Soy Foods for Womens Health

By Marcia Zimmerman, M.Ed., C.N.

Gloria remembers the exact day menopause hit. It was, in her own words, "major menopause meltdown." And like so many late "baby boomer" moms, Gloria's menopause arrived at fifty-two, just as her daughter turned fifteen. "Those were grim times, " she recalls. "Her raging hormones clashed with my heat surges - until we both spiraled out of control - finally dissolving into two emotional heaps." No permanent damage was done, and the two women are now best friends. However, Gloria's daughter Jan told me recently that she is not looking forward to her own menopausal "rite of passage."

By the year 2015 approximately half of all American women will be menopausal. And, assuming current trends continue, nearly half of them will not begin the highly recommended hormone replacement therapy or HRT. This is either because their symptoms are mild causing little discomfort, or they resist taking medication for a natural condition. And, among those who do opt for HRT, one in three will discontinue its use by the end of the first year - most because of unwanted weight gain and fear of increased cancer risk.

The wonderful freedom that comes from retiring one's tampons brings a new set of problems. The sudden onset of dramatic changes leave us feeling like we're occupying someone else's body. And we must acknowledge an increased risk of heart disease and bone loss that estrogen has protected us from all our adult lives. Women will spend about a third of their lives - some of the best years - post-menopause. And, we can protect our hearts and prevent bone loss by adopting some good dietary practices. Let's begin with menopausal symptoms.

Menopause Symptoms and Soy foods

Hot flashes are the most common signal that menopause has arrived. For some women the flushes are mild - a rather pleasant warm rush that radiates from the center of the body. Other women turn beet red and begin to perspire excessively, an embarrassing occurrence, especially in front of male colleagues. Some even lose sleep as night sweats soak the bed. Irritability, slowed cognitive response, lowered immune resistance, spotting or irregular periods and fatigue may also mark the menopausal transition.

A healthy attitude about the transition into a new phase of life, thoughtful self assessment and a rearranging of priorities are imperative to moving smoothly through this passage. Reducing caffeine, alcohol consumption and use of hot, spicy foods will reduce hot flashes. Adding soy foods to your diet will also reduce flushes and these marvelous legumes will also protect your heart, reduce bone loss and help prevent cancer.(Knight)

Soy foods are rich in phytoestrogen isoflavones called genistin and daidzin that the body converts into the biologically active forms genistein and daidzein. What's amazing about phytoestrogens is they are stand-ins for estrogen binding to the same cellular receptors as estrogen. These receptors are located all over the body - brain, bones, heart and blood vessels which explains why menopausal symptoms involve so many systems. While phytoestrogens mimic the effects of estrogen they are weaker in action and consequently don't cause the same problems.(Setchell)

Moreover, soy isoflavones are dual-action - substituting for estrogen when levels are low and crowding out surplus estrogen that could cause hormone imbalances and even cancer. Consequently, soy foods benefit women both before and after menopause. As estrogen levels diminish during menopause, phytoestrogens partially take up the slack, giving cells important signals that keep bone tissue healthy and heart and blood vessels working smoothly. (Knight) Phytoestrogens also orchestrate cellular resistance to progression of cancer by blocking the effects of high estrogen levels. (TFL, April)

It doesn't take a lot of soy foods to raise phytoestrogen levels in blood serum. Scientists have determined that one serving of soy milk, 8 ounces of tofu or cup of roasted soy nuts are enough to elicit an estrogenic response. (Helferich) As for hot flashes, studies in the US and Europe suggest that sixty grams of soy protein powder taken daily for ninety days significantly reduced hot flashes.(Washburn) What about protection against heart disease and osteoporosis?

Cardiovascular benefits of soy foods have been well researched and documented. One of the most recent was a study completed in 1999 in which women with high cholesterol levels were given sixty grams of soy protein containing two levels of isoflavones, either 1.39 mg or 2.25 mg. After six months, both levels of isoflavones raised HDL (good) cholesterol, They increased the number of LDL (bad) cholesterol receptors in white blood cells, a positive indicator it was being eliminated, vital to improved cardiovascular health. (Baum, Crouse) Isoflavones are also efficient anti-oxidants and may reduce free-radical attack on blood vessel walls - a precipitating event in atherosclerosis. Much more on CVD benefits can be found in TFL's April issue.

