People have the concept that soy is only beneficial, said Jay R. Kaplan, Ph.D., professor of comparative medicine and anthropology, one of the investigators. "There is the thought that what is good for some is good for all and more is better."
But this research points out that not only does the dose make a difference, but so does the sex of the consumer, Kaplan said, adding that the study is consistent with emerging literature showing that soy can have a negative impact on the behavior of male rodents. Previous studies have shown no difference in aggression in females given large doses of soy, Kaplan said.
The study was done over 15 months with adult male monkeys who were divided into three groups and fed different amounts and types of protein. One group had about 125 mg of isoflavones a day. The second group had half that amount, and the third group's protein came from milk and animal sources.
"In the monkeys fed the higher amounts of isoflavones, frequencies of intense aggressive and submissive behavior were elevated," according to the study. "In addition, the proportion of time spent by these monkeys in physical contact with other monkeys was reduced by 68 percent, time spent in proximity to other monkeys was reduced 50 percent and time spent alone was increased 30 percent."
Isoflavone levels of 125 mg per day are higher than amounts consumed by many Asians, who typically eat more soy than other populations. But, the isoflavone levels are comparable to levels found in many dietary supplements sold in the United States.
The fact that it increases both aggressive and submissive behavior is curious. Did it increase aggression in some monkeys and submission in others? Or was it a function of circumstance with the same monkeys showing more of each behavior?
Steroid use by athletes causes violent outbursts popularly known as "roid rage". Does the combination of soy and steroids act synergistically to produce even more violent behavior?
Will gang members or other deviants start using isoflavones in order to make themselves more aggressive?
|Share |||Randall Parker, 2004 May 04 10:38 AM Brain Violence|