Combined bioavailable isoflavones and probiotics improve bone status and estrogen metabolism in postmenopausal osteopenic women: a randomized controlled trial

Am J Clin Nutr. 2017 Sep;106(3):909-920. doi: 10.3945/ajcn.117.153353. Epub 2017 Aug 2.


Background: Female age-related estrogen deficiency increases the risk of osteoporosis, which can be effectively treated with the use of hormone replacement therapy. However, hormone replacement therapy is demonstrated to increase cancer risk. Bioavailable isoflavones with selective estrogen receptor affinity show potential to prevent and treat osteoporosis while minimizing or eliminating carcinogenic side effects.Objective: In this study, we sought to determine the beneficial effects of a bioavailable isoflavone and probiotic treatment against postmenopausal osteopenia.Design: We used a novel red clover extract (RCE) rich in isoflavone aglycones and probiotics to concomitantly promote uptake and a favorable intestinal bacterial profile to enhance isoflavone bioavailability. This was a 12-mo, double-blind, parallel design, placebo-controlled, randomized controlled trial of 78 postmenopausal osteopenic women supplemented with calcium (1200 mg/d), magnesium (550 mg/d), and calcitriol (25 μg/d) given either RCE (60 mg isoflavone aglycones/d and probiotics) or a masked placebo [control (CON)].Results: RCE significantly attenuated bone mineral density (BMD) loss at the L2-L4 lumbar spine vertebra (P < 0.05), femoral neck (P < 0.01), and trochanter (P < 0.01) compared with CON (-0.99% and -2.2%; -1.04% and -3.05%; and -0.67% and -2.79, respectively). Plasma concentrations of collagen type 1 cross-linked C-telopeptide was significantly decreased in the RCE group (P < 0.05) compared with CON (-9.40% and -6.76%, respectively). RCE significantly elevated the plasma isoflavone concentration (P < 0.05), the urinary 2-hydroxyestrone (2-OH) to 16α-hydroxyestrone (16α-OH) ratio (P < 0.05), and equol-producer status (P < 0.05) compared with CON. RCE had no significant effect on other bone turnover biomarkers. Self-reported diet and physical activity were consistent and differences were nonsignificant between groups throughout the study. RCE was well tolerated with no adverse events.Conclusions: Twice daily RCE intake over 1 y potently attenuated BMD loss caused by estrogen deficiency, improved bone turnover, promoted a favorable estrogen metabolite profile (2-OH:16α-OH), and stimulated equol production in postmenopausal women with osteopenia. RCE intake combined with supplementation (calcium, magnesium, and calcitriol) was more effective than supplementation alone. This trial was registered at as NCT02174666.

Keywords: bioavailability; bone density; bone turnover; equol; isoflavone; osteopenia; postmenopause; probiotics.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Biological Availability
  • Bone Density / drug effects*
  • Bone Density Conservation Agents / pharmacology
  • Bone Density Conservation Agents / therapeutic use
  • Bone Diseases, Metabolic / drug therapy*
  • Bone Diseases, Metabolic / metabolism
  • Bone Remodeling / drug effects*
  • Bone and Bones / drug effects*
  • Bone and Bones / metabolism
  • Collagen Type I / blood
  • Double-Blind Method
  • Drug Combinations
  • Estrogens / deficiency
  • Estrogens / metabolism*
  • Female
  • Gastrointestinal Microbiome
  • Humans
  • Intestinal Mucosa / metabolism
  • Intestines / drug effects
  • Intestines / microbiology
  • Isoflavones / blood
  • Isoflavones / pharmacokinetics
  • Isoflavones / pharmacology
  • Isoflavones / therapeutic use*
  • Middle Aged
  • Osteoporosis, Postmenopausal / metabolism
  • Osteoporosis, Postmenopausal / prevention & control
  • Peptides / blood
  • Phytotherapy
  • Plant Extracts / pharmacology
  • Plant Extracts / therapeutic use
  • Probiotics / therapeutic use*
  • Selective Estrogen Receptor Modulators / pharmacology
  • Selective Estrogen Receptor Modulators / therapeutic use
  • Trifolium / chemistry


  • Bone Density Conservation Agents
  • Collagen Type I
  • Drug Combinations
  • Estrogens
  • Isoflavones
  • Peptides
  • Plant Extracts
  • Selective Estrogen Receptor Modulators
  • collagen type I trimeric cross-linked peptide

Associated data