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Effects of soy protein and isoflavones on circulating hormone concentrations in pre- and post-menopausal women: a systematic review and meta-analysis.

Hooper L, Ryder JJ, Kurzer MS, Lampe JW, Messina MJ, Phipps WR, Cassidy A - Hum. Reprod. Update (2009)

Bottom Line: In premenopausal women, meta-analysis suggested that soy or isoflavone consumption did not affect primary outcomes estradiol, estrone or SHBG concentrations, but significantly reduced secondary outcomes FSH and LH [by approximately 20% using standardized mean difference (SMD), P = 0.01 and 0.05, respectively].In post-menopausal women, there were no statistically significant effects on estradiol, estrone, SHBG, FSH or LH, although there was a small statistically non-significant increase in total estradiol with soy or isoflavones ( approximately 14%, SMD, P = 0.07, 21 studies).The clinical implications of these modest hormonal changes remain to be determined.

View Article: PubMed Central - PubMed

Affiliation: School of Medicine, Health Policy and Practice, University of East Anglia, Norwich NR4 7TJ, UK. l.hooper@uea.ac.uk

ABSTRACT
BACKGROUND Hormonal effects of soy and isoflavones have been investigated in numerous trials with equivocal findings. We aimed to systematically assess the effects of soy and isoflavones on circulating estrogen and other hormones in pre- and post-menopausal women. METHODS The Cochrane Library, MEDLINE and EMBASE (plus reviews and experts) were searched to December 2007. Inclusion of randomized or residential crossover trials of soy or isoflavones for 4 or more weeks on estrogens, SHBG, FSH, LH, progesterone and thyroid hormones in women was assessed independently in duplicate. Six percent of papers assessed were included. Data concerning participants, interventions, outcomes, potential effect modifiers and trial quality characteristics were extracted independently in duplicate. RESULTS Forty-seven studies (11 of pre-, 35 of post- and 1 of perimenopausal women) were included. In premenopausal women, meta-analysis suggested that soy or isoflavone consumption did not affect primary outcomes estradiol, estrone or SHBG concentrations, but significantly reduced secondary outcomes FSH and LH [by approximately 20% using standardized mean difference (SMD), P = 0.01 and 0.05, respectively]. Menstrual cycle length was increased by 1.05 days (95% CI 0.13, 1.97, 10 studies). In post-menopausal women, there were no statistically significant effects on estradiol, estrone, SHBG, FSH or LH, although there was a small statistically non-significant increase in total estradiol with soy or isoflavones ( approximately 14%, SMD, P = 0.07, 21 studies). CONCLUSIONS Isoflavone-rich soy products decrease FSH and LH in premenopausal women and may increase estradiol in post-menopausal women. The clinical implications of these modest hormonal changes remain to be determined.

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Related in: MedlinePlus

Funnel plot of results from included published studies on the effects of soy protein and isoflavones on circulating total estradiol (E2, pmol/l) in post-menopausal women.
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DMP010F4: Funnel plot of results from included published studies on the effects of soy protein and isoflavones on circulating total estradiol (E2, pmol/l) in post-menopausal women.

Mentions: In post-menopausal women, there was a small increase in circulating total estradiol concentrations following soy isoflavone consumption, but this was not statistically significant (on the basis of 21 studies, 580 women in combined control groups, SMD 0.13, 95% CI −0.01 to 0.27, or an increase of 14%, 95% CI −1% to +29%, P = 0.07, I2 29.3%), see Supplementary Fig. 1. Sensitivity analysis using MD was not statistically significant (MD 2.76 pmol/l, 95% CI −0.37 to 5.90), nor was the sensitivity analysis removing studies not assessed as at low risk of bias (SMD 0.17, 95% CI −0.07 to 0.41, eight studies, 231 in control groups, I2 37.7%), or that removing the underpowered crossover studies (SMD 0.15, 95% CI −0.02 to 0.32, P = 0.09, I2 39.2%). A funnel plot (Fig. 4) suggested that studies finding more extreme increases and decreases of estradiol following soy isoflavone intervention may be missing from the review. A further six studies (including 267 control participants) had analyzed the effect of soy isoflavones on total circulating estradiol in post-menopausal women, but not presented the data in a useable way—addition of the results of these studies could alter both the effect size and the statistical significance of the results of this meta-analysis.


