Supplementation of soy isoflavones improved sex hormones, blood pressure, and postmenopausal symptoms

J Am Coll Nutr. 2015;34(1):42-8. doi: 10.1080/07315724.2013.875434. Epub 2015 Feb 3.


Objective: The present study is aimed at determining the effect of supplementing the diet of postmenopausal women with soy isoflavones on blood pressure and hormonal levels and providing relief from symptoms.

Method: This research was conducted in Imam Khomeini Hospital, Ahvaz, Iran. In this double-blind experimental controlled study, 61 postmenopausal women were randomly assigned to either an experimental group (soy isoflvone, n = 30) or control group (placebo, n = 31). The subjects in the experimental group were given a supplementation of 33 g of soy in the form of biscuits that contained approximately 54 mg isoflavones for a period of 8 weeks.

Results: Soy isoflavones supplementation made a significant difference in the severity and intensity of symptoms as determined by the Kuppermann index. On supplementation with soy the intensity of symptoms among the subjects decreased significantly and the mean total score from 26.8% at pre phase decreased to 9.38% at post phase (p < 0.001). In the present study, the level of follicular stimulating hormone (FSH) and luteinizing hormone (LH) in the experimental group decreased after intervention with soy. This reduction in FSH and LH was highly significant as tested by repeated measures analysis of variance (ANOVA; p < 0.001). After intervention with soy, a slight reduction in systolic and diastolic blood pressure was recorded in the experimental group, indicating the beneficial effect of soy isoflavones on regulating blood pressure.

Conclusion: This study suggests that soy supplementation could be recommended as an alternative therapy to hormone replacement therapy for control of postmenopausal symptoms.

Keywords: menopausal women; soy isoflavones; supplementation; symptoms.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blood Pressure / drug effects*
  • Dietary Supplements*
  • Double-Blind Method
  • Female
  • Follicle Stimulating Hormone / blood*
  • Humans
  • Iran
  • Isoflavones / therapeutic use*
  • Luteinizing Hormone / blood*
  • Middle Aged
  • Postmenopause / blood
  • Postmenopause / drug effects*
  • Postmenopause / physiology
  • Soybean Proteins / therapeutic use*


  • Isoflavones
  • Soybean Proteins
  • Luteinizing Hormone
  • Follicle Stimulating Hormone