Elsevier

Nutrition

Volume 29, Issue 1, January 2013, Pages 8-14
Nutrition

Review
Soy isoflavone supplementation could reduce body weight and improve glucose metabolism in non-Asian postmenopausal women—A meta-analysis

https://doi.org/10.1016/j.nut.2012.03.019Get rights and content

Abstract

Objective

The objective of this study was to conduct a systematic review and a meta-analysis to confirm the effects of soy isoflavone supplementation on body weight, fasting glucose, and insulin level in non-Asian postmenopausal women.

Methods

We searched the PubMed, EMBASE, and Cochrane databases up to October 2010 for randomized controlled trials regarding the effects of isoflavone supplementation on body weight, fasting glucose, and insulin level. Pooled estimates and 95% confidence intervals (CIs) were calculated by the fixed-and-random-effects model.

Results

Nine studies with 528 participants for body weight, 11 studies with 1182 participants for fasting glucose, and 11 studies with 1142 participants for fasting insulin were included, respectively. Significant reductions were found in body weight [weighted mean difference (WMD), −0.515; 95%CI: −0.895 to −0.134; P = 0.008), glucose level (WMD, −0.189; 95%CI: −0.344 to −0.033), and fasting insulin level (WMD, −0.940; 95%CI: −1.721 to −0.159) with soy isoflavone supplementation compared with placebo control group in non-Asian postmenopausal women after adjusted by unpublished studies. Furthermore, isoflavone supplementation in shorter duration (<6 mo) could significantly reduce body weight (WMD, −0.506; 95%CI: −0.888 to −0.124; P = 0.009) and longer duration (≥6 mo) could significantly reduce blood glucose in postmenopausal women (WMD, −0.270; 95%CI: −0.430 to −0.110; P = 0.001). Meanwhile, more reduction in body weight was observed in the lower dose subgroup (dose < 100 mg). Moreover, it is more effective to reduce body weight and fasting insulin level with soy isoflavone supplementation in normal weight (body mass index < 30) than obese (body mass index ≥ 30) women.

Conclusions

This meta-analysis showed soy isoflavone supplementation could be beneficial for body weight reduction, glucose, and insulin control in plasma. Large and well-designed studies are recommended to confirm this conclusion.

Introduction

After menopause, the incidence of cardiovascular disease (CVD) and metabolic diseases increases significantly, partly in relation to advanced age and partly to estrogen deficiency [1]. Overweight and central obesity, diet changes, and lack of exercise concur to alter women's glucose tolerance and increase insulin resistance during the post menopausal period. Impaired glucose tolerance and diabetes mellitus, which are risk factors in the process of CVD, may be found in nearly 20% of women aged 55 to 65 years [2]. Hormone replacement therapy has been shown to mediate clinical cardiovascular risk factors, including reducing body weight [3], increasing insulin-sensitivity [4], and improving blood lipid levels, but the controversial effects of hormone replacement therapy has been overwhelming. It is necessary to find an alternative method to decrease the risk of CVD, which occurs after menopause in women.

Soy is a rich source of the polyphenolic isoflavones genistein and daidzein. Isoflavones are structurally similarly to estradiol and have a high binding affinity for the primary estrogen receptor in the vascular wall. From a research point of view, previous animal research in our team showed that soy isoflavones could decrease body weight and insulin level [5]. Choi et al. [6] found that isoflavone played important roles in the regulation of glucose homeostasis in type 1 diabetic mice. Further cross-sectional studies have suggested that postmenopausal women who consumed a high soy diet had a lower body mass index (BMI) and lower fasting insulin compared to those who consumed no soy [7].

On the basis of laboratory and observational evidence, several longitudinal studies in postmenopausal women have examined the relationship between soy isoflavone supplementation and risk factors for CVD, such as body weight, lipids, and glucose metabolism, but the results are controversial. Some research suggested a reduction in body weight [8], [9], fasting blood glucose [10], [11], and insulin level [10], [11], while others did not [12], [13], [14], [15], [16].

Clinical trial studies used various amounts of isoflavones with various periods of treatment in postmenopausal women. The purpose of this meta-analysis was to synthesize the evidence from randomized controlled trials (RCTs) by performing a meta-analysis to assess the effects of soy isoflavone supplementation on the CVD risk factors such as body weight, fasting blood glucose, and insulin level in non-Asian postmenopausal women.

Section snippets

Literature search

A literature search was carried out in PubMed, EMBASE, and Cochrane databases to identify all relevant RCTs about the effects of soy isoflavone supplementation on body weight, blood glucose, and insulin from 1970 to October 2010 in the non-Asian population. We used the following medical subject heading (MeSH) terms and/or text words: “body weight” [MeSH Terms] AND “isoflavones” [MeSH Terms]; “blood glucose” [MeSH Terms] AND “isoflavones” [MeSH Terms]; “insulin” [MeSH Terms] AND “isoflavones”

Characteristics of studies and quantitative synthesis

A total of 594, 142, and 404 studies were identified from the primary computerized literature search for potential relevant studies. The excluded studies included reviews, animal experiments, duplicated publications, studies not interested in this relationship investigation, and no isoflavone supplemented or combined with other treatments. Finally, 9, 11, and 11 studies for body weight, blood glucose, and insulin levels separately were included for the meta-analysis (Fig. 1). In some studies,

Discussion

A recently published meta-analysis in 2010 by Ricci et al. [22] reported that isoflavone use was not associated with a significant glycemia reduction in perimenopausal and postmenopausal non-Asian women. Our meta-analysis yielded completely significantly different results. In this meta-analysis, significant changes were found in body weight, blood glucose level, and fasting insulin level with soy isoflavone supplementation compared with the placebo control group in the non-Asian postmenopausal

Acknowledgments

This work was supported by the Natural Science Foundation of China (30972439).

References (30)

  • H. Sumino et al.

    Effects of hormone replacement therapy on weight, abdominal fat distribution, and lipid levels in Japanese postmenopausal women

    Int J Obes Relat Metab Disord

    (2003)
  • N.D. Stojanovic et al.

    The effects of transdermal estradiol alone or with cyclical dydrogesterone on markers of cardiovascular disease risk in postmenopausal women with type 2 diabetes: a pilot study

    Angiology

    (2003)
  • Y. Zhang et al.

    Isoflavone reduces body weight by decreasing food intake in ovariectomized rats

    Ann Nutr Metab

    (2009)
  • M.S. Choi et al.

    Genistein and daidzein prevent diabetes onset by elevating insulin level and altering hepatic gluconeogenic and lipogenic enzyme activities in non-obese diabetic (NOD) mice

    Diabetes Metab Res Rev

    (2008)
  • P. Villa et al.

    The differential effect of the phytoestrogen genistein on cardiovascular risk factors in postmenopausal women: relationship with the metabolic status

    J Clin Endocrinol Metab

    (2009)
  • Cited by (77)

    View all citing articles on Scopus

    This work was supported by the Natural Science Foundation of China (30972439) and Youth Fund of Public Health College of HMU.

    View full text