A controlled 2-mo dietary fat reduction and soy food supplementation study in postmenopausal women

Abstract

Background: Low intake of dietary fat and high intake of soy foods have been suggested to partly explain the lower breast cancer rates in Asia, perhaps because of lower endogenous estrogens. Objective: The objective was to assess the hormonal and nonhormonal effects of diets resembling an Asian diet in terms of total fat and soy food contents. Design: Fifty-seven postmenopausal women participated in a randomized, controlled, dietary intervention study. The subjects consumed a very-low-fat diet (VLFD; 11% of energy as fat), a Step I diet (25% of energy as fat) supplemented with soy food (SFD; 50 mg isoflavones/d), or a control Step I diet (CD; 27% of energy as fat) with no soy food. All diets were prepared at the General Clinical Research Center of the University of Southern California. Serum hormones and other markers were measured at baseline and every 2 wk during the 8 wk of intervention. Results: There were no significant differences in total estradiol and sex hormone binding globulin at the completion of the intervention between women in the SFD and VLFD groups and those in the CD group. Serum insulin decreased significantly in the SFD group, and leptin decreased significantly in the SFD and VLFD groups; however, these changes did not differ significantly from the changes in the CD group. Conclusions: This study does not provide evidence that ingestion of soy food or a VLFD significantly reduces estrogen concentrations in postmenopausal women. However, short-term changes in diet may have significant and beneficial effects on blood insulin and leptin concentrations.Am J Clin Nutr 2005;81:1133-41.

Dietary patterns, the Alternate Healthy Eating Index and plasma sex hormone concentrations in postmenopausal women

“…Although one observational study found that higher soy intake was associated with lower serum levels of estrogens, 29 randomized trials in general did not observe any effect. 30,31 However, a 30 g soy milk powder supplement increased SHBG concentrations in a 10-week trial. 32 Soy intake is a component of the AHEI, however, the 1990 FFQ only assessed soy bean or tofu intake and may underestimated intake of soy from soy milk and foods containing soy protein.…”

Phytoestrogen Exposure Is Associated with Circulating Sex Hormone Levels in Postmenopausal Women and Interact withESR1andNR1I2Gene Variants

“…Human intervention and cross-sectional studies that have investigated the effect of phytoestrogens or soy intake on hormone levels in postmenopausal women have been small and produced inconsistent results (4,(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38). This study is the largest study ever conducted to investigate the relationship between phytoestrogen exposure and circulating sex hormone levels in postmenopausal women.…”

Epidemiology of soy exposures and breast cancer risk

“…There is suggestion in some cross-sectional studies that circulating oestrogen and androgen levels may be nonsignificantly decreased in association with high-soy food intake but these effects are typically small and the results are not consistent. Results from the nearly 20 shortterm intervention studies on soy (mainly given as supplements or other soy protein products) and circulating oestrogen and sexhormone-binding globulin are mixed and this may be related to differences in study design, small sample sizes, the amount and source of soy isoflavones that were used, duration of supplementation and other reasons (for a review, see Maskarinec et al, 2004;Wu et al, 2005). Fewer studies have investigated the effect of soy intake on mammographic density.…”