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

  • 2025-07-05
  • Maturitas 200
    • Hana Kahleova
    • Tatiana Znayenko-Miller
    • Richard Holubkov
    • Neal D Barnard

Study Design

Type
Randomized Controlled Trial (RCT)
Sample size
n = 84
Population
84 postmenopausal women
Methods
randomly assigned to a low-fat vegan diet supplemented with soybeans or a control group for 12 weeks
Duration
12 weeks
Funding
Unclear

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.

Research Insights

  • Pueraria→Reduced Body Weight

    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). ... The increased consumption of each of the three isoflavones was associated with weight loss (r = -0.67, p < 0.001 for genistein; ...)

    Effect
    Beneficial
    Effect size
    Moderate
  • Pueraria→Reduced Hot Flashes

    The increased consumption of each of the three isoflavones was associated with weight loss ... but not with the reduction in severe hot flashes.

    Effect
    Neutral
    Effect size
    Small
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