For decades, estrogen was used as a component of hormone replacement therapy to treat menopausal symptoms and for anticipated preventative health benefits in women with prostesterone, or as a monotherapy hormone treatment in women after hysterectomy, but after studies reported that long-term estrogen increase the prevalence of cardiovascular events and breast cancer, many patients and researchers have looked into alternative treatments such as food or products containing phytoestrogens.  Phytoestrogens are weak plant-derived estrogens that are structurally similar to estrogen hormones produced by the body.

The Cochrane Database of Systematic Review studied the effects of phytoestrogens for vasomotor symptoms of menopause.  The authors reviewed trials that were randomized with either peri- or postmenopausal participants with vasomotor symptoms, trials with a duration of at least 12 weeks, and trials where the intervention was a food or supplement with high levels of phytoestrogens, including dietary soy, soy extracts, red clover extracts and other types of phytoestrogens.  Of the thirty trials comparing phytoestrogens with controls that met the inclusion criteria, only a few met a priori inclusion criteria for meta-analysis.  There was no significant difference in the overall frequency of hot flashes when comparing Promensil (a red clover extract) compared to placebo when comparing 5 trials and there was also no significant difference in the percent reduction in hot flashes in 2 trials looking at Promensil and placebo.  Of the remaining studies, a few found a slight reduction in frequency and severity of hot flushes and night sweats compared to placebo, but many of these studies were underpowered and of low quality.  In addition, there was a strong placebo effect in many of the studies.  Overall, there did not appear to be evidence supporting the effectiveness of phytoestrogen treatments in the treatment of menopausal vasomotor symptoms.

Researchers have also looked into the use of flaxseed, also a phytoestrogen, for the management of hot flashes.  One pilot study at the Mayo Clinic enrolled 30 women and studied the effect of ingesting 40grams of crushed flax seed daily for 6 weeks and looking at the change in hot flash score as reported prospectively in a daily hot flash diary.  The mean decrease in the hot flash frequency was 50%- from 7.3 hot flashes to 3.6, and the mean decrease in the hot flash scores was 57%.  This small study suggests that further study is warranted regarding the use of flaxseed as a possible option the treatment of hot flashes.

Natural treatments are often assumed safe, although such treatments require similar rigorous study for safety and efficacy as medications.  From the data thus far, neither efficacy nor safety is established at this time.  Though phytoestrogens are often marketed as “natural” or “safe,” they may have adverse effects and it is essential to consult with a physician prior to starting treatment with phytoestrogens.   In the study at the Mayo Clinic mentioned above, 50% experienced mild or moderate abdominal distention, almost 30% of the participants experienced mild diarrhea, and about 20% withdrew because of side effects.   In addition, because phytoestrogens act similar to estrogen in certain tissues in the body, they theoretically could increase the risk of breast cancer, and overall safety requires further assessment.   Reassuringly, however, the authors in the Cochrane Database Systematic Review did not find evidence that treatment with phytoestrogens causes oestrogenic stimulation of the endometrium when used for up to two years.

Betty Wang, MD


Lethaby AE, Brown J, Marjoribanks J, Kronenberg F, Roberts H, Eden J. Phytoestrogens for vasomotor systems. Cochrane Database of Systematic Reviews 2007, Issue 4. Art. No: CD001395. DOI: 10.1002/14651858.CD001495.pub3

Tice JA, Grady, D. Alternatives to Estrogen for Treatment of Hot Flashes. JAMA 295 (17): 2076-2078, 2006.

Nelson HD, Vesco KK, Haney E, Fu R, Nedrow A, Miller J, Nicolaidis C, Walker M, Humphrey L.  Nonhormonal Therapies for Menopausal Hot Flashes: systematic review and meta-analysis. JAMA 295 (17): 2057-2071, 2006

Pruthi S, Thompson SL, Novotny PJ, Barton DL, Kottschade LA, Tan AD, Sloan JA, Loprinzi CL. Pilot evaluation of flaxseed for the management of hot flashes.  J Soc Integr Oncol. 5(3): 106-112, 2007

Related Posts