Researchers Studying Potential of
Soy for Building Better Bones
By Kristina Goodnough
or years, Karen Prestwood of the Center on Aging has been treating women with osteoporosis, studying their fragile bones and testing ways to strengthen them. For just as long, Jane Kerstetter, an associate professor of dietetics, has been looking at dietary protein and its effects on calcium and bone activity.
Now the two women have joined forces to see whether soy protein can help build strong bones. Their study looks at whether incorporating just a couple of tablespoons of soy protein and its isoflavones in a woman's daily diet can increase bone strength and help prevent a hip fracture that could result in hospitalization and an end to independent living. To test their theory, Prestwood and Kerstetter are recruiting women over the age of 65 for a study of soy protein's effect on bone strength.
"The treatments we have for osteoporosis don't really work all that well," says Dr. Prestwood. "They don't do much to relieve the pain and there are lots of side effects. So I decided I needed to explore more possibilities." One of the possibilities that caught her eye was Kerstetter's work with soy and bone metabolism.
"Asians have fewer hip fractures, and their diets include larger amounts of soy than the average U.S. diet," Prestwood says. "That suggests soy may be beneficial to bone, but we need more well-controlled clinical trials to adequately test the theory."
Prestwood says soy contains isoflavones, which work on the same receptors as estrogen. It also has a molecular structure similar to estrogen. Her studies have demonstrated the positive effect on bone of lower and lower doses of estrogen, especially in older women.
"There's been an explosion in the number of women in this country who are increasing their consumption of soy products or isoflavone supplements, in an effort to use 'natural' treatments for chronic diseases," she says.
"There have been dozens of clinical studies that have shown a beneficial effect of soy protein on cholesterol levels; and the Food and Drug Administration has okayed claims that 25 mg of soy protein daily can decrease your risk of heart disease. But there have been only a few studies looking at soy's effect on bone, so it's not yet clear whether it's really beneficial for osteoporosis," Prestwood adds.
Kerstetter says soy is a complex food that is not particularly palatable to Westerners. "Most of us aren't really exposed to it," she says. She and Prestwood will give the women in the study straight, natural soy protein as a raw ingredient and teach them how to incorporate it into their diet.
For the most part, the women put it in hot cereal, juice, or soup. "It's a great thickener for soups," says Kerstetter, who also has worked with dieticians to develop a couple of muffin recipes that incorporate the soy protein.
The study, which is funded by the Department of Agriculture and the Brookdale Foundation in New York City, is designed to mimic the whole soybean and to test whether it's the soy protein or the isoflavones that provides the benefit, if any.
Participating women are assigned randomly to one of four groups. One group takes non-soy protein, plus a placebo. One takes the soy protein plus placebo. One takes non-soy protein plus 100 mg of isoflavones. The final group takes soy protein plus 100 mg of isoflavones. Blood and urine tests are used to determine bone activity.
"Our hypothesis is that soy protein with isoflavones will have the greatest benefit to bone," says Prestwood.
The three-month study is designed to iron out any kinks in subjects'
ability to tolerate the protein powder. Then Prestwood and Kerstetter will conduct another study that will last for one year. They hope that many of the women who participate in the pilot study will continue to participate in the longer study.
For information on taking part in the clinical trial, call the Health Center's General Clinical Research Center at (860) 679-3043.
Jane Kerstetter's Recipe for Banana Chocolate Chip Muffins Yields 12 muffins (each muffin contains two tablespoons of soy powder):
11/4 cups all-purpose flour
*** Although there are many soy products available, Kerstetter and Prestwood are using the soy protein isolate, the most highly processed form of the soybean consisting of 90-92 percent protein, so their study subjects get a lot of protein in a little volume. There are no known safety hazards associated with consuming soy protein isolate, says Kerstetter. She says it can be purchased online at the following sites: