Lab Study: Problem With Soy Chemical

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Lab Study: Problem With Soy Chemical

Tue May 21, 4:27 AM ET

By PAUL RECER, AP Science Writer

WASHINGTON (AP) - An ingredient in soy-based infant formula tends to weaken

the immune system of laboratory mice, but researchers said they were

uncertain if the chemical would have the same effect in humans.

S. Cooke, a researcher at the University of Illinois, Urbana, said the

chemical, genistein, is found in soy-based baby formula. A study being

released Tuesday says genistein caused the thymus gland in young mice to

shrink and the animals to lose white blood cells.

" What we have done does not prove there is a human problem, " said Cooke,

senior author of the study. " But when you are in a situation where all of

the nutrition comes from something like soy formula, the potential for

something to happen that is deleterious is there. "

The study by Cooke and his colleagues appears Tuesday in the Proceedings of

the National Academy of Sciences (news - web sites).

Soy-based infant formula is used by about 25 percent of the formula-fed

babies in the United States.

Researchers at Illinois fed genistein to young lab mice and found that it

shrank their thymus glands by 50 percent when compared with animals not fed

the chemical.

The test mice also had a dramatic drop in their T-cell count. The T-cell is

a white blood cell that plays a key role in protecting the body from

infection. It is processed in the thymus gland.

Dr. L. Strom of the University of Pennsylvania Center for Clinical

Epidemiology & Biostatistics said the Illinois findings in mice have not

been confirmed in a related study in humans.

Strom was senior author of a study that looked at the health of women, 20 to

34, who had been raised on soy-based formula. He said the study gathered

data on their reproductive health and the frequency of colds and other

infections.

" We did not see any particular problem, " said Strom. " There are no human

data suggesting immune system problems from soy formula. "

Dr. R. Greer, professor of pediatrics at University of Wisconsin and a

member of the nutrition panel of the American Academy of Pediatrics, said

that soy milk has been used commonly since the 1960s for formula-fed babies

who do not thrive on cow's milk formulas.

He said the biggest concern, historically, has been that genistein, an

estrogen-like compound, could have some effect on the female reproductive

system. But studies, including the one by Strom and his colleagues, have

found nothing to raise concern.

" We don't have enough evidence to say that we shouldn't feed soy formula, "

said Greer. When babies do not do well on cow's milk, " you put them on soy

formula and they tend to do better. "

Greer said there are alternative formulas that do not contain soy or cow's

milk " but these are expensive and hard to find. "

" I don't recommend that people stop using soy-based formula, " he said.

Dr. R. , a biochemist at the University of Missouri, said the

science in Cooke's paper " is solid and sound, " but he emphasized that

results are entirely in lab mice.

" Mice certainly aren't humans, " said . " The mouse immune system and

the human immune system differ quite a bit. "

Although said the Cooke study could lead to more research on the

effects of soy milk on babies, " it is unclear that we should be concerned.

" Millions of children, including my own, have used soy formula, " said

.

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On the Net:

Proceedings of the National Academy of Sciences: http://www.pnas.org