Negative soy effects

[Guest guest]

I've seen some recent discussions here on soy. I came across this article

recently. This is the first such study I've seen on these sort of behavior

problems associated with soy consumption.

In male monkeys, too much soy has adverse effects

April 30, 2004

Wake Forest University School of Medicine

While soy may be beneficial to women in a variety of ways, research in monkeys

suggests that it could have an adverse effect on the behavior of men.

While soy may be beneficial to women in a variety of ways, research in monkeys

suggests that it could have an adverse effect on the behavior of men, according

to researchers from Wake Forest University Baptist Medical Center.

Reporting in the current issue of the scientific journal Hormones and Behavior,

the researchers found that in male monkeys, " long-term consumption of a diet

rich in soy isoflavones can have marked influences on patterns of aggression and

social behavior. " Isoflavones are a naturally occurring plant estrogen in soy

protein.

" Although considerable attention has been directed at the potentially beneficial

effects of isoflavones in reducing the risk of various cancers, osteoporosis,

cardiovascular disease and postmenopausal symptoms, less effort has been

invested in characterizing neurobehavioral effects, " according to the study.

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 FDA approved a statement in 1999 that said, " 25 grams of soy protein a day,

as part of a diet low in saturated fat and cholesterol, may reduce the risk of

heart disease. " Soy sales have grown from $940 million in 1990 to a projected $4

billion this year. Kaplan said that soy is the most widely used botanical by

pre- and postmenopausal women.

" To the best of our knowledge, the present study may be the first to demonstrate

that long-term consumption of isoflavones can alter patterns of agonistic and

social behavior in primates, " the researchers reported. " The present findings

suggest that careful attention will be required to balance beneficial and

potentially adverse effects. "

Other researchers in the study included R. , D.V.M., professor of

pathology, and C. Register, associate professor of pathology, at Wake

Forest Baptist, as well as two researchers from Lehigh University's Department

of Biological Sciences.

The research was funded by NIH grants and a grant from the HF Guggenheim

Foundation.