by Kurt Pfitzer
-conscious Americans have long accepted the benefits of tofu, infant formula and other food products made from soybeans and soy extract.
But their assumption is now being called into question by Jill Schneider, associate professor of biological sciences at Lehigh University in Bethlehem, Pennsylvania.
In a study of hamsters completed under Schneider's direction, Jamie Swanson, a biological sciences major, recently found that a component of soy beans -- isoflavones -- significantly accelerated the onset of puberty in the rodents.
These findings, which are similar to the results reported by labs that have experimented with rats, might be relevant to humans, Schneider says. She points out that many babies who are allergic to cow's milk are fed soy-based formulas that contain isoflavones. Isoflavones, she says, can act like estrogen, a natural hormone important in the development of both male and female humans.
Besides triggering early puberty in hamsters, Schneider and Swanson found that early exposure to soy isoflavones also influenced the sexual behavior of the rodents, long after they had stopped eating the isoflavones.
"The sexual behavior of the soy isoflavone-treated animals was much more pronounced," Schneider says. "They showed much more sexual receptivity and more interest in mating.
"Like estrogens, these isoflavones can work early in development and change how an animal acts later."
The experiments conducted by Swanson, says Schneider, "provide evidence that isoflavones might have far-reaching effects on behavior. People should be concerned about giving these formulas with isoflavones to infants. They should not necessarily jump on the bandwagon to consume these products."
Scientists do not yet know whether there is a safe dose of isoflavones for infants, Schneider says. But infants who are fed soy formula containing isoflavones should be monitored later in their lives to see if they experience accelerated onset of puberty.
Schneider also advocates examining sex differences in response to isoflavones, to see if they affect baby boys differently from baby girls. And she believes it would be prudent to try to measure the possible long-term benefits of soy formulas, such as lowering the incidence of obesity and diabetes.
Schneider's concern about the effects of soy products goes further. While some people believe soy products protect women against heart disease and other ailments, she says, the products might be linked to a number of health risks including breast cancer and accelerated aging in the brain. Estrogen stimulates cell division and growth in some types of breast cancers. Isoflavones, which bind to estrogen receptors, can mimic estrogen in some cases, Schneider says.
Naturally occurring soy products like soy beans or tofu, Schneider says, do not concern her as much as the isoflavone pills or concentrated soy powders, which contain larger quantities of isoflavone than those contained in the the beans or curd.
Schneider, who presented her findings in a paper before the Society for Neuroscience in November, says investigators have asked the FDA not to allow soy manufacturers to claim their products are good for health.
"I would not feed infants soy products. I would breast-feed. If for some reason a woman can't breast-feed, I would not recommend feeding infants foods that are high in isoflavones."
November 26, 2001 (http://www.monitor.net/monitor) All Rights Reserved. Contact firstname.lastname@example.org for permission to use in any format.
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