A study on mice says

Jan 11, 2006 10:49 GMT  ·  By

A new study comes to back the theory which says that soy-based products are not as healthy as vegetarians all over the world claim.

Researchers at the National Institute of Environmental Health Sciences (NIEHS) found that genistein, a major component of soy, disrupts the development of the ovaries in newborn female mice that were given the product. It's difficult to tell if the effects on mice will translate to the human population in the exact same way, still, Dr. David A. Schwartz, Director of the Institute warns that this discovery should be taken into consideration.

"Although we are not entirely certain about how these animal studies on genistein translate to the human population, there is some reason to be cautious. More clinical studies are needed to determine how exposure during critical windows of development can impact human health," he said. Genistein can be found in foods containing soy such as soy-based infant formulas as well as over-the-counter dietary supplements.

"We knew genistein was linked to reproductive problems later in life, but we wanted to find out when the damage occurs. The study showed that genistein caused alterations to the ovaries during early development, which is partly responsible for the reproductive problems found in adult mice," said Retha R. Newbold, endocrinologist at NIEHS and an author of the study.

Female mice were injected with three different doses of genistein during their first five days of life. The genistein given to the mice was comparable to what human infants might receive in a soy-based formula, which is approximately 6-9 mg/kg per day. The researchers examined the effects on days 2 through 6.

The researchers found effects at all levels. Mice treated with the high dose (Gen 50 mg/kg) were infertile and mice treated with lower doses were subfertile, meaning they had fewer pups in each litter, and fewer pregnancies "I don't think we can dismiss the possibility that these phytoestrogens are having an effect on the human population. They may not show their effects or be detected until later in life, but chances are they are having an effect," another researcher said.

A previous study carried out by the University of Colorado showed that the health of mice carrying a genetic mutation for a disease that is the leading cause of sudden cardiac death in people under 30 worsened considerably when the animals were fed a soy-based diet.

According to the author, male mice carrying the mutation for hypertrophic cardiomyopathy, or HCM, were severely affected by the soy diet, exhibiting progressively enlarged heart muscles and eventual heart failure. When the mice in the study were switched to a diet of the milk protein, casein, the condition of the males improved significantly.

In light of the new discoveries, the researchers recommend more attention be paid when establishing soy-based diets, especially for newborns.