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SOY PROTEIN AND SOY ISOFLAVONES

 

There is a growing body of literature on the beneficial effects of soy and soy isoflavones on cardiovascular disease, osteoporosis, cancer prevention and menopausal symptoms. It has been postulated that differences in the incidence of these disease states may be attributable to the difference in soy intake in the Asian and Western diet. Proposed mechanisms include reduced lipid peroxidation and increased resistance of LDL to oxidation. Oxidative damage to lipids may be involved in the etiology of atherosclerosis, cardiovascular disease in general, and cancer. Protein quality and quantity impact glucose and the insulin response curve, especially important in diabetics and hypoglycemics.

Administration of soy isoflavones has been shown to improve arterial compliance in menopausal females (arterial compliance diminishes in postmenopausal females, and diminished compliance leads to increased systolic blood pressure and possibly work of the left ventricle of the heart). Reports also reveal variable improvements in HDL, total cholesterol/HDL, and LDL/HDL in pre-and post-menopausal females and males both with normal and elevated plasma lipids.

It has been suggested that consumption of soyfoods may contribute to the relatively low rates of breast, colon and prostate cancers in Asian countries. The FDA now recommends 25 grams of soy be added to the daily diet. Proposed mechanisms of action include antiestrogenic activity by competing with estrogen for estrogen receptors; the isoflavone genistein is a specific inhibitor of protein tyrosine kinases; it also inhibits DNA topoisomerases. In premenopausal women soy protein suppressed midcycle surges of FSH and LH, resulting in increased plasma estradiol in the follicular phase and decreased cholesterol, effects similar to those of tamoxifen. This may explain in part the low incidence of breast cancer in Japanese and Chinese women. In murine bladder tumors soy products have been shown to reduce angiogenesis, increase apoptosis, and slightly reduce proliferation while showing no histopathological effects on the normal bladder mucosa.

Soy isoflavone extract was effective in reducing frequency and severity of flushes and did not stimulate the endometrium. Soy isoflavone extracts provide an attractive addition to the choices available for relief of hot flushes. Neither isoflavones nor soy exert clinically important estrogenic effects on vaginal epithelium or endometrium. This is particularly important for women who suffer from fibroids and cannot take estrogen replacement. Black cohosh is also a safe, effective alternative to estrogen replacement therapy for those patients in whom estrogen replacement therapy is either refused or contraindicated.

In humans the soy isoflavone ipriflavone has been shown to inhibit bone loss in the lumbar spine. Soy protein decreases calcium excretion. In rats it has been demonstrated to enhance bone formation, but this has not yet been confirmed in human studies.

References

Overview

Spiller GA et al. Effect of protein dose on serum glucose and insulin response to sugars. Am J Clin Nutr 1987;46:474-80.

Brandi, ML. Natural and synthetic isoflavones in the prevention and treatment of chronic diseases. Calcif. Tissue Int 1997; 61 Suppl 1:S5-8.

Messina, MJ. Legumes and soybeans: overview of their nutritional profiles and health effects. Am J Clin Nutr 1999 Sep; 70(3):439S-450S.

Anderson, JJ et al. Health potential of soy isoflavones for menopausal women. Public Health Nutr 1999 Dec;2(4):489-504.

Hardy ML. Herbs of special interest to women. J Am Pharm Assoc (Wash)2000 Mar-Apr;40(2):234-42.

Wiseman H et al. Isoflavone phytoestrogens consumed in soy decrease F(2)-isoprostane soncentrations and increase resistance of low-density lipoprotein to oxidation in humans. Am J Clin Nutr 2000 Aug;72(2):395-400.

Cardiovascular disease

Lichtenstein, AH. Soy protein, isoflavones and cardiovascular disease risk. J Nutr 1998 Oct; 128(10): 1589-92

Baum, JA et al. Long-term intake of soy protein improves blood lipid profiles and increases mononuclear cell low-density-lipoprotein receptor messenger RNA in hypercholesterolemic, postmenopausal women. Am J Clin Nutr 1998 Sep; 68(3):545-51.