Osteoporosis and Soy foods -The solid appearance of bones belies a bustling interior. Underneath lies a vast network of bone tissue in a constant flux of rebuilding and breakdown. Although the greatest bone density develops before the age of thirty, the process continues throughout life. Bone tissue turnover or "remodeling" gets rid of old bone cells and lays down new ones. Many nutrients are needed to nurture this process., among them calcium, magnesium, potassium, manganese, boron, vitamins C, D, K and omega-3 fatty acids.

Orchestrating the process is estrogen which keeps a woman's bones dense during her child bearing years. Following menopause when estrogen levels fall quickly, remodeling shifts from bone building to bone loss at an increased rate. During the first years following menopause, up to 10% of bone mass is lost per year. The loss tapers off after five years as other hormone adjustments occur. However, the bone loss is not easy to reverse and is one of the chief reasons hormone replacement therapy is advised by doctors. (Scheiber)

Recent scientific evidence has shown that eating soy foods not only slows bone loss but even helps rebuild bone structure. Researchers at the University of Illinois, Urbana-Champaign found that post-menopausal women who ate daily servings of 60 grams of soy protein containing 2.25 mg isoflavones for six months were protected against spinal bone loss.(Potter) Moreover, animal research has shown that isoflavones do not increase uterine activity, a cancer concern and making isoflavones a better option than HRT. (Ishimi) Italian researchers attribute the multiple health effects of isoflavones which include bone sparing, to the mixed weak estrogenic and anti-estrogenic effects. (Brandi, Abertazzi)

The research is so compelling that soy isoflavones have become the newest trendy bone savers. It takes a little more soy to get bone building benefits. Experts advise you should have daily servings of 90 mg of isoflavones - the amount in 2 ounces of soy protein powder; cup roasted soy nuts or 8 ounces of tofu, both mentioned above. Or, you can look for supplements of ipriflavone.

Ipriflavone an isoflavone derived from daidzein that has been widely studied in humans and has been found to halt bone loss and increase bone formation. It is very effective and possesses virtually no side effects. Besides bone loss, ipriflavone may be useful in treating bone loss from other causes such as overuse of steroids, removal of the ovaries and parathyroid gland disorders. (Head) Although you won't find it naturally occurring in soy foods, ipriflavone supplements may helpful if you do suffer from bone loss.

Vaginal dryness is a complaint among some women, more often several years after they have gone through menopause. While soy's effects seem to be modest, some investigators have reported changes in the vaginal walls of women who were consuming soy protein with isoflavones. And, while we don't want to hold out false hopes for you, don't be surprised if you notice some improvement. (Duncan, Baird)

The Menstrual Cycle and Soy foods

The menstrual cycle consists of two phases. The follicular phase occurs between menstruation and ovulation and the luteal phase from ovulation to menstruation. During the first phase (14 to 17 days), estrogen levels gradually rise along with other hormones that ready the ovary to release an ovem. Between ovulation and menstruation (14 days) these hormones drop and progesterone rises to prepare the uterus for pregnancy - should conception occur. If it doesn't, progesterone levels also drop and menstruation follows. The average cycle repeats every twenty-eight days, but both longer and shorter cycles are normal.