Effects of soy protein and isoflavones on circulating hormone concentrations in pre- and post-menopausal women: a systematic review and meta-analysis.

Hooper L, Ryder JJ, Kurzer MS, Lampe JW, Messina MJ, Phipps WR, Cassidy A - Hum. Reprod. Update (2009)

Funnel plot of results from included published studies on the effects of soy protein and isoflavones on circulating total estradiol (E2, pmol/l) in post-menopausal women.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2691652&req=5

DMP010F4: Funnel plot of results from included published studies on the effects of soy protein and isoflavones on circulating total estradiol (E2, pmol/l) in post-menopausal women.
Mentions: In post-menopausal women, there was a small increase in circulating total estradiol concentrations following soy isoflavone consumption, but this was not statistically significant (on the basis of 21 studies, 580 women in combined control groups, SMD 0.13, 95% CI −0.01 to 0.27, or an increase of 14%, 95% CI −1% to +29%, P = 0.07, I2 29.3%), see Supplementary Fig. 1. Sensitivity analysis using MD was not statistically significant (MD 2.76 pmol/l, 95% CI −0.37 to 5.90), nor was the sensitivity analysis removing studies not assessed as at low risk of bias (SMD 0.17, 95% CI −0.07 to 0.41, eight studies, 231 in control groups, I2 37.7%), or that removing the underpowered crossover studies (SMD 0.15, 95% CI −0.02 to 0.32, P = 0.09, I2 39.2%). A funnel plot (Fig. 4) suggested that studies finding more extreme increases and decreases of estradiol following soy isoflavone intervention may be missing from the review. A further six studies (including 267 control participants) had analyzed the effect of soy isoflavones on total circulating estradiol in post-menopausal women, but not presented the data in a useable way—addition of the results of these studies could alter both the effect size and the statistical significance of the results of this meta-analysis.

Bottom Line: In premenopausal women, meta-analysis suggested that soy or isoflavone consumption did not affect primary outcomes estradiol, estrone or SHBG concentrations, but significantly reduced secondary outcomes FSH and LH [by approximately 20% using standardized mean difference (SMD), P = 0.01 and 0.05, respectively].In post-menopausal women, there were no statistically significant effects on estradiol, estrone, SHBG, FSH or LH, although there was a small statistically non-significant increase in total estradiol with soy or isoflavones ( approximately 14%, SMD, P = 0.07, 21 studies).The clinical implications of these modest hormonal changes remain to be determined.

View Article: PubMed Central - PubMed

Affiliation: School of Medicine, Health Policy and Practice, University of East Anglia, Norwich NR4 7TJ, UK. l.hooper@uea.ac.uk

ABSTRACT
BACKGROUND Hormonal effects of soy and isoflavones have been investigated in numerous trials with equivocal findings. We aimed to systematically assess the effects of soy and isoflavones on circulating estrogen and other hormones in pre- and post-menopausal women. METHODS The Cochrane Library, MEDLINE and EMBASE (plus reviews and experts) were searched to December 2007. Inclusion of randomized or residential crossover trials of soy or isoflavones for 4 or more weeks on estrogens, SHBG, FSH, LH, progesterone and thyroid hormones in women was assessed independently in duplicate. Six percent of papers assessed were included. Data concerning participants, interventions, outcomes, potential effect modifiers and trial quality characteristics were extracted independently in duplicate. RESULTS Forty-seven studies (11 of pre-, 35 of post- and 1 of perimenopausal women) were included. In premenopausal women, meta-analysis suggested that soy or isoflavone consumption did not affect primary outcomes estradiol, estrone or SHBG concentrations, but significantly reduced secondary outcomes FSH and LH [by approximately 20% using standardized mean difference (SMD), P = 0.01 and 0.05, respectively]. Menstrual cycle length was increased by 1.05 days (95% CI 0.13, 1.97, 10 studies). In post-menopausal women, there were no statistically significant effects on estradiol, estrone, SHBG, FSH or LH, although there was a small statistically non-significant increase in total estradiol with soy or isoflavones ( approximately 14%, SMD, P = 0.07, 21 studies). CONCLUSIONS Isoflavone-rich soy products decrease FSH and LH in premenopausal women and may increase estradiol in post-menopausal women. The clinical implications of these modest hormonal changes remain to be determined.

Show MeSH
Related in: MedlinePlus