of the intervention on parameters of quality of life. However, because of known or suspected serious side-effects of conventional hormone therapy there is a need for alternatives. DESIGN: We conducted a double-blind randomized placebo-controlled trial with soy protein, containing 52 mg genistein, 41 mg daidzein, and 6 mg glycitein (aglycone weights), or milk protein (placebo) daily for 1 year. For this trial, we recruited 202 postmenopausal women aged 60 to 75 years. RESULTS: At baseline and at final visit, participants filled in the Short Form of 36 questions (SF-36), the Questionnaire on Life Satisfaction Modules (QLS(M)), and the Geriatric Depression Scale (GDS). For the placebo group scores on all dimensions of the SF-36 and the QLS(M) decreased during the intervention year, except for the dimension "role limitations caused by physical problems." The soy group showed increases on two dimensions of the SF-36 ("social functioning" and "role limitations caused by physical problems") and on one dimension of the QLS(M). There were however no statistically significant differences in changes of scores between the two intervention groups. For the GDS similarly, no significant differences were found between the groups. CONCLUSIONS: In conclusion, the findings in this randomized trial do not support the presence of a marked effect of soy protein substitution on quality of life (health status, life satisfaction, and depression) in elderly postmenopausal women.