Objective: Dietary soy may improve menopausal symptoms, and subsequently mediate mood. This novel study examines various doses of dietary soy drink on everyday mood stability and variability in postmenopausal women.
Methods: Community-dwelling women (n = 101), within 7 years postmenopause, consumed daily either a low (10 mg, n = 35), medium (35 mg, n = 37), or high (60 mg, n = 29) dose of isoflavones, for 12 weeks. Menopausal symptoms and repeated measures of everyday mood (positive [PA] and negative [NA] affect) (assessed at four time points per day for 4 consecutive days, using The Positive and Negative Affect Schedule) were completed at baseline and follow-up.
Results: The dietary soy intervention had no effect on everyday mood stability (for PA [F{2,70} = 0.95, P = 0.390] and NA [F{2,70} = 0.72, P = 0.489]) or variability (for PA [F{2,70} = 0.21, P = 0.807] and for NA [F{2,70} = 0.15, P = 0.864]), or on menopausal symptoms (for vasomotor [F{2,89} = 2.83, P = 0.064], psychological [F{2,88} = 0.63, P = 0.535], somatic [F{2,89} = 0.32, P = 0.729], and total menopausal symptoms [F{2,86} = 0.79, P = 0.458]). There were between-group differences with the medium dose reporting higher PA (low, mean 24.2, SD 6; and medium, mean 29.7, SD 6) and the low dose reporting higher NA (P = 0. 048) (low, mean 11.6, SD 2; and high, mean 10.6, SD 1) in mood scores. Psychological (baseline M = 18 and follow-up M = 16.5) and vasomotor (baseline M = 4.2 and follow-up M = 3.6) scores declined from baseline to follow-up for the overall sample.
Conclusions: Soy isoflavones had no effect on mood at any of the doses tested. Future research should focus on the menopause transition from peri to postmenopause as there may be a window of vulnerability, with fluctuating hormones and increased symptoms which may affect mood.