To the disappointment of millions of older women looking for a safe alternative to hormone replacement therapy, the largest study of its kind finds that one, daily dose of soy does not slow postmenopausal declines in physical and mental health.

While naturally occurring phytoestrogens found in soy may still be of benefit for younger women going through menopause, "women over the age of 60 aren't necessarily going to gain any benefit with regards to bone density, cholesterol-lowering effects or effects on memory," concluded study co-author Johanna Lampe, a nutritional biochemist at the Fred Hutchinson Cancer Research Center in Seattle.

The findings appear in the July 7 issue of the Journal of the American Medical Association..

Postmenopausal reductions in circulating estrogen raise risks for a variety of age-related conditions. For years, millions of American women fought back with hormone replacement therapy (HRT).

But in July 2002, a part of a large study called the Women's Health Initiative was halted prematurely after researchers found HRT raised risks for breast cancer, heart disease and stroke. With HRT suddenly in disfavor, women began to look for safer alternatives.

Enter soy, rich in naturally occurring estrogen-like compounds called isoflavones.

"It's become very popular," Lampe explained. "There were a number of small studies that had shown potential effects of soy on bone mineral density -- a risk factor for osteoporosis -- as well as effects on cholesterol levels, in men. So many women looking for alternatives to HRT are now turning to soy."

But has the recent hype surrounding soy outstripped reality? To find out, Lampe and a team of researchers led by Dr. Sanne Kreijkamp-Kaspers of the University Medical Center in Utrecht, the Netherlands, had 202 Dutch women aged 60 and older consume either 25 grams of soy protein or a non-soy milk powder daily for a period of one year.

The women were tested before and after the study to assess their bone mineral density, cholesterol levels and mental sharpness.

Unfortunately, according to Lampe, "soy had no effect on cholesterol levels, bone mineral density or any of the memory and mental acuity tests that were done."

She admits the researchers were "surprised" by the results, because smaller, less rigorous studies conducted in the past had suggested some benefit for postmenopausal women.

Still, "there actually hadn't been any studies done in any systematic fashion in older women," Lampe pointed out. All of the previous studies cited most often by either the scientific community or the media "had been done in earlier decades [of life]," when the study participants were in their late 40s or 50s, she said.

"It may have been a case of making generalizations to a wider age range than was necessarily appropriate," she said.

Soy may still be of benefit for younger women going through symptoms of menopause, especially for its ability to ease hot flashes and other problems. But for women over 60, the bean-based food appears to offer little benefit outside of healthy nutrition.

So where does this leave older women hoping to fight osteoporosis, high cholesterol and memory loss?

"I think this is something a woman really needs to discuss with her physician," Lampe said. "There are various medications that may be helpful, and, of course, lifestyle changes, too. Each woman has to decide which of these three conditions is a high priority for her, and make her decision based on that."

Dr. Thomas Clarkson, a researcher at Wake Forest University, has long studied soy's effects on postmenopausal health. He said he was not overly surprised by the Dutch findings, since his research in both animals and humans suggests that soy isoflavones only improve a woman's health through synergy with circulating estradiol, a female hormone.

"In the absence of estradiol, there is no effect," Clarkson said. Because women past the age of 60 retain only very small amounts of circulating estradiol, this could explain the Dutch results, he said. 

And because estradiol levels decline as menopause proceeds, soy may only be helpful in relieving menopausal symptoms early in the menopausal process. 

According to Clarkson, its ultimate role might be as a complementary --- not alternative -- therapy, "given alongside very low-dose estradiol therapy."