Red clover isoflavones are safe and well tolerated in women with a family history of breast cancer

Trevor J. Powles, Anthony Howell, D. Gareth Evans, Eugene V. McCloskey, Sue Ashley, Rosemary Greenhalgh, Jenny Affen, Lesley Ann Flook, Alwynne Tidy

Research output: Contribution to journalArticlepeer-review


Objective. To assess the safety and tolerability of a standardized 40 mg red clover isoflavone dietary supplement (Promensil®, Novogen) in women with a family history of breast cancer to evaluate the feasibility of using the supplement for prevention of breast cancer in healthy women. Study design. Healthy women aged 35-70 years (n = 401) with at least one first-degree relative with breast cancer received red clover isoflavones or placebo for three years in a randomized, double-blind, placebo-controlled pilot trial. Participants were assessed clinically and blood samples taken for biochemical analysis every six months. In addition, study participants underwent mammography, bone density and transvaginal ultrasound (postmenopausal women only) once per year. Results. No significant differences in breast density, endometrial thickness, serum cholesterol, follicle stimulating hormone levels and bone mineral density were detected between those taking red clover isoflavones and placebo. In postmenopausal women, some significant differences in bone marker levels were seen between active and placebo groups, at six months and at 12 months. The adverse event profile was similar across all red clover isoflavone and placebo groups. Conclusion. This three-year study supports the growing body of evidence that treatment with red clover isoflavones is safe and well tolerated in healthy women. Supplements containing red clover isoflavones did not adversely affect breast density, skeletal strength or cardiovascular status. In postmenopausal women, endometrial status was not adversely affected. The adverse event profile was similar between red clover isoflavones, and placebo and endocrine status did not differ.

Original languageEnglish
Pages (from-to)6-12
Number of pages7
JournalMenopause International
Issue number1
Publication statusPublished - 1 Mar 2008


  • Breast cancer
  • Isoflavones
  • Menopause
  • Phytoestrogens
  • Red clover


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