Isoflavones and changes in body weight and severe hot flashes in postmenopausal women: A secondary analysis of a randomized clinical trial

Abstract

Objective: Severe hot flashes have been associated with an increased risk of cardiovascular disease and diabetes. This secondary analysis assessed associations between isoflavone intake, body weight, and severe hot flashes in postmenopausal women.

Methods: Participants (n = 84) were randomly assigned to a low-fat vegan diet supplemented with soybeans (n = 42) or a control group who made no changes to their diet (n = 42) for 12 weeks. Three-day diet records were analyzed using the Nutrition Data System for Research software. A repeated measures analysis of variance, Spearman correlations, and a linear regression model were used for statistical analyses.

Results: Daidzein intake increased in the vegan group (effect size: +34.4 mg/day [95 % CI +28.1 to +40.8], p < 0.001). Similarly, genistein and glycitein increased in the vegan group (effect sizes: +34.8 mg/day [95 % CI +27.7 to +42.0], p < 0.001; and +4.2 mg/day [95 % CI +3.2 to +5.2], p < 0.001, respectively). Mean body weight decreased by 3.6 kg in the vegan group and by 0.2 kg in the control group (effect size: -3.4 kg [95 % CI -4.5 to -2.3], p < 0.001). Severe hot flashes were reduced by 92 % (from 1.3/day to 0.1/day) in the vegan group (p < 0.001) and did not change significantly in the control group (between-group p = 0.02). The increased consumption of each of the three isoflavones was associated with weight loss (r = -0.67, p < 0.001 for daidzein; r = -0.67, p < 0.001 for genistein; and r = -0.66, p < 0.001 for glycitein), but not with the reduction in severe hot flashes. There was no significant association between weight loss and a reduction in severe hot flashes (r = +0.20, p = 0.12). Controlling for energy intake and changes in body mass index, the main independent predictor of a reduction in severe hot flashes was the increased intake of daidzein (p = 0.04). Controlling for fiber and fat intake did not change the results.

Conclusions: These findings suggest that the mechanisms by which a low-fat vegan diet supplemented with soybeans reduces the frequency of severe hot flashes include the increased consumption of daidzein, among other potential factors. Confirmatory trials are needed.

Trial registration: ClinicalTrials.gov, NCT04587154, registered on Oct 14, 2020.

Keywords: Daidzein; Genistein; Glycitein; Hot flashes; Isoflavones; Nutrition; Plant-based; Vegan; Weight.