Scientists have found that soy protein (60 g a day with 45 mg isoflavones) lengthen the follicular phase, resulting in fewer cycles per year and fewer estrogen "surges." Over a lifetime, this can make a huge difference in how much estrogen breast tissue is exposed to. This may be one reason why Asian women are less likely to get breast cancer, and a good one for including soy foods in the diet. (Cassidy, Setchell) And, while this is not considered the primary mechanism by which isoflavones prevent breast cancer, the phytoestrogen effects of soy include lessening pre-menstrual syndrome or PMS. (Xu)That's because isoflavones smooth out hormone imbalances among pre-menopausal women. (Duncan) It appears that the earlier girls and young women are exposed to phytoestrogens, the more protective benefits they can hope to enjoy.(Stephens)

Soy foods in Early Life

The health benefits of soy foods are becoming very well known and it seems the sooner they are introduced into the diet, the better. This has led scientists to investigate the benefits soy foods might have on fetal hormone development. Mothers eating soy foods may be passing multiple benefits on to their unborn child. And, these benefits may continue during breast feeding. (Jerman) Researchers are also studying the possible protection against later development of osteoporosis among babies fed soy formula instead of the typical milk-based preparation.

For teens, eating soy foods may help develop bone density. As peak bone density occurs before the age of thirty, early consumption of soy foods might be good insurance against later bone thinning. (Reuters) §

References: ♦ A review of the clinical effects of phytoestrogens by DC Knight (Obstetrics and Gynecology, May 1996)  ♦ Soybean isoflavones: metabolism and physiology by KD Setchell (First International Symposium on the Role of Soy in Preventing and Treating Chronic Disease Feb 1994)  ♦ Food phytoestrogens: an abundance of weak estrogen agonists by Willian Helferich (Fundamental and Applied Toxicology, 1997)  ♦ "Effect of soy protein supplementation on serum lipoproteins, blood pressure and menopausal symptoms in perimenopausal women" by S Washburn et al Menopause, spring 1999.  ♦ "Long-term intake of soy protein improves blood lipid profiles and increases mononuclear cell low-density-lipoprotein receptor messenger RNA in hypercholesterolemic, postmenopausal women" By JA Baum Am J Clin Nutr Sep 1998   ♦ A randomized trial comparing the effect of casein with that of soy protein containing varying amounts of isoflavones on plasma concentrations of lipids and lipoproteins by JR Crouse (Arch Intern Med Sep 1999)  ♦ Isoflavones and postmenopausal bone health: a viable alternative to estrogen therapy? by MD Scheiber (Menopause, Fall, 1999)  ♦ Soy protein and isoflavones: their effects on blood lipids and bone density in postmenopausal women. by SM Potter et al Am J Clin Nutr Dec. 1998  ♦ Selective effects of genistein, a soybean isoflavone, on B-lymphopoiesis and bone loss caused by estrogen deficiency By Y. Ishimi et al (Endocrinology, Apr. 1999)  ♦ Natural and synthetic isoflavones in the prevention and treatment of chronic diseases by ML Brandi (Calcif Tissue Int 1997)  ♦ Dietary soy supplementation and phytoestrogen levels by P Albertazzi et al. Obstet. Gynecol (Aug 1999)  ♦ The effect of dietary soy supplementation on hot flushes by P Albertazziet al. Obstet Gyecol (Jan 1998)  ♦ Ipriflavone, an important bone-building isoflavone by KA Head (Altern Med Rev Feb. 1999)  ♦ Dietary intervention study to assess estrogenicity of dietary soy among postmenopausal women by DD Baird (J Clin Endocrinol Metab May, 1995)  ♦ Biological effects of a diet of soy protein rich in isoflavones on the menstrual cycle of premenopausal women by A Cassidy (Am J Clin Nutr Sep 1994)  ♦ Effects of soy isoflavones on estrogen and phytoestrogen metabolism in premenopausal women by X XU (Cancer Epdidemiol Biomarkers Dec 1998)  ♦ Soy isoflavones exert modest hormonal effects in premenopausal women by AM Duncan et al (J Clin Endocrinol Metab Jan 1999)  ♦ Breast Cancer: anetiological factors and associations (a possible protective role of phytoestrogens by FO Stephens (Aust N Z J Surg Nov 1997)  ♦ Diet High In Soy Benefits Fetus by Rebecca Jerman (Medical Tribune 1999)  ♦ Pediatric Nutrition Linked to Adult Osteoporosis (Reuters Medical News, 1999) 

Copyright©, 2001 by The Zimmerman Group, Inc. All rights reserved. Except as permitted under the Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher.

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