Thursday, June 08, 2006

Tide Is Turning on Soy

Long touted as a miracle food, the tide is turning on soy:

Perhaps no food could withstand the hype heaped on soy. But with more rigorous examination, the bean's starry promise seems to be crumbling.

In January, the American Heart Association published an advisory pulling back on its 2000 stance on soy, which had recommended "including soy protein foods in a diet low in saturated fat and cholesterol."

January's statement said that a review of 22 studies showed that soy protein with isoflavones did not, after all, seem to improve cholesterol.

This April, there was more bad news. Many women consume soy or soy supplements in the hope of preventing breast cancer, but a study in the Journal of the National Cancer Institute concluded that though soy may very slightly reduce the risk of breast cancer, it's not enough to recommend it.

For breast-cancer survivors, taking soy supplements (as opposed to soy-based food) could actually be ill-advised, says study co-author Robert Clarke, a professor at Georgetown University's Lombardi Comprehensive Cancer Center.

Unlike soy foods, supplements contain high levels of estrogen-like isoflavones, such as one called genistein. And estrogens coax breast-tumor cells to divide, says co-author Leena Hilakivi-Clarke, a professor of oncology at Georgetown.

The hot-flash connection also has begun to erode. In early trials, soy isoflavones reduced hot flashes by 9 to 40 percent in menopausal women, but most of the 25 or so trials done later showed no difference from placebos.

A few scientists are actually voicing fears about soy's safety.

Some are worried about reproductive problems. Last year, researchers at the National Institute of Environmental Health Sciences (NIEHS) found that mice given genistein right after birth developed irregular reproductive cycles and problems with ovulation and fertility. This year, they reported that genistein disrupted the development of ovaries.

"Whether these things cause problems in humans, we just don't know," says Wendy Jefferson, an NIEHS scientist and the paper's lead researcher. "But so many babies are on soy formulas. If these things are going to be a problem it is a problem that would only manifest later, when a woman was trying to get pregnant, or having reproductive-cycle problems."

The research led an independent panel of 14 scientists to meet in March and decide whether soy formula is hazardous to human development or reproduction.

The panel concluded that soy formula was safe but one pediatrician on the panel expressed concerns, saying exposure to soy formula occurs during a critical time in infancy and might possibly affect development of the brain and reproductive system.

But the news isn't all bad:

Even as some soy fears grow and much of its promise is being shot down, new possibilities are popping up.

A recent study suggested that if women consume soy during the third trimester of pregnancy, it could help program fetuses with a craving for healthful foods and a good metabolism.

Others suggest that when women eat soy could be key. Research by Anna Wu, professor of preventive medicine at the University of Southern California, suggests that girls who eat a lot of soy during adolescence may be less likely to get breast cancer later.

And bone strength may be one place where soy really delivers. A three-year, $3.4 million study funded by the National Institutes of Health is testing whether soy isoflavone supplements can help preserve bone in the lower part of the lumbar spines in post-menopausal women.
. . . .
Nutritionists watch the very public taking down of soy with bemusement — and slight exasperation. Many point out that meta-analyses (which pool results of different studies) are not the best way to judge a food or medicine.

But they also see the fall of soy as part of the cycle of pop culture, be it celebrity or bean: Hoist it up to impossible heights, then drag it down and bash it. The truth, they say, is somewhere in the middle.


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