Click on the different areas of the male or female body to learn about the effects of soy.

Heart

Cardiovascular disease (CVD) is the leading cause of death in American women, killing almost 503,000 women in 1997 (most recent statistics available). Japanese women have a death rate from CVD that is less than half the rate in American women—85 in Japan versus 192 (deaths per 100,000 population) in the United States. One difference between Japanese and American women is the high intake of soyfoods in the traditional Japanese diet, compared to a very low soyfood intake in the United States. This has led researchers to investigate ways in which soy may help lower the risk of CVD.

Atherosclerosis–the development of plaque in the inner lining of the arteries–is the process underlying most CVD. The level in your blood of Low-Density Lipoprotein-cholesterol (LDL-cholesterol) that has undergone a damaging chemical reaction called oxidation is a major factor in the development of artery-clogging plaque.

Consumption of soy protein instead of animal protein reduces blood levels of LDL-cholesterol. Although some studies suggest that the isoflavones naturally occurring in soy may be responsible for its cholesterol-lowering effect, research has shown that purified isoflavone "pills" don't lower cholesterol in postmenopausal women. These findings suggest either that isoflavones are effective only when consumed in their natural state as combined with soy protein or that some other biologically active component of soy protein is responsible for its cholesterol-lowering effect. There also is evidence that soy protein retaining its isoflavones and other naturally occurring phytochemicals may—

• improve artery health
• reduce the amount of atherosclerotic plaque in arteries
• protect against oxidation of LDL-cholesterol
• reduce the tendency to form blood clots, which can complete the blocking of narrowed arteries

In October 1999 the U.S. Food and Drug Administration (FDA) authorized the use of a Health Claim stating that consuming 25 grams of soy protein per day, as part of a diet low in saturated fat and cholesterol, may lower the risk of coronary heart disease.

For more information, go to Cardiovascular Disease.

References
1. AHA (American Heart Association). 2000 Heart and Stroke Statistical Update. Dallas (TX):American Heart Association, 1999.

2. Anderson JW, Johnstone BM, Cook-Newell ME. Meta-analysis of the effects of soy protein intake on serum lipids. New England Journal of Medicine 1995;333:276-282.

3. Crouse JR III, Morgan T, Terry JG, et al. 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. Archives of Internal Medicine 1999;159:2070-2076.

4. Nestel PJ, Yamashita T, Sasahara T, et al. Soy isoflavones improve systemic arterial compliance but not plasma lipids in menopausal and perimenopausal women. Arteriosclerosis, Thrombosis, and Vascular Biology 1997;17:3392-3398.

5. Kapiotis S, Hermann M, Held I, et al. Genistein, the dietary-derived angiogenesis inhibitor, prevents LDL oxidation and protects endothelial cells from damage by atherogenic LDL. Arteriosclerosis, Thrombosis, and Vascular Biology 1997;17:2868-2874.

6. Honoré EK, Williams JK, Anthony MS, Clarkson TB. Soy isoflavones enhance coronary vascular reactivity in atherosclerotic female macaques. Fertility and Sterility 1997;67:148-154.

7. Wilcox JN, Blumenthal BF. Thrombotic mechanisms in atherosclerosis: potential impact of soy proteins. Journal of Nutrition 1995;125(suppl): 631S-638S.

8. Anthony MS, Clarkson TB, Bullock BC, Wagner JD. Soy protein versus soy phytoestrogens in the prevention of diet-induced coronary artery atherosclerosis of male cynomolgus monkeys. Arteriosclerosis, Thrombosis, and Vascular Biology 1997;17:2524-2531.

Breast

Breast cancer is the second leading cause of cancer death in American women and will result in an estimated 40,800 deaths in 2000. Japanese women have a death rate (deaths per 100,000 population) from breast cancer of 7.7, compared with a breast cancer death rate of 20.0 in American women.

This reduced risk of breast cancer doesn't appear to be genetic since it disappears as Asian women move to the West. One study found that in Chinese and Japanese women, the incidence of breast cancer was lowest in those living in Asia, intermediate in those born in Asia but living in the United States, and highest in Asian women born in the United States. Even in this last group, the incidence of breast cancer was appreciably lower than in American Caucasian women.

One factor thought to affect the risk of breast cancer is diet. Laboratory studies have shown that genistein, the major isoflavone in soy, inhibits the growth and multiplication of breast cancer cells. Soy isoflavones can be classified as phytoestrogens, and research has shown that phytoestrogens are associated with a substantial reduction in breast cancer risk. In several studies, consuming soy protein with isoflavones increased menstrual cycle length. In one of these studies, soy consumption also decreased the blood level of a very potent type of naturally occurring estrogen (17 ß-estradiol). The researchers suggested that both of these changes might account, at least in part, for the lower risk of breast cancer associated with soy consumption. Further dietary intervention studies using soyfoods are needed to investigate the possible role of soy in helping reduce the risk of breast cancer in women.

For more information, go to Cancer.

References
1. ACS (American Cancer Society). Cancer Facts & Figures 2000. Atlanta (GA):American Cancer Society, 2000.

2. Stanford JL, Herrinton LJ, Schwartz SM, Weiss NS. Breast cancer incidence in Asian migrants to the United States and their descendants. Epidemiology 1995;6:181-183.

3. Peterson G, Barnes S. Genistein inhibits both estrogen and growth factor-stimulated proliferation of human breast cancer cells. Cell Growth & Differentiation 1996;7:1345-1351.

4. Zava DT, Duwe G. Estrogenic and antiproliferative properties of genistein and other flavonoids in human breast cancer cells in vitro. Nutrition and Cancer 1997;27:31-40.

5. Shao Z-M, Wu J, Shen Z-Z, Barsky SH. Genistein exerts multiple suppressive effects on human breast carcinoma cells. Cancer Research 1998;58:4851-4857.

6. Ingram D, Sanders K, Kolybaba M, Lopez D. Case-control study of phyto-oestrogens and breast cancer. The Lancet 1997;350(9083):990-994.

7. Cassidy A, Bingham S, Setchell KDR. Biological effects of a diet of soy protein rich in isoflavones on the menstrual cycle of premenopausal women. American Journal of Clinical Nutrition 1994;60:333-340.

8. Lu L-J W, Anderson KE, Grady JJ, Nagamani M. Effects of soya consumption for one month on steroid hormones in premenopausal women: implications for breast cancer risk reduction. Cancer Epidemiology, Biomarkers & Prevention 1996;5:63-70.

Bones

About 80% of the estimated 28 million Americans who either have osteoporosis or who are at increased risk of developing this disabling disease are women. One major factor for developing the weak bones characteristic of osteoporosis is insufficient calcium intake and availability particularly early in life. A diet high in animal protein, such as is common in the United States, increases calcium excretion in urine leaving less for the body to use. However, research has shown that soy protein doesn't increase calcium excretion.

Soy protein with its naturally occurring isoflavones has been shown to have a positive effect on bone health in women. This is thought to be due in large part to the fact that isoflavones have some activities similar to the hormone estrogen, which is known to help protect against excessive breakdown of bone.

For more information, go to Bone Health.

References
1. NIH (National Institutes of Health). Osteoporosis overview. Accessed 6/2000.

2. Breslau NA, Brinkley L, Hill KD, Pak CYC. Relationship of animal protein-rich diet to kidney stone formation and calcium metabolism. Journal of Clinical Endocrinology and Metabolism 1988;66:140-146.

3. Potter SM, Baum JA, Teng H, et al. Soy protein and isoflavones: their effects on blood lipids and bone density in postmenopausal women. American Journal of Clinical Nutrition 1998;68(suppl):1375S-1379S.

Kidney

Kidney disorders affect more than 3 million Americans. Renal damage is most often a result of diabetes or high blood pressure. In addition, high blood levels of cholesterol and triglycerides can injure kidneys. Most people with chronic kidney disorders are prescribed a low-protein diet in order to decrease the workload of their kidneys and slow the progress of renal disease.

Some long-term studies have shown that consuming soy protein protects kidneys, while excessive amounts of animal protein harm the kidneys. In people with chronic kidney disease, a diet based on soy protein appears to have the same effect on kidney function as a low-protein diet of primarily animal protein, but with the important benefit of providing a higher amount of high-quality protein. In addition, substituting soy protein for animal protein has been shown to lower blood levels of cholesterol and triglycerides.

References

1. NIDDK (National Institute of Diabetes and Digestive and Kidney Diseases). Kidney and urologic diseases statistics for the United States. Accessed 6/00.

2. Anderson JW, Smith BM, Washnock CS. Cardiovascular and renal benefits of dry bean and soy intake. American Journal of Clinical Nutrition 1999;70(suppl):464S-474S. 3. Kontessis P, Jones S, Dodds R. et al. Renal, metabolic and hormonal responses to ingestion of animal and vegetable proteins. Kidney International 1990;38:136-144. 4. Anderson JW, Johnstone BM, Cook-Newell ME. Meta-analysis of the effects of soy protein intake on serum lipids. New England Journal of Medicine 1995;333:276-282.

Female Organs

More than 25,000 American women will die from cancers of the female organs in 2000—an estimated 14,000 from ovarian cancer, 6,500 from endometrial cancer, and 4,600 from cervical cancer. Although only limited research has investigated soy and cancers of the female reproductive tract, there are some positive indications.

Research has shown that the addition of genistein, the primary isoflavone in soy, increased the effectiveness of two cancer drugs (quercetin and tiazofurin) in inhibiting the growth of ovarian cancer cells in the laboratory. A study in women of different ethnic backgrounds living in Hawaii found that a diet low in fat, high in fiber, and rich in legumes (especially soybeans) and other plant foods reduced the risk of endometrial cancer.

For more information, go to Cancer.

References

1. ACS (American Cancer Society). Cancer Facts & Figures 2000. Atlanta (GA):American Cancer Society, 2000.

2. Shen F, Weber G. Synergistic action of quercetin and genistein in human ovarian cancer cells. Oncology Research 1997;9:597-602.

3. Li W, Weber G. Synergistic action of tiazofurin and genistein in human ovarian carcinoma cells. Oncology Research 1998;10:117-122.

4. Goodman MT, Wilkens LR, Hankin JH, et al. Association of soy and fiber consumption with the risk of endometrial cancer. American Journal of Epidemiology 1997;146:294-306.

Colon & Rectum

Colorectal cancer—cancer of the colon and/or rectum—is the third leading cause of cancer death in American women. It is estimated that colorectal cancer will kill 28,500 women in 2000.

A high-fiber diet is known to decrease the risk of colorectal cancer. This includes those soyfoods that retain their fiber, such as soybeans and soynuts. In addition, research has suggested an antioxidant effect for phytates such as are found in soy, making these substances potential anticancer agents. Although studies have shown soy isoflavones to be protective in several types of cancer, the evidence supporting a role in reducing the risk of colorectal cancer currently is limited.

For more information, go to Cancer.

References

1. ACS (American Cancer Society. Cancer Facts & Figures 2000. Atlanta (GA):American Cancer Society, 2000.

2. Segasothy M, Phillips PA. Vegetarian diet: panacea for modern lifestyle diseases? Quarterly Journal of Medicine 1999;92:531-544.

3. Graf E, Eaton JW. Suppression of colonic cancer by dietary phytic acid. Nutrition and Cancer 1993;19:11-19.

4. Messina M, Bennink M. Soyfoods, isoflavones and risk of colonic cancer: a review of the in vitro and in vivo data. Bailliére's Clinical Endocrinology and Metabolism 1998;12:707-728.

Menopause Management and Hot Flushes

All women who live long enough will someday reach menopause. The symptoms many women experience at menopause are eased by estrogen replacement therapy (ERT) or hormone replacement therapy (HRT). However, the vast majority of women in the United States,1 Europe, and Japan don't use either ERT or HRT.

Many women in Western countries experience similar symptoms at menopause, such as hot flashes, trouble sleeping, lack of energy, and headaches, among others. Large surveys of women in the United States, Canada, and Japan have shown that, with the exception of headache, these symptoms are much less common in Japanese than in Western women.

One basic difference between Japanese and Western women is the high intake of soyfoods in the traditional Japanese diet. Soy contains isoflavones , a type of phytochemical , which have some effects similar to estrogen. It has been suggested that soyfood consumption may contribute to the low incidence of hot flashes and various other menopausal symptoms in Japanese women.

One study in perimenopausal women showed that adding soy protein -to their diet twice a day decreased the severity of menopausal symptoms (in addition to lowering blood cholesterol levels and reducing blood pressure). In another study of postmenopausal women, adding soy protein daily resulted in a 45% reduction in the frequency of hot flashes by the end of 12 weeks, compared with a 30% reduction on placebo . Studies of the effect of "isoflavone pills" on menopausal symptoms have had mixed results. One study in postmenopausal women found that isoflavone pills made from a soy extract relieved hot flashes, while a study in breast cancer survivors showed that isoflavone pills were not effective in reducing hot flashes.

References

1. Salamone LM, Pressman AR, Seeley DG, Cauley JA. Estrogen replacement therapy. A survey of older women's attitudes. Archives of Internal Medicine 1996;156:1293-1297.

2. Schneider HPG. Cross-national study of women's use of hormone replacement therapy (HRT) in Europe. International Journal of Fertility 1997;42(suppl 2):365-375.

3. Nagata C, Matsushita Y, Shimizu H. Prevalence of hormone replacement therapy and user's characteristics: a community survey in Japan. Maturitas 1996;25:201-207.

4. Lock M. Menopause: lessons from anthropology. Psychosomatic Medicine 1998;60:410-419.

5. Washburn S, Burke GL, Morgan T, Anthony M. Effect of soy protein supplementation on serum lipoproteins, blood pressure, and menopausal symptoms in perimenopausal women. Menopause 1999;6:7-13.

6. Albertazzi P, Pansini F, Bonaccorsi G, et al. The effect of dietary soy supplementation on hot flushes. Obstetrics & Gynecology 1998;91:6-11.

7. Scambia G, Mango D, Signorile PG, et al. Clinical effects of a standardized soy extract in postmenopausal women: a pilot study. Menopause 2000;7:105-111.

8. Quella SK, Loprinzi CL, Barton DL, et al. Evaluation of soy phytoestrogens for the treatment of hot flashes in breast cancer survivors: a North Central Cancer Treatment Group Trial. Journal of Clinical Oncology 2000;18:1068-1074.