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Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN
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INTRODUCTION |
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 TOP INTRODUCTION REFERENCES |
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Despite the growing body of data, effects of soy consumption on endogenous plasma hormones have been inconsistent, probably as a result of methodological differences in subject characteristics, study design and length, determination of menstrual cycle parameters, and isoflavone form and dose. Most reported studies have used randomized crossover or parallel-arm designs, although some studies have had no true control group or diet period. Soy has been provided as isolated soy protein (ISP), soy milk, textured vegetable protein (TVP), soy flour or soy foods; isoflavones have been consumed at levels of 7–200 mg/d, and the lengths of the diet periods have ranged from 2 wk to 6 mo.
The major effects in premenopausal women consuming 45–200 mg/d of
isoflavones in ISP, soymilk or TVP include decreased midcycle
luteinizing hormone and follicle-stimulating hormone concentrations
(Cassidy et al. 1994
and 1995
, Duncan et al. 1999a
); increased menstrual cycle length (Lu et al. 1996
); and decreased urinary estrogens, with a preferential
decrease in proposed genotoxic estrogen metabolites (Xu et al. 1998
). Increased menstrual cycle length and decreased urinary
estrogen excretion may suggest reduced exposure to estrogen, and both
have been associated with lowered risk of breast cancer. On the other
hand, soy consumption has been observed to both increase
(Petrakis et al. 1996
) and decrease (Lu et al. 1996
, Nagata et al. 1998
) plasma estrogen
concentrations; one study reported increased nipple aspirate volume
(Petrakis et al. 1996
), suggesting estrogenic effects on
the breast. Other observations include no effects on endometrial biopsy
results (Duncan et al. 1999a
) or plasma sex
hormone–binding globulin concentrations (Cassidy et al. 1994
and 1995
, Duncan et al. 1999a
, Nagata et al. 1998
, Petrakis et al. 1996
). These effects
appear to be due at least in part to the soy isoflavones (Duncan et al. 1999a
).
Few hormonal effects have been reported in postmenopausal women
consuming soy isoflavones. The major effects reported in postmenopausal
women consuming 34–165 mg/d of isoflavones in ISP, soy flour or soy
foods include increased sex hormone–binding globulin
(Brzezinski et al. 1997
, Duncan et al. 1999b
), a modest decrease in the frequency (Murkies et al. 1995
, Albertazzi et al. 1998
) and severity
(Brzezinski et al. 1997
, Washburn et al. 1999
) of hot flushes and vaginal dryness, and a slight increase
in vaginal cell maturation (Baird et al. 1995
,
Wilcox et al. 1990
). One study showed decreased
estrogens and no effects on endometrial biopsy results (Duncan et al. 1999b
). These results suggest that soy consumption
exerts modest estrogenic effects, likely as a result of the presence of
soy isoflavones.
Thus, soy consumption appears to exert modest hormonal effects in both pre- and postmenopausal women. The effects are generally in the direction of providing health benefits, although they are quite small and of uncertain clinical significance. Further research must be performed to clarify the magnitude and significance of the hormonal effects of soy consumption, and, if effects are seen, to establish whether the responsible components are the isoflavones or some other soy constituent.
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FOOTNOTES |
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REFERENCES |
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TOPINTRODUCTIONREFERENCES |
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1. Albertazzi P., Pansini F., Bonaccorsi G., Zanotti L., Forini E., De Aloysio D. The effect of dietary soy supplementation on hot flushes. Obstet. Gynecol. 1998;91:6-11[Abstract]
2.
Baird D. D., Umbach D. M., Lansdell L., Hughes C. L., Setchell K.D.R., Weinberg C. R., Haney A. F., Wilcox A. J., McLachlan J. A. Dietary intervention study to assess estrogenicity of dietary soy among postmenopausal women. J. Clin. Endocrinol. Metab. 1995;80:1685-1690
3. Brzezinski A., Adlercreutz H., Shaoul R., Rösler A., Shmueli A., Tanos V., Schenker J. G. Short-term effects of phytoestrogen-rich diet on postmenopausal women. Menopause 1997;4:89-94
4.
Cassidy A., Bingham S., Setchell K.D.R. Biological effects of a diet of soy protein rich in isoflavones on the menstrual cycle of premenopausal women. Am. J. Clin. Nutr. 1994;60:333-340
5. Cassidy A., Bingham S., Setchell K. Biological effects of isoflavones in young women: importance of the chemical composition of soyabean products. Br. J. Nutr. 1995;74:587-601[Medline]
6.
Duncan A. M., Merz B. E., Xu X., Nagel T. C., Phipps W. R., Kurzer M. S. Soy isoflavones exert modest effects in premenopausal women. J. Clin. Endocrinol. Metab. 1999a;84:192-197
7.
Duncan A. M., Underhill K. E. W., Xu X., Lavalleur J., Phipps W. R., Kurzer M. S. Modest hormonal effects of soy isoflavones in postmenopausal women. J. Clin. Endocrinol. Metab. 1999b;84:3479-3484
8. Lu L.-J.W., Anderson K. E., Grady J. J., Nagamani M. Effects of soya consumption for one month on steroid hormones in premenopausal women: implications for breast cancer risk reduction. Cancer Epidemiol. Biomark. Prev. 1996;5:63-70[Abstract]
9. Murkies A. L., Lombard C., Strauss B.J.G., Wilcox G., Burger H. G., Morton M. S. Dietary flour supplementation decreases post-menopausal hot flushes: effect of soy and wheat. Maturitas 1995;21:189-195[Medline]
10.
Nagata C., Takatsuka N., Inaba S., Kawakami N., Shimizu H. Effect of soymilk consumption on serum estrogen concentrations in premenopausal Japanese women. J. Natl. Cancer Inst. 1998;90:1830-1835
11. Petrakis N. L., Barnes S., King E. B., Lowenstein J., Wiencke J., Lee M. M., Miike R., Kirk M., Coward L. Stimulatory influence of soy protein isolate on breast secretion in pre- and postmenopausal women. Cancer Epidemiol. Biomark. Prev. 1996;5:785-794[Abstract]
12. Washburn S., Burke G. L., 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[Medline]
13. Wilcox G., Wahlqvist M. L., Burger H. G., Medley G. Oestrogenic effects of plant foods in postmenopausal women. Br. Med. J. 1990;301:905-906
14.
Xu X., Duncan A. M., Merz B. E., Kurzer M. S. Effects of soy isoflavones on estrogen and phytoestrogen metabolism in premenopausal women. Cancer Epidemiol. Biomark. Prev. 1998;7:1101-1108
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