Seeking soy as alternative to hormones

09/03/2002
By Rita Rubin, USA TODAY

Interest in alternatives to hormone replacement therapy, or HRT, is at an all-time high thanks to discouraging findings revealed in July from a government study of estrogen plus progestin.

"What are you doing for patients who refuse HRT?" the makers of Revival, "doctor-formulated soy protein," ask on their Web site in bold type.

Thanks in large part to women's worries about taking hormones, soy, which contains plant estrogens, is hot, much like oat bran was in the 1980s. Remember oat-bran-fortified pretzels?

Some companies "will put just enough soy in their product so they can splash 'soy' across the front of it," bemoans Bob Beeley, chairman of Houston-based Dixie USA, maker of soy foods.

Soy food and supplement companies would like postmenopausal women to think that their products provide the benefits of hormones without any risks.

In truth, soy's impact on hot flashes and other symptoms appears to be slight at best, and there is not yet any evidence that soy protects against fractures. Research suggests that soy foods might help reduce heart disease risk, but their effect on breast cancer risk isn't yet clear.

"A woman who is not going to take HRT will probably get some benefit from consuming soy," says Mindy Kurzer, a nutrition professor at the University of Minnesota-St. Paul. "But it's not going to be equivalent to HRT in the areas that HRT is beneficial."

Women who can't stomach soy milk or tofu shouldn't assume they can get the same benefit from popping a pill containing isoflavones, the plant estrogens in soy, Kurzer cautions.

Hundreds of studies using soy protein and foods have been done, but "we know very little about the effects of purified isoflavones themselves," she says. "The manufacturers are way ahead of the science."

Estrogen for menopause symptoms

Soy does seem like a logical alternative to conventional HRT. In Japan, where people routinely eat one or two servings of soy a day, women are much less likely to report having menopause symptoms than women in the USA, where the main source of soy has been fake bacon bits. Japanese women also have lower rates of heart disease, breast cancer and fractures.

But it's difficult to tease out soy's effects from other aspects of the Japanese diet, notes Gregory Burke, chair of public health sciences at Wake Forest University School of Medicine in Winston-Salem, N.C. On average, the Japanese consume fewer calories and drink more green tea than Americans, both factors thought to protect against heart disease and possibly cancer.

Observational studies, such as those linking soy intake to Japan's lower death rates, are the same type of research that led doctors to believe that hormones protected against heart disease.

It took the huge government study to dispel that notion, at least regarding Prempro, the top-selling brand of estrogen plus progestin. In the study, researchers randomly assigned 16,608 women to take either Prempro or a placebo. (Randomized trials of soy have enrolled only a few hundred at most.)

After four years, the women on Prempro had a higher risk of heart disease, breast cancer, blood clots and strokes. They were less likely to break a bone or develop colon cancer, but those benefits did not outweigh the risks, researchers say. Still, the risk/benefit ratio probably tips in favor of short-term estrogen use in women with severe menopausal symptoms, scientists say.

Nothing beats estrogen for cooling hot flashes.

"I am completely not impressed by the ability of isoflavones to relieve hot flashes," says Mark Messina, a Port Townsend, Wash., nutrition researcher who consults for makers of soy foods and supplements. Messina says he tells women: "You're going to be the first to know if it works. You can try it. Mostly, it's going to be a placebo effect."

Over time, Kurzer notes, menopause symptoms usually subside, and women may mistakenly credit soy.

Soy intake under study

As in the case of hot flashes, if soy does have a beneficial effect on bone, it's probably weaker than conventional hormones' effect, says Donna Kritz-Silverstein, family and preventive medicine professor at the University of California School of Medicine in San Diego.

In the Journal of Women's Health & Gender-Based Medicine this year, Kritz-Silverstein and Deborah Goodman-Gruen reported that postmenopausal women who ate a lot of soy had greater bone density in their spine than women who didn't.

After surveying the 208 women about their soy intake, the researchers randomly assigned one-half to two packets of soy powder a day to mix in drinks. Each packet contained 100 calories and 45 milligrams of isoflavones. The other women were given identical-looking packets with a powder that did not contain soy. Kritz-Silverstein and Goodman-Gruen are now analyzing data from their two-year study to see if soy had any effect on bone.

Enough clinical trial data existed in 1999 to convince the Food and Drug Administration that soy favorably affects cholesterol and triglyceride levels, at least in people with high levels. So the agency said makers of foods containing soy protein could claim that eating 25 grams each day might lower heart disease risk.

Despite what isoflavone supplement makers would like you to believe, it appears that only whole soy protein benefits cholesterol and triglyceride levels, says Thomas Clarkson, a professor of comparative medicine at Wake Forest.

Clarkson's research has focused mainly on postmenopausal monkeys, which he says are "probably highly predictive" of what would happen in humans. While whole soy protein lowered the monkeys' LDL (bad cholesterol) and raised their HDL (good cholesterol), soy protein that had its isoflavones removed had no effect. But adding isoflavones back to soy does not restore its ability to lower LDL and raise HDL.

Isoflavone pills probably have "no value whatsoever" for cholesterol or triglycerides, Clarkson says.

Whole soy also might inhibit heart disease in other ways, such as by acting as an antioxidant and increasing arteries' elasticity, he says.

Scientists still are trying to define the effect of soy or isoflavones on breast cancer. Japanese women have less breast cancer than those in the USA, but that seems to be linked to lifelong soy intake, Messina says. Adding soy or isoflavone supplements to the diet in middle age, especially in large quantities, might cause tumors in women who have breast cancer or are at high risk for the disease, some researchers say.

That's why, says Judith Balk, assistant research professor at the University of Pittsburgh School of Medicine, "if somebody had breast cancer and they said, 'I want to start eating a lot of soy,' I wouldn't recommend that."