By Mark Messina, Ph.D.
Anyone even remotely familiar with soyfoods, or who casually reads this newsletter knows about the very provocative research suggesting soy may offer a number of health benefits including menopause symptom relief. While soybeans have much to offer from a nutritional perspective, it is because they contain isoflavones that so much attention is focused on this legume. And while the pace of isoflavone research has been steadily growing during the past three to four years, it seems that within just the past six months, there has been a quantum leap in interest in isoflavones among both the research community and consumers, as demand for isoflavone pills and soyfoods increases. It has become somewhat of a necessity for many health professionals to know something about soy/isoflavones.
As we seemingly reach a new high point on isoflavone research, it is appropriate to get perspectives from two pioneering researchers in this field. For the past ten years Dr. Stephen Barnes has been doing research on the mechanism of isoflavone action at the cellular level, but also has studied isoflavone pharmacokinetics. Dr. Kenneth Setchell has been doing isoflavone work for two decades. It can be said that this field started with his and his colleagues’ initial identification of isoflavones in the urine of laboratory animals. He has continued to conduct ground-breaking research, most notably recent papers on the effects of soy/isoflavones on menstrual cycle length and isoflavone levels in infants fed soy formula. Their contributions, along with those from countless other scientists form the basis for much of the information reported in this newsletter.
Isoflavones and Arterial Compliance
An Australian study of perimenopausal and postmenopausal women found isoflavone ingestion (80 mg/day) in the form of pills improved systemic arterial compliance by 26 percent, an improvement similar to that reported for estrogen (2). However, LDL-cholesterol oxidation was not inhibited. Systemic arterial compliance is a measure of the elasticity of the main conduit arteries and is considered to be an independent risk factor for heart disease. Thus, even in people with normal cholesterol, soybean isoflavones may help to reduce heart disease risk.
Soy and Hot Flashes
One symptom experienced by many women going through menopause is hot flashes. It has been proposed that the weak estrogenic effects of isoflavones will help to relieve menopause symptoms. To test this hypothesis, Italian researchers fed two groups of postmenopausal women either 60 grams of a powder (40 g of protein) composed primarily of casein or a similar amount containing soy protein (3). The number of hot flashes decreased in both groups; however, over the 12 weeks of the study, the hot flash incidence decreased by 45 percent in the soy group and by only 30 percent in the placebo or casein group. Other symptoms of menopause, such as insomnia, headaches and depression were not affected by soy. The amount of isoflavones provided by the soy powder is the amount found in about two servings of traditional soyfoods like tofu and soymilk.
For those interested in the full health benefits of soy isoflavones, newer naturally concentrated products are available with much better flavor than retail soy products. Because of a patented, natural concentration process, just 1 Revival Soy bar or shake contains the amount of isoflavones found in 6 cups of a typical soymilk. Learn more.
References 1. N Engl J Med 1997; 337:1641. 2. Arterioscler Thromb Vasc Biol 1997; 17:3392. 3. Obstet Gynecol 1997; 91: 6. 4. Nutr Cancer 1997; 29:1.
Reprinted with permission from The Soy Connection newsletter, Volume 6, No. 2, Spring 1998. More information about the newsletter can be obtained by writing to: Editor, The Soy Connection P.O. Box 237 Jefferson City, MO 65102
Isoflavone articles from The Soy Connection newsletter for registered dietitians, selected physicians and family and consumer science professionals.