Nestel, PJ et al. Isoflavones from red clover improve systemic arterial compliance but not plasma lipids in menopausal women. J Clin Endocrinol Metab 1999 Mar; 84(3):895-8.

Crouse JR et al A randomized trail comparing the effect of casein with that of soy protein containing variable amounts of isoflavones on plasma concentrations of lipids and lipoproteins. Arch Intern Med 1999 Sep 27;159(17):2070-6.

Samman S et al. The effect of supplementation with isoflavones on plasma lipids and oxidisability of low density lipoprotein in premenopausal women. Atherosclerosis 1999 Dec;147(2):277-83.

Merz-Demlow BE et al. Soy isoflavones improve plasma lipids in normocholesterolemic, premenopausal women.

Am J Clin Nutr 2000 Jun;71(6):1462-9

Lissin, LW et al. Phytoestrogens and cardiovascular health. J Am Coll Cardiol 20000 May;35(6):1403-10.

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Cancers

Messins MJ et al. Soy intake and cancer risk: a review of the in vitro and in vivo data. Nutr Cancer 1994;21(2):113-31.

Cassidy A et al. Biological effects of a diet of soy protein rich in isoflavones on the menstrual cycle premenopausal women. Am J Clin Nutr 1994 Sep;60(3):333-40.

Stoll BA. Eating to beat breast cancer: potential role for soy supplements. Ann Oncol 1997 Mar;8(3):223-5.

Zhou JR et al. Inhibitioin of murine bladder turorigenesis by soy isoflavones via alteration in the cell cycle, apoptosis, and angiogenesis. Cancer Res 1998 Nov 15;58(22):5231-8.

Moyad MA. Soy, disease prevention and prostate cancer. Semin Urol Oncol 1999 May;17(20;97-102.

Lamartiniere CA. Protection against breast cancer with genistein: a component of soy. Am J Clin Nutr 2000 Jun;71(6 Suppl):1705S-7S.

Lu LJ et al. Decreased ovarian hormones during a soya diet: implications for breast cancer prevention. Cancer Res 2000 Aug 1;60(15):4112-21.

Su SJ et al. The potential of ssoybean foods as a chemopreventive approach for human urinary tract cancer. Clin Cancer Res 2000 Jan;6(1):230-6.

Menopausal symptoms

Lieberman S. A review of the effectiveness of Cimicifuga racemosa (black cohosh) for the symptoms of menopause. J Womens Health 1998 Jun;7(5):525-9.

Seidl MM et al. Alternative treatments for menopausal symptoms. Systematic review of scientific and lay literature. Can Fam Physician 1998 Jun;44:1299-308.

Duncan Am et al. J Clin Endocrinol Metab 1999 Oct;84(10):3479-84.

Washburn S et al. Effect of soy protein supplementation on serum lipoproteins, blood pressure, and menopausal symptoms in perimenopausal women. Menopause 1999 Spring;6(1):7-13.

Upmalis DH et al. Vasomotor symptom relief by soy isoflavone extract tablets in postmenopausal women: a multicenter, double-blind, randomized, placebo-controlled study. Menopause 2000 Jul;7(4):236-242.

Osteoporosis

Arjmandi BH et al. Am J Clin Nutr 1998 Dec;68(6Suppl):1358S-1363S.

Head KA. Ipriflavone: an important bone-building isoflavone. Altern Med Rev 1999 Feb;4(1):10-22.

Scheiber MD et al. Isoflavones and postmenopausal bone health: a viable alternative to estrogen therapy? Menopause 1999 Fall;6(3):233-41.

Alekel DL et al. Isoflavone-rich soy protein isolate attenuates bone loss in the lumbar spine of perimenopausal women. Am J Clin Nutr 2000 Sep;72(3):844-52.

Messina M et al. Soyfoods, soybean isoflavones, and bone health: a brief overview. J Ren Nutr 2000 Apr;10(2):63-8.

 

 

 

 

 

 

 

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Last modified: June 04, 2005