Soy Supplements May Decrease Sexual Drive

ATLANTA--Soy supplements decreased normal sexual behavior by 70 percent in female rats, according to a study lead by Heather B. Patisaul, Ph.D., at Emory University in Atlanta; the study has been submitted for future publication in Hormones and Behavior.

Female rats without ovaries were given either tamoxifen (TAMOX)--a selective estrogen receptor modulator usually prescribed for cancer prevention--by implant or an oral soy isoflavone dietary supplement. The rats were then injected with 10 mcg of estrogen and 48 hours later, injected with 500 mcg of progesterone, thus changing their "normal" hormone levels. Four hours after the injections, the rats were measured for sexual behavior. Proceptive sexual behavior (in the form of hopping and darting) were depressed in both the soy- and TAMOX-treated rats compared to control rats that also received injections; soy supplements decreased proceptive sexual behavior the most compared to the estrogen control group (70 percent) and the TAMOX group (50 percent). Soy supplementation also significantly reduced receptive sexual behavior (pacing and changing posture) in rats compared to that seen in the TAMOX group and the estrogen- and progesterone-treated control rats. Patisaul concluded, "Both soy supplements and tamoxifen act as estrogen antagonists on both proceptive and receptive behavior in female rats."

"We need to look at all aspects of what these compounds are doing," Patisaul told INSIDER, "and our data suggest that decreased sexual performance is an effect that needs to be taken more seriously."