Two conditions associated with ovarian depletion are increased potential for depressive episodes and increased abdominal weight gain. In five different experiments we examined the effect of soy-containing diets or equol injections on depression, serotonin levels, weight gain (BW) and white adipose tissue (WAT) deposition of female Long-Evans rats in various stages of life. Rats were intact, ovariectomized or experienced natural ovarian failure (NOF). While this paper will present each experiment, only experiment 5 is outlined here due to space limitations. From conception the rats were exposed to either a soy-rich (Phyto-600) or low-soy diet (Phyto-low). Animals experienced NOF at approximately 300 days. At 330 days-old animals underwent the Porsolt forced swim test (PFST). One month later (following 1 week of equol injections in Phyto-low fed animals) the animals were again tested in the PFST. Serum was collected before the first PFST and following the second PFST for serotonin and isoflavone analysis. This experiment demonstrated that animals fed a soy-rich diet have decreased BW and WAT compared to a low-soy diet. At the first PFST, the Phyto-low fed NOF females displayed increased immobility and lower serotonin levels compared to the Phyto-600 NOF females indicating the Phyto-low animals were more depressed than the Phyto-600 females. The second PFST demonstrated equol injection significantly increased both time mobile and serum serotonin levels in the Phyto-low fed rats suggesting that equol has antidepressant effects. This experiment demonstrated that isoflavone exposure has antiobesity-like effects. Furthermore, isoflavones (particularly equol) appear to have antidepressant potential in NOF females.



College and Department

Life Sciences; Physiology and Developmental Biology



Date Submitted


Document Type





Rat, isoflavones, behavior, depression, ovarian failure, body